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8332

Volume 104

Number 2

Summer 2018

Journal of the

WASHINGTON Tee

SEP 26 2018

HAR VAIKD

UNIVERSITY

ACADEMY OF SCIENCES

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ISSN 0043-0439 Issued Quarterly at Washington DC

Spring 2018

EDITOR’S COMMENTS

Presenting the 2018 Simmer issue of the Journal of the Washington

Academy of Sciences.

For this issue we have two papers, both in astronomy. The first

discusses an anomalous feature in the Milky Way, our home Galaxy. The

second discusses a new measurement of a neutrino traveling over four

billion light years.

The Summer issue also includes the Outgoing and Incoming

Presidents’ Messages to the Academy as well as the 2018 awardees.

The Journal is the official organ of the Academy. Please consider

sending in technical papers, review studies, announcements, and book

reviews.

Letters to the editor are encouraged. Please send email

(wasjournal@washacadsci.org) comments on papers, suggestions for

articles, and ideas for what you would like to see in the Journal. We are a

peer reviewed journal and need volunteer reviewers. If you would like to be

on our reviewer list please send email to the above address and include your

specialty.

Sethanne Howard

Washington Academy of Sciences

ill

Journal of the Washington Academy of Sciences

Editor Sethanne Howard showard@washacadsci.org

Board of Discipline Editors

The Journal of the Washington Academy of Sciences has an 11-member

Board of Discipline Editors representing many scientific and technical

fields. The members of the Board of Discipline Editors are affiliated with a

variety of scientific institutions in the Washington area and beyond —

government agencies such as the National Institute of Standards and

Technology (NIST); universities such as Georgetown; and professional

associations such as the Institute of Electrical and Electronics Engineers

(IEEE).

Anthropology Emanuela Appetiti eappetiti@hotmail.com

Astronomy Sethanne Howard sethanneh@msn.com

Biology/Biophysics Eugenie Mielczarek mielczar@physics.gmu.edu

Botany Mark Holland maholland@salisbury.edu

Chemistry Deana Jaber djaber@marymount.edu

Environmental Natural

Sciences Terrell Erickson terrell.erickson! @wdc.nsda.gov

Health Robin Stombler rstombler@auburnstrat.com

History of Medicine Alain Touwaide atouwaide@hotmail.com

Operations Research Michael Katehakis mnk(@rci.rutgers.edu

Science Education Jim Egenrieder jim@deepwater.org

Systems Science Elizabeth Corona elizabethcorona@gmail.com

Spring 2018

Washington Academy of Sciences

Weaver's “Jet” and High-Velocity Cloud Complex H

Two Dwarf Satellite Galaxies of the Milky Way Seen in

the HI 21-cm Line

S. Christian Simonson, III

Lawrence Livermore National Laboratory, Retired

Abstract

Two anomalous-velocity HI features, Weaver’s “jet” and High-Velocity

Cloud Complex H (HVC H), appear to be good candidates for dwarf satellites

of the Milky Way. These features are modeled as HI disks in dark matter halos

that move in orbits around the Milky Way. The current /,b, Vsr appearance of

the tidal features they develop as they approach the Milky Way indicate

distances of 108 + 36 kpc for Weaver’s “jet” and 27 + 9 kpe for HVC H. As

these are within the distances to known Milky Way satellites, finding stellar

components might be possible and would be of interest for the star formation

history of the Milky Way. For Weaver’s “jet”, covering 2° x 7° at / = 197.3°,

b =+2.1°, Vise = -30 to -87 km s“, the dark matter mass is estimated as 1.8 +

0.6 x 10° Mo. The disk HI mass is 1.2 + 0.8 x 10’ Mo. For HVC H, covering

6° x 7° at / = 130.5°, b = +1.5°, Vise = -202 km s", the dark matter mass is

estimated as 5.2 + 3.5 x 10° Mo. The previously estimated HI mass is 6.4 x

10° Mo.

1. Introduction

1.1 Purpose

THE PURPOSE OF THIS RESEARCH is to see if certain anomalous-velocity HI

features, namely Weaver’s “jet” (Weaver 1974, Simonson 1975) and High-

Velocity Cloud Complex H (HVC H) (Blitz et al. 1999), could be interpreted

as rotating HI disks in dark matter halos which have undergone tidal

evolution while orbiting in the gravitational potential of the Milky Way with

perturbations by M31. There have been several previous interpretations of

these features, such as a “jet” (Weaver 1974) or a cloud in an inclined

retrograde orbit for HVC H (Lockman 2003). Based on current knowledge,

such features appear to be the rotating-disk stage of the accretion of gas in a

dark matter halo. If substantiated, this interpretation could lead to improved

understanding of such dwarf galaxies and their debris streams around the

Milky Way.

Summer 2018

1.2 History

When high-resolution HI observations of external galaxies first

became available from aperture synthesis radio telescopes in the mid-1970s,

astronomers could map out the distribution of neutral hydrogen and measure

rotation curves in these galaxies with the same sort of accuracy as in the

Milky Way. One particularly good example was the edge-on galaxy NGC

891. Its rotation curve has a range of about +200 km s! (Sancisi and Allen

1079):

Along the plane of our own Milky Way, a similar pattern in H I was

noticed in Weaver’s “jet”. This feature was known from the H I 21-cm line

survey within 10 degrees of the galactic plane by Weaver and Williams

(1974). Here the velocity amplitude was less, reaching from the edge of local

neutral hydrogen at about -20 km s' to -87 km s''. At its galactic longitude

of 197°, these velocities are anomalous. That is, they cannot be represented

by hydrogen in circular orbits in the plane of the Milky Way.

Using NGC 891 as an example, it was natural to make a simple

analytical model of a disk galaxy satellite passing by the Milky Way. As the

Toomres (1972) had found with MS1, tidal effects were seen. By comparing

the calculated tidal tail with another well-known 21-cm line feature, a

streamer of HI clouds that crossed the anti-center direction, / = 180°, at an

incoming and totally non-circular velocity of -90 km s', a distance of 17

kpe was indicated.

One thing that was a puzzle was the lack of any optical or radio

continuum features in this direction. If it were a galaxy, why were there no

galactic nucleus or star clusters or HII regions detected? It’s true that at its

low galactic latitude of 2° it was in the so-called zone of avoidance, a region

near the galactic plane where no external galaxies were seen. Of course,

individual stars were expected to be confused with Milky Way stars, but

these common optical tracers of external galaxies should have been visible.

The author along with his students and colleagues spent hours poring

over the prints of the Palomar Observatory Sky Survey searching for non-

stellar images. To no avail.

What we didn’t realize was we were peering into a dark matter halo.

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A few years later, astronomers, Vera Rubin in particular, established

the existence of dark matter. The mass of the Milky Way was thereby

increased by a factor of 10. That meant that distances depending on tidal

effects would also be ten times larger.

We also had to reconsider our analytical models. Instead of making

the simple assumption of a zero-energy orbit, which was the equivalent of

letting a satellite approach from infinity, orbits had to be confined within the

Local Group. The net result was an increase in the distance by a factor of

Six, instead of ten, to 108 kpc.

Looking around, if this approach seemed to work for Weaver’s “jet”,

why not consider another well-known anomalous-velocity object, HVC H?

It bore many of the same characteristics and seemed to be worth analyzing.

2. Method

2.1 Summary of Orbit and Disk Calculation Approach

This work uses recent Hubble Space Telescope results on M31 (van

der Marel et al. 2012a, b) to calculate the time-dependent center-of-mass

(CM) locations and the dark matter mass distributions of the Milky Way and

M31. Time-dependent CM orbits of the satellites have been computed in 3D,

along with rings of test particles representing their disks. Tidal effects that

develop on these rings are compared with published data in order to estimate

their distances.

2.2 Time-Dependent Gravitational Field

We use mass distribution parameters for the Milky Way and M31

taken from van der Marel ef al. (2012a) (their Paper IH) and (2012b) (their

Paper III). They adopted the distance of the Sun from the Galactic center as

8.29 kpc and the local standard of rest (LSR) circular velocity as 239 kms",

and we have used these values.

Van der Marel ef a/. (2012a) reported a separation of 774 +40 kpc of

M31 from the Milky Way and a relative velocity of —110.6 +4.4 km s?. A

key result of this paper is that “the velocity vector of M31 is statistically

consistent with a radial (head-on) collision orbit toward the Milky Way”.

This means that the radial velocity represents the total velocity for kinetic

energy and orbital considerations.

Summer 2018

In their Paper III (van der Marel e¢ a/. 2012b), they slightly revised

their set of Hernquist-type mass distribution parameters for the Milky Way

and M31 to be consistent with the timing argument presented in Paper II

(van der Marel et al. 2012a). The set we have adopted here for both galaxies

is their Hernquist-type mass parameter My = 2.04 x 10'* Mo and radial scale

length parameter r = 62.5 kpc. They also took the age of the universe as

13.75 + 0.11 Gyr, which we have also adopted. We’II explain the use of the

Hernquist formula shortly. (Values used by other researchers could also be

used, subject to satisfying the timing argument.)

What van der Marel ef al. (2012a, b) were using was the concept of

conservation of energy. In a closed system such as the Local Group, the total

energy is the sum of the kinetic energy and the potential energy. The

potential energy due to gravity depends on the masses and their separation.

The kinetic energy depends on the masses and their velocities. So, taking the

two dominant masses, the Milky Way and M31, if we have a measurement

of their masses from the orbits of the stars and gas they contain, and if we

can measure their separation and mutual velocity, as van der Marel and

coauthors did, then we can verify the mass measurements by requiring that

the two galaxies turn around at half the age of the universe. That is, the force

of the gravitational attraction between them must be just strong enough so

that, running time backward, they came to a halt at that time.

By integrating the equations of motion backwards for the Milky Way

and M31, starting with their current separation and velocity as initial

conditions, we have the time locations of the two most massive bodies in the

Local Group. This gives us a first-order approximation for the gravitational

potential as a function of time.

We consider that M33 and the Magellanic Clouds, being 10% less

massive, would produce only second-order effects in the main galaxy field.

We have chosen to ignore these for the present calculations.

2.3 Orbit Calculations

Having the time-dependent gravitational field, we can integrate the

equations of motion for the CMs of the satellites. The initial conditions

include their measured line-of-sight (7.e., radial) velocity with respect to the

local standard of rest, Visr, their present location as given by their galactic

longitude, /, and latitude, b, together with a value of the distance, d, which

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we choose. What we don’t have is any measurement of the velocity at right

angles to the line of sight. So we take this so-called orthogonal velocity and

vary it until the computed orbit returns to its original radius at the origin of

the time calculations. The result is a table of satellite CM locations versus

time.

The CM orbits are three-dimensional. In their current locations, for

Weaver’s “jet”, the gravitational attraction due to M31 is 3% of that for the

Milky Way at present, reaching 15% by t = —6.9 Gyr. For HVC H that due

to M31 is 1.3% of that for the Milky Way, but it reaches 19% by t = —6.1

Gyr. The reason for the larger effect as M31 and the Milky Way separate

going backward in time is that the distance from a satellite to M31 gets

comparable with its distance to the Milky Way. Also, thanks to the 3D

character of the satellite orbits, the maximum effects are offset from the mid-

point (7.e., the turn-around point) of M31’s orbit.

2.4 Disk Calculations

If one thinks of these HI features as arising from rotating disks in

dark matter halos, then one can measure the rotation curve and set the halo

in motion around the Milky Way. The basic assumption is that we are

viewing a circular disk projected on the line of sight. A rotation curve can

be found from the HI 21-cm line data by projecting the maximum Vzsr

velocities in each scan onto the axis of the satellite disk.

We then fit the circular velocities vs radius, using the principle of

least squares. This assumes that the neutral hydrogen gas rotating in the disk,

no matter how lumpy, traces out an underlying smooth mass distribution, in

this case a dark matter halo. In our case the circular velocities are fit with a

Hernquist-type dark matter mass distribution. (The Hernquist formula is

convenient for these calculations, following the example of van der Marel ef

al. 2012a, b, but alternative formulations could also be employed.) The

rotation curve fitting results in two parameters, MH for the mass and rH for

the radial extent. The gravitational acceleration at a radius r is given by the

Hernquist formula for the mass within that radius, namely, a(r) = -G Mu/(r

+ rv)’. (One useful characteristic of the Hernquist formula, as noted by van

der Marel and coauthors, is that at large radii the mass remains finite.)

We represent the disk of each satellite by a series of rings of massless

test particles initially orbiting in circular orbits. For comparison with the HI

Summer 2018

observations, the test particles are placed along three equally spaced rings,

with angular spacing such that the particles represent equal areas. This

allows some evaluation of velocity crowding and smearing effects in the line

profiles at the final location. They are set in circular motion with velocities

corresponding to the mass contained within their radius. The equations of

motion are then integrated inward until the CM arrives at its present location.

2.5 Tidal Effects

As the satellite CM travels along its orbit, the outer particles reach a

tidal radius, defined as the point where the attraction of the satellite mass is

equal to that of the Milky Way. As the satellite continues along its path, the

outer particles will feel a stronger attraction to the large galaxy and become

detached. As the separation from their host satellite increases, these particles

eventually follow their own orbits around the Milky Way.

We have noted that the acceleration due to M31 can reach 15% of

that of the Milky Way for Weaver’s “jet” and 19% of that for HVC H. As

these are significant perturbations, in the two-body system formed by the

Milky Way plus M31, the test particle orbits for tidally detached particles

are found to exhibit chaotic characteristics. Representative particles are then

used to trace the orbits.

At the end of the integration, the test particle locations and velocities

are converted to /,b,Visr values and compared with 21-cm line data. The

orientations of the rings are adjusted to give the best match. For Weaver’s

“Yet” the disk is found to be at an angle of 20°, while for HVC H we use

Lockman’s tilt angle of 45°. From the appearance of the tidal effects, for

Weaver’s “jet” we are viewing the bottom of the disk, while for HVC H we

are viewing the top. In both cases the CM orbits are prograde, meaning in

the direction of galactic rotation, and the disk rotations are also prograde.

The orbits are lying almost in the galactic plane.

2.6 Weaver's “Jet”

From Simonson (1975), for the feature known as Weaver’s “jet”, the

region of anomalous velocity identified as a disk covers approximately 2° x

7°, centered at / = 197.3°, b =+2.1°. This is shown in Figure 1 as a latitude

vs longitude plot of its appearance on the sky. From this location, an

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elongated string of H I concentrations stretches more than 40° across the sky

between latitudes b = +5° and +10° to around longitude / = 155°.

10 #

5 |

‘s "Jet'

5 | a |

200 190 180 170 160 150

Galactic Longitude (degrees)

Figure 1: Weaver’s “jet” and anti-center HI streamer in latitude vs longitude diagram of

contours of HI column density, Nu, beyond the cutoff velocity of Milky Way HI (Simonson

1975). Contours were obtained by summing the product of brightness temperature and

velocity increment, 7b AV, in the contour maps of Weaver and Williams (1974). Contour

units are 3.6 x 10!° cm? with the lowest at 0.2x and then linearly from 1x to 6x (highest).

The line-of-sight velocity ranges from about Visr = —30 km s“, near

the edge of local Milky Way HI radiation, to about Vise = —87 km s™". The

central velocity used here is Visr = —45 kms‘. As is shown in the longitude-

velocity plot of Figure 2, the elongated string of HI concentrations stretching

from this location crosses the anti-center direction, / = 180°, near Visr = —90

kins *.

Summer 2018

Visr (km $s“)

210 200 190 180 170 160 150 140

Galactic Longitude (degrees)

Figure 2: Weaver’s “jet” and anti-center HI streamer—longitude-velocity plot of

contours of 7;(/,Visr) in units of 1.18 K (Williams 1973) found by projecting the greatest

extent of the contours in Weaver and Williams’s (1974) maps. Overlaid on the data are the

calculated /, Vzsr points for test particles that represent the tidal debris tail for CM distances

of 72 kpc (circles) and 144 kpc (squares) at regular mass, reduced mass (smaller symbols),

and increased mass (triangles).

In the current analysis, the anti-center streamer 1s identified as a tidal

tail. For Weaver’s “jet” the angle of inclination is only 10°. That is to say,

we are viewing it almost edge-on. Nevertheless, as the number of available

points from the survey grid is small, the formal fitting errors are large,

amounting to +66% in the mass.

2.7 High-Velocity Cloud Complex H

HVC H has been studied by Blitz et al. (1999) and by Lockman

(2003). These authors provide latitude-longitude maps of the object, which

is centered at / = 130.5°, 5b =+1.5° (Figure 4 in Blitz et al. 1999, Figure 1 in

Lockman 2003). What Lockman (2003) calls the “core” of HVC H occupies

a region about 6° x 7°, with an axial ratio of 4° x 6°, and an angle of 45° for

the major axis of the disk, tilting upward from the right with respect to the

galactic plane. The axial ratio indicates we are viewing it almost face-on;

therefore the correction factor relating line-of-sight velocity in the data to

rotational velocity in the model amounts to 2.4. With this large correction

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factor and the small number of points, the errors can be large. The formal

fitting error in the rotation curve parameters amounts to +67% in the mass.

The data points and the rotation curve are shown in Figure 3.

—+4 ee

ZA ‘m

pees

4.00

Galactic Latitude

-4.00

-240.00 -220.00 -200.00 -180.00 -160.00

Line-of-Sight Velocity

Figure 3: Latitude-velocity plot of line-of-sight velocity (i.e., Vise) points in km s™

representing the locations of the contour edges at each latitude scan from Lockman (2003),

together with the Hernquist-type rotation curve fit to those points for the disk region from

b = -1.0° to +4.5°, i.e., -2.5° to +3.0° from central latitude +1.5°. Lockman’s “Tail” region

is outlined. Tidally detached points originally in rings at +4.5°, +6.0°, and +7.5° from the

CM are shown as calculated for distances 27 and 50 kpc plus +9.0° for 27 kpc. Two

additional points are shown for the final main point at 27 and 50 kpc, indicating the effects

of +67% AM.

Lockman considered it as a gaseous object in an inclined retrograde

orbit in the Galaxy and found a distance of 27 kpc. Blitz et al. (1999)

suggested 50 kpc in order to have this object lying beyond the galactic disk.

The present model of a rotating disk in a dark matter halo has a completely

different basis. By comparing the two initial distances, the present model

favors 27 kpc over 50 kpc. This is based on tidally detached test particles for

that distance appearing in the region of Lockman’s “Tail” feature (shown in

Figure 3).

Summer 2018

3. Results

3.1 Weaver’s “Jet”

For Weaver’s “jet”, from the /,Vzsr plot shown in Figure 2, the

distance is estimated as 108 + 36 kpc. The corresponding dark matter mass

is estimated as Mi = 1.8 + 0.6 x 10° Mo. The radial scale length parameter,

rH, 1s 1.22 kpc. The HI mass for disk plus streamer is 1.6 + 1.1 X 108 Mo, or

6% to 12% of the satellite halo mass. For the disk alone, the HI mass is 1.2

+ (0.8 xX 10’ Mo, or 0.6% + 0.1% of the halo mass.

3.2 High-Velocity Cloud Complex H

For HVC H at / = 130.5°, b = +1.5°, the central velocity is found to

be Visr = -202 kms". By fitting the rotation curve, the Hernquist dark matter

halo mass, Mu, is estimated as 1.2 + 0.8 x 109 Mo, and the radial scale length

parameter, rH, is 0.28 kpc. The previously estimated H I mass from

Lockman (2003) is 6.4 x 10° Mo, or 0.5% of the newly derived satellite

mass. If we move out to 50 kpc, then the dark matter mass would be 2.2 x

10° Mo. The H I mass from Blitz et al. (1999) is 9.0 x 107 Mo, or 0.4% of

the satellite mass at that distance.

4. Conclusions

4.1 Analysis Using Halo-Disk Model Accounts for 21-cm Line

Observations

These calculations show that the HI 21-cm line features studied here

can be accounted for as HI disks in dark matter halos. While Weaver’s “jet”

was described by Simonson (1975) as a new galaxy, HVC H has until now

been treated as a gas cloud. The current success in modeling it as a disk in a

dark matter halo suggests it could be reinterpreted as a dwarf galaxy. The

current approach affords a measurement of its mass directly from the

assumed HI rotation curve.

One should note that the rotating disk model used here is highly

simplified, since it consists of only gravitational forces, without inclusion of

any gas dynamical effects such as those that were treated extensively by

Lockman (2003) and that could be important in the postulated accretion

process.

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The accuracy of rotation-curve modeling is limited in both these

cases by non-optimal alignment of the data grid with the geometry of the

assumed disk. In particular, the results for HVC H could be improved by

taking radial velocity points along the major axis instead of having to rely

on the published 4, V slice.

4.2 Detections of Stars are Possible but may be Problematical

For these objects, their angular sizes, masses, and distances place

them within the range of these parameters for known Milky Way dwarf

satellites. At their low galactic latitudes there can be confusion with Milky

Way stars and obscuration by dust, both along the line of sight and internal

to the objects. However, techniques that have proved successful at revealing

the stars in ultra-faint dwarfs, such as Willman | in Sloan Digital Sky Survey

data (Willman et al. 2011), may be useful in revealing stars in these two

cases.

If a stellar component can be identified, it could have interesting

implications for the star formation history of the Milky Way. In the case of

HVC H, owing to its disk angle of 45°, tidal debris is thrown upward,

forming the “Tail” feature in Lockman’s 5, V slice. This would presumably

contribute to a halo star stream. In the case of Weaver’s “jet”, the streamer

represents accreting material for the galactic disk.

As to whether a stellar component should be expected, recent results

on compact HI sources by Janesh ef al. (2017) and by Janowiecki et al.

(2015) may be applicable to this question in view of the neutral hydrogen

masses found here. Our results are 6.4 x 10° Mo for HVC H at a distance of

27 kpc or 9.0 x 10’ Mo at 50 kpc from previous studies, and 7.3 x 10’ to 2.9

x 10° Mo for disk plus streamer for Weaver’s “jet” at distances of 72 to 144

kpc.

In their investigations, Janesh et al. (2017) detected a stellar

component to AGC 249525 at an HI mass of around 3.2 x 10° Mo.

Janowiecki et al. (2015) reported a positive detection for the HI 1232+20

system at an HI mass of 7.2 x 10° Me but not at 2.0 x 10° or 1.2 x 10° Mo.

They suggested, “these HI sources may represent both sides of the threshold

between ‘dark’ star-less galaxies and galaxies with stellar populations.” The

neutral hydrogen masses for the objects studied here are in this

neighborhood, but lower for HVC H. Also, HVC H has a “lumpy” HI

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distribution as compared with the smoother HI distribution of the typical

ultra-compact high-velocity cloud. It is hard to know if this would be

favorable or unfavorable for detection of a stellar component. However, as

the HI masses of the two candidates studied here are in this neighborhood,

detections should be considered a possibility.

4.3 Summary—H I Features as Dwarf Galaxies

In summary, these calculations show that the HI 21-cm line features

studied here can be accounted for as HI disks in dark matter halos, thus as

satellite dwarf galaxies. At the distances and masses found here, they present

possible targets for photometric research. Successful detection could lead to

better understanding of dwarf galaxy and star formation history in the Local

Group.

Acknowledgements

The author is grateful to Leo Blitz for bringing Lockman’s work on

HVC H to his attention and for many helpful discussions and suggestions

over the course of several years.

References

Blitz, L., Spergel, D. N., Teuben, P., Hartmann, D., & Burton, W. B.

1999, ApJ, 514, 818

Janesh), W.. Khode, KU. Salzer, J.J; eral. 2017, Apy, $37, L1G

Janowiecki, S., Leisman, L, Jozsa, G., et al. 2015, ApJ, 801, 96

Lockman, F. J. 2003, ApJ, 591, L33

Sancisi, R., & Allen, R. J. 1979, Astr. and Ap., 74, 73

Simonson, S.C. 1975, ApJ, 201, L103

Toomre, A., & Toomre, J. 1972, ApJ, 178, 603

Van der Marel, R. P., Fardal, M., Besla, G., et al. 2012a, ApJ, 753, 8

Van der Marel, ik. P...Besla; G:, Cox,.1.J., Sohn,S, T.,.d¢ Anderson, J.

2012b, ApJ, 753, 9

Weaver, H. 1974, in AU Symp. 60, ed. F. J. Kerr & S. C. Simonson, III

(Dordrecht: Reidel), 573

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Weaver, H., & Williams, D. R. W. 1974, Astr. and Ap. Suppl., 17, |

Williams, D. R. W. 1973, Astr. and Ap. Suppl., 8, 505

Willman, B., Geha, M., Strader, J., et al. 2011, AJ, 142, 128

Bio

The author received the S.B. degree in physics from MIT in 1960 and a Ph.D.

in astronomy from Ohio State University in 1967. Following a post-doc at

Leiden Observatory, he joined the faculty of the University of Maryland.

Eventually he retired as a physicist from the University of California

Lawrence Livermore National Laboratory in 2007.

Summer 2018

Washington Academy of Sciences

Multi-Messenger Astronomy — To Catch a Ghost

Sethanne Howard

US Naval Observatory/retired

Abstract

A single neutrino captured by The IceCube Observatory at the South Pole

solves an old mystery: where do cosmic rays come from. That neutrino

was tracked back to a blazar, a supermassive black hole that produces

relativistic particles including cosmic rays. Cosmic rays now have at least

one celestial source.

Introduction

NEUTRINOS ARE EVERYWHERE. They permeate all of space. Do not let it

worry you though. These tiny particles barely interact with anything. In

fact, they can even pass through the entire Earth without being affected.

Neutrinos are the second most abundant type of particle in the universe,

after photons (light particles). If you held your hand toward the sky, about

a billion neutrinos from the Sun would pass through it in a single second.

Neutrinos are fundamental particles that were formed in the first

second of the early universe, even before atoms could form. They are also

continually being produced in the nuclear reactions of stars, like our Sun,

and nuclear reactions here on Earth. Neutrinos are so named because they

are uncharged (or “‘neutral”’) and infinitesimally puny (about a millionth of

the mass of an electron). Neutrino actually means “little neutral one.”

Most of what we call matter is not solid. If a hydrogen atom were

the size of Earth, the single proton at its center would fit inside the Ohio

State football stadium. The electron orbiting it would be even smaller, and

a neutrino could be compared to a single ant zooming by the stadium.

Because of the neutrinos’ elusive behavior, their existence was not

even known until 1959; although, they had been predicted in 1931.

Wolfgang Pauli first predicted the neutrino in order to account for the

apparent loss of energy and momentum that he observed when studying

radioactive beta decays (see Figure 1). Beta decay occurs when a neutron

(n) decays to a proton (p), an electron (e°), and additional energy and

momentum. He predicted that the energy was being carried off by some

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unknown particle. Neutrons and protons are made of quarks. A neutron is

made of an up quark and two down quarks. In beta decay a down quark

flips to an up quark.

A pecuiree Sonays 40 & footed, an cloctres, and

an antingetring vis 4 certua! (mediating) W

boxe This is neutron 2 decay.

Figure | — beta decay. u is an up quark, d is a down quark

Then in 1959 Clyde Cowan and Fred Reines finally found a particle

that fit the description of the proposed neutrino by studying the particles

created by a nuclear power plant. Their study revealed the electron

neutrino. According to the standard model (the standard model is the

theory describing three of the four known fundamental forces (the

electromagnetic, weak, and strong interactions, and not including the

gravitational force)) each “flavor” of neutrino has a corresponding charged

particle from which it gets its name. So the electron neutrino has the

electron as its corresponding charged particle.

In 1968 the first experiment to attempt to detect electron neutrinos

from the Sun used a detector in the bottom of the Homestake mine in South

Dakoda. However they detected neutrinos only about twice a week.

Predictions claimed that the detector should find about one of the 10'° solar

neutrinos a day. This unexplainable lack of solar neutrinos detected

became known as the Solar Neutrino Problem.

The next big discovery was that of the muon neutrino found by

Leon Lederman, Mel Schwartz, and Jack Steinberger, scientists at CERN

(the European Organization for Nuclear Research). They did this by firing

a GeV proton beam through a target thus producing pions, muons, and

muon neutrinos.

The existence of the third flavor of neutrino, the tau neutrino, was

first inferred in 1978 with the discovery of the Tau particle at the Stanford

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Linear Accelerator Center. They realized that the Tau particle was just a

heavier version of the electron and muon and therefore should have a

corresponding neutrino as well. However the tau neutrino evaded detection

for many years. First the Tau particle only lasts for about 300 fs

(femtoseconds — 10°'°s), making them difficult to track and therefore

making it difficult to track their corresponding neutrino. Second, tau

neutrinos are incredibly rare. However, in 2000 the scientists at CERN on

the DONUT detector were finally able observe a tau neutrino.

The solution to the solar neutrino problem finally came with the

discovery that neutrinos actually oscillate between three different

“flavors” after being emitted from the Sun as electron neutrinos. Therefore

they were not detecting all of the neutrinos because some had changed into

the two other flavors: muon and tau neutrinos that were not detectable with

their detector.

There are three types (flavors) of neutrinos: electron neutrino (ve),

muon neutrino (vu), and tau neutrino (vz). Neutrinos are nearly massless

and have no electric charge; therefore, they are often called ghost particles.

Unlike other particles, they only interact via the weak nuclear force. Since

the weak nuclear force only acts over very short ranges, neutrinos can pass

through massive objects without interacting with them.

Neutrinos are created in nuclear reactions — at power plants, in the

center of the Sun, and amid even more extreme events — when protons

accelerate, collide and then shatter in a shower of energetic particles.

Figure 2 illustrates the neutrino.

Neutrinos are so small that they seldom bump into atoms so

humans cannot feel them. They do not emit light, so our eyes cannot see

them. Yet these very qualities make them invaluable for conveying

information across time and space. Light can be blocked and gravitational

waves can be bent, but neutrinos are unscathed as they travel from the most

violent events in the universe straight into a detector at the bottom of the

Earth.

On the extremely rare occasions that neutrinos collide with other

matter they generate their corresponding charged particles. Many neutrino

detectors work by looking for the flash of light emitted by these charged

particles as they move through water or ice.

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What are neutrinos and how do we detect them?

Neutrinos are almost massless particles with a neutral charge that rarely

interact with other matter. They only do so via two forces:

| ae | Gravitational force Weak force

Gravity increases with Responsible for radioactive

mass. It is weak at decay. Limited to very

subatomic levels. short distances.

z Electron Because of these two forces,

neutrinos can “slip” through matter

without interacting, hence the

Nucleus O nickname “ghost particle.”

hg a

C <x |

. When a neutrino does bump into

& matter, it creates a charged particle.

Scientists observe these charged

Proton Neutron particles to detect neutrinos.

Note: Not drawn to scale.

Source: HyperPhysics/Georgia State University SHELLY TAN/THE WASHINGTON POST

Figure 2 — illustrates the neutrino and its interactions

Since the 1950s, when neutrinos were detected for the first time,

astronomers have observed low-energy versions of these ghostly particles

coming from the Sun and from the 1987 supernova in a nearby galaxy.

Maps of neutrinos emanating from the surface of the Earth have even been

used to identify the sites of nuclear reactors.

Move Outward into Space

As opposed to neutrinos, cosmic rays are extremely energetic

charged protons and atomic nuclei moving through space at almost the

speed of light. They're considered one of the threats to humans on a

potential mission to Mars: During the months-long journey through space,

cosmic rays would damage the cells of astronauts and could cause

radiation sickness.

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As early as the 1780s French physicist Charles-Augustin de

Coulomb noticed that charged particles were neutralizing the electric

charge of some of his experiments. In 1912 Austrian scientist Victor Hess

first demonstrated that these particles were arriving from space. He used a

hot-air balloon to take a detector high in the sky, where he soon observed

nearly three times as much ionizing radiation as at ground level. This

indicated that the mysterious particles were coming from above.

We now know that cosmic rays consist of different subatomic

particles: negatively charged electrons and positively charged protons and

atomic nuclei. Some cosmic rays have energies that far surpass what we

can achieve even in our largest particle accelerators. Very few phenomena

in the universe can accelerate particles to these speeds, which simply adds

to the phenomenon’s mystery. Where could they come from?

Quintillions of cosmic rays bombard Earth from space every

second. But it is nearly impossible to trace the paths of these atomic

fragments back to their sources. Most of them smash into atoms in the

upper atmosphere, creating a cascade of secondary particles that rain down

to the surface from different directions. What's more, most cosmic rays

carry an electric charge, which means their path changes every time they

encounter a magnetic field. And space is replete with magnetic fields, from

our own planet's relatively weak magnetosphere to powerful magnetic

vortices generated by magnetic stars.

Then on July 12 2018 it all changed. An international team of more

than 1,000 scientists announced they had tracked an associated particle

back to its origin, revealing for the first time one source of cosmic rays.

When the Sun was young and the Earth was barely formed, a

gigantic black hole in a distant, brilliant galaxy spewed out a powerful jet

of radiation. That jet contained neutrinos. Four billion years later, at

Earth’s South Pole, 5,160 sensors buried more than a mile beneath the ice

detected a single ghostly neutrino as it interacted with an atom. Scientists

then traced the particle back to the galaxy that created it.

This is multi-messenger astronomy at its best. The limits of

cosmic-ray detection had shifted the attention of astronomers toward other

sources of information. The discovery announced on July 12 is a triumph

of multi-messenger astronomy, in which scientists used multiple types of

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signals — in this case, electromagnetic waves and neutrinos — to probe

cosmological questions impossible to answer the old-fashioned (one-

message) way. By observing events in both light and neutrinos,

astronomers opened up a new type of multi-messenger astronomy. This

can tell us more about how distant galaxies form and evolve, and probe

some of the processes taking place in things like supermassive black holes.

IceCube Collaboration

It was just this detection scientists were dreaming of when the

National Science Foundation began building the $279 million IceCube

Neutrino Observatory in 2005. Working during the South Pole summer,

when the Sun never sets and temperatures hover at a negative 60 degrees

Fahrenheit, scientists and engineers melted dozens of mile-deep holes in

the ice and dropped strings of spherical sensors into them. (Neutrino

detectors are typically buried or submerged to filter out other cosmic

signals that would obscure the tiny particles.)

The National Science Foundation provided the primary funding for

the IceCube Neutrino Observatory. The University of Wisconsin—Madison

is the lead institution, responsible for the maintenance and operations of

the detector. Figure 3 shows the above ground IceCube. Approximately

300 astronomers from 49 institutions in 12 countries make up the IceCube

Collaboration.

REE OTT ENG ERP gs ahaa BPEL eas Sor

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Figure 3 — the above ground IceCube

The result was a grid array of sensors spread across a cubic

kilometer of glacier and capable of catching a ghost. The sensors record

the energy level and direction of the flash of light emitted by the charged

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particle created when a neutrino crashes into other matter. From that

information scientists can extrapolate the energy level of the neutrino and

where it came from. Figure 4 illustrates the IceCube Observatory.

The IceCube observatory uses thousands of light

sensors to detect neutrinos

The observatory encompasses one cubic kilometer of ice deep below

Antarctica’s surface.

86 “strings” set into ice, 125 meters apart

= omen ES

60 light sensors on

each string, each

17 meters apart

2450 m

Antarctic bedrock

The charged particle created in a neutrino

interaction emits light. The light sensors

os record the pattern and amount of light,

Lj tracking the particle’s direction and energy.

* @@ee@ee54e -

eeeeeee

Colored dots indicate that the sensors have

detected light (red where light was first

a detected, green where it was last measured).

Direction particle The larger the dot, the more light detected.

traveled

Note: Not drawn to scale.

Source: IceCube Collaboration/NSF SHELLY TAN/THE WASHINGTON POST

Figure 4 — the IceCube Observatory

Summer 2018

95)

Figure 5 illustrates how muon neutrinos can arrive at the IceCube

detector via different paths through the Earth. Neutrinos with higher

energies and with incoming directions closer to the North Pole are more

likely to interact with matter on their way through Earth.

Figure 5 How v, arrives at the detector

Encompassing a cubic kilometer of ice, IceCube searches for the

ghostly neutrinos. The neutrino observatory, which also includes the

surface array IceTop and the dense infill array DeepCore, was designed as

a multipurpose experiment. IceCube collaborators address several big

questions in astronomy, like the nature of dark matter and the properties

of the neutrino itself. IceCube also observes cosmic rays that interact with

the Earth’s atmosphere,

High-energy neutrinos, generated in extreme environments where

protons are accelerated to astonishing speeds, have been challenging to pin

down". Research suggests whatever process accelerates protons to such

speeds also generates high-energy neutrinos. To be detected, a neutrino

had to form long ago in a far-away cataclysm, travel un-diverted across

intergalactic space, fly through our Galaxy, enter our solar system, sail on

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to Earth, and then happen to interact with a particle in the ice below the

South Pole.

In a process that seems just as improbable, in the time since the

neutrino left its source four billion years ago, life on Earth had to arise,

expand, and evolve to the point that a few enterprising astronomers were

willing to go to the extreme effort of detecting it.

Since the observatory was completed in 2010, IceCube scientists

have detected dozens of high-energy neutrinos coming from outside the

solar system. But they were never able to connect those particles with a

source that could be observed by conventional telescopes.

So if IceCube could figure out where neutrinos were coming from

— a task made simpler by the fact that neutrinos are such dependable

messengers — they would know the source of cosmic rays as well.

“Neutrinos are the smoking gun,” Chad Finley, the coordinator of

the effort, said.”

The Detection

On September 22 2017 the IceCube observatory at the South Pole

detected an incoming high-energy neutrino. This detector has a real-time

alert system, and broadcast the coordinates of the detection to astronomers

around the world just 43 seconds after its discovery.

IceCube had seen the signature of a muon neutrino coming from

just above the right shoulder of the constellation Orion in the night sky.

Figure 6 shows the signal’s arrival at IceCube.

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* see sever

3 ,

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Figure 6 — the neutrino arrival at IceCube — traveling from right to left the light path is

indicated by the color changes.

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Swiftly, scores of scientists pointed their telescopes in that

direction, staring at the right region of the universe in every wavelength of

the electromagnetic spectrum. Astronomers using NASA’s Fermi space

telescope saw a burst of gamma rays coming from the presumed source.

Gamma rays are associated with the particle acceleration that produces

both neutrinos and cosmic rays.

Other space and ground based observatories saw flares of x-rays,

radio waves, and visible light. About 20 observatories responded to the

alert, and trained their views on the sky to work out where it was coming

from. Signals from gamma rays to radio waves across the entire

electromagnetic spectrum (the shorthand is SED, a spectral energy

distribution) revealed that the neutrino came from a spinning supermassive

black hole at the center of a giant elliptical galaxy some four billion light-

years away.

What they found was a blazing source, energetically flaring and

sending out gamma rays. And, as luck would have it, it also sent neutrinos

in our direction, and we were able to detect one.

It just so happens that one of the jets of high-energy particles

shooting away from the supermassive black hole points directly toward

Earth. a lucky accident. Astronomers call these objects blazars, and

although they are not the most powerful phenomena in the universe, they

certainly have the energy to accelerate a proton to the speeds seen in

cosmic rays. Blazars are elliptical galaxies with a supermassive black hole

in the center. Supermassive black holes are accompanied by twin jets of

relativistic high energy particles streaming outward. In the case of a blazar

the jet points toward the Earth. Figure 7 is an artist’s conception of a blazar.

Figure 7 — an artist’s conception of a blazar

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The blazar was given the name TXS 0506+056'" — the first

identified source of a high-energy neutrino, and a possible answer to the

century-old cosmic ray mystery.

Crosschecking the observation, the IceCube team went back

through their old data to examine whether any other neutrinos had come

from the same direction. They did not expect to find anything. So they

were shocked to discover that IceCube had recorded more than a dozen

neutrino events from what they now knew was the same blazar between

late 2014 and early 2015.

The announcement came in the journal Science. The abstract from

that announcement is:

“A high-energy neutrino event detected by IceCube on 22

September 2017 was coincident in direction and time with a gamma-ray

flare from the blazar TXS 0506+056. Prompted by this association, we

investigated 9.5 years of IceCube neutrino observations to search for

excess emission at the position of the blazar. We found an excess of high-

energy neutrino events, with respect to atmospheric backgrounds, at that

position between September 2014 and March 2015. Allowing for time-

variable flux, this constitutes 3.50 evidence for neutrino emission from the

direction of TXS 0506+056, independent of and prior to the 2017 flaring

episode. This suggests that blazars are identifiable sources of the high-

energy astrophysical neutrino flux.”

Until this discovery there had been a general consensus that blazars

might be sources of cosmic rays but there was no evidence. The discovery

of the neutrinos showed one blazar that produces high energy cosmic rays.

Combining information from different messengers gave a new glimpse

into the cosmos. Figure 8 is an artist’s conception of how a blazar makes

neutrinos.

As opposed to cosmic rays which are tossed about by intervening

magnetic fields, neutrinos from this blazar traveled in almost a straight line

directly towards Earth, allowing their origin to be teased out of the data.

Summer 2018

Figure 8 — a blazar accelerates protons (the yellow p) to the energy levels of cosmic

rays, initiating a complex quantum cascade that also releases gamma rays (magenta) and

neutrinos (blue), which follow straight paths through space. The coupled detection of

these two particles enabled astronomers to identify the blazar as a source of cosmic rays.

Credit: IceCube/NASA

A Beautiful Messenger

“It’s crazy,” said Chad Finley, at Stockholm University who spent

10 years coordinating the effort to pinpoint neutrinos’ origins for the

IceCube team. “These are particles that seldom interact with anything.

That has to be the unluckiest neutrino ever.” He and his colleagues are

some pretty lucky humans.”!

Combined with gravitational wave detection and traditional light

astronomy, the observation of a neutrino from a known source gives

astronomers three ways to observe the cosmos, truly an era of multi-

messenger astronomy. Since gravitational waves are often described as the

way we “hear” the universe, and light is how we “see” it, perhaps neutrinos

would be how we “smell” it.

Of all these “senses,” neutrinos are in some ways the most reliable.

High-energy light from distant sources rarely makes it to Earth, because

photons are so reactive they get lost along the way. Neutrinos, on the other

hand, will travel in a straight line right from their origin point to a detector.

It is an absolutely beautiful messenger.

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Back to the Neutrino

The ghost in the neutrino means they can be used to probe celestial

objects that light cannot penetrate. Astronomers using regular telescopes

cannot see beneath the surface of the Sun, but 30 years of observations of

the low-energy neutrinos that emanate from our star's center have allowed

astronomers to peer into its core. By looking at their energy levels,

astronomers could understand the fusion process that creates the neutrinos

and generates the Sun’s energy. It takes 100,000 years for energy at the

center of the Sun to make it to the surface, which means the Sun is going

to keep working for at least 100,000 years.

The neutrinos detected by IceCube are millions of times more

energetic than those coming from the Sun, but they offer the same kinds

of insights into the intense environments from which the particles emanate.

The telescopes looking at TXS 0506+056 could only capture what

happened on the surface of the blazar; the neutrinos carry signatures of the

processes at its very center.

It is in these extreme settings that the laws of nature are stretched

to their limits. What neutrinos reveal about the acceleration of charged

particles and the behavior of black holes could help astronomers refine the

rules of physics — or rethink them. There are even more energetic

neutrinos out there — ones that make the powerful IceCube particles look

practically wimpy.

It is not a trivial question to ask how much mass a neutrino has.

However they are still a billion times smaller than any other type of known

subatomic particle. Yet there so many of them that their combined masses

could give them cosmological significance. We badly need to know what

that mass is in order to figure out how they might affect the future of the

universe.

For example, if neutrinos prove to be on the heavy side of current

estimates, then their combined gravitation pull would affect the expansion

of the cosmos and slow it down. However, if their mass is on the light side,

neutrinos, despite their cosmological ubiquity, will be unable to act as any

kind of meaningful brake to the universe’s expansion.

All other particles get their mass by attaching themselves to Higgs

bosons, but the neutrino must do it by a very different route. So there is

Summer 2018

some other method involved and uncovering that method would be a real

prize.

It is for these reasons that scientists have struggled, over the

decades, to find the exact mass of the neutrino. The first efforts, made after

the WWII, placed an upper limit on its mass at around 500 electron volts

(eV). This figure is about 1/500th of the mass of the electron, itself a

relatively tiny particle. (the masses of all subatomic particles are measured

in electron volts, which can also be used as a unit of mass because energy

and mass are convertible concepts according to Einstein’s E = mc?

equation.)

The 2015 Nobel Prize in physics has been awarded to Takaaki

Kajita and Arthur McDonald for discovering that the elusive subatomic

particles called neutrinos weigh something more than nothing.

With two separate detectors built deep underground, one a

kilometer beneath a mountain in Gifu prefecture, and the other two km

down an old nickel mine in Ontario, the two scientists discovered that

neutrinos can flip from one form to another as they hurtle through space —

a chameleon-like behavior that proves they have mass.

On hearing he had won, Kajita said it was “unbelievable”. At a

press conference in Tokyo, he added: “I want to thank the neutrinos, of

course. And since neutrinos are created by cosmic rays, I want to thank

them, too.””!

Neutrinos are among the most abundant particles in the universe

and thousands of billions of them pass through each of us every second of

the day without us noticing. Many were forged in the big bang, but others

are created constantly through radioactive decay inside the Earth, by

exploding stars, and in nuclear processes that power the Sun.

Kajita and McDonald’s work solved the puzzling observation that,

compared with theoretical calculations of the number of neutrinos

expected to be bombarding the Earth from the Sun, up to two-thirds were

apparently not arriving.

In 1998, Kajita’s team discovered that neutrinos created when

cosmic rays slam into the Earth’s atmosphere changed flavors on their way

to the Super-Kamiokande detector under Mount Kamioka in Japan. Then,

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on the other side of the world in 2001, McDonald’s team saw that neutrinos

from the Sun, detected by the Sudbury Neutrino Observatory in Canada,

also switched identities.

The finding implied that neutrinos must have mass, a discovery that

meant the so-called standard model of physics could not be complete in its

explanation of the fundamental building blocks of the universe.

Current measurements, carried out in Mainz, Germany and Troitsk

in Russia, have pushed this figure further and further downwards with the

result that the upper limit for the combined neutrino mass is now set <

0.120 eV/c”, about two billionth the mass of the lightest atom.

Scientists now know that the neutrino mass is more than a million

times less than that of the electron. But because the particles are so

abundant, the combined weight of neutrinos is estimated to be roughly

equal to the combined weight of all the visible stars in the universe.

The humble neutrino has come into its own.

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Neutrino Multi-messenger

23 Sep 2017; toe

20:54:30 (UT) a very-highenergy

neutrino is

coming form there!

Hi Fermi-san!

Can you (altitude $50km)

see anything

in that

direction? P| \) rT J

Gamma-rays are Ay gamma-ray (photon)

getting stronger ~~ 2

from there! @

Pre a

Observatories!

Look that direction!

A neutrino and

gamma-rays may come

from a same point source!

but my expertise is

gamma-rays with

much higher energy

than Fermi-san

so | am not sure

@Canary islands, Spai , | can see it...

Really high

energy gamma-rays

are coming

from there!

It must be

the same source

with what

IceCube-san saw!

Chiggstan.com

http://higgstan.com/icecube | 70922a/

' https://icecube.wisc.edu/ accessed July 14 2018

' The solar neutrinos are low energy neutrinos

i https://www. washingtonpost.com/news/speaking-of-science/wp/2018/07/12/in-a-

cosmic-first-scientists-detect-ghostly-neutrinos-from-a-distant-

galaxy/?utm_term=.0105lc8cbc81 accessed 14 July 2018

'v The numbers identify the coordinates of the object

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’ Neutrino emission from the direction of the blazar TXS 0506+056 prior to the

IceCube-170922A alert, Science 12 July, 2018

www.sciencemag.org/egi/content/full/science.aat2890/DC |

“ https://www.washingtonpost.com/new s/speaking-of-science/wp/2018/07/1 2/in-a-

cosmic-first-scientists-detect-ghostly-neutrinos-from-a-distant-

galaxy/?utm_term=.0105lc8cbe81 accessed 14 July 2018

“ https://en.wikipedia.org/wiki/Takaaki_Kajita accessed July 13 2018

Bio

Sethanne Howard is an astronomer retired from the US Naval Observatory.

She has worked at the National Science Foundation and NASA and is a

Fellow of the Washington Academy of Sciences..

Summer 2018

Washington Academy of Sciences

Message from Outgoing 2017-2018 President

When I was installed as the President of the Washington Academy of

Sciences for the 2017-2018 year, I listed five goals to work for over the

year. I can state that WAS made progress on some of the goals. For other

goals there is work to be done. We need to continue our efforts to bring in

new members from different scientific disciplines. We need to intensify our

efforts to reach out to all of our current members to encourage them to

participate in the work of the Academy. The members of the Academy

represent a World Bank of scientific talent that needs to be explored for our

work.

My work over the past year has been supported by the incredible talents of

our current officers and board members. The efforts of Terry Longstreth,

Ron Hietala and Sethanne Howard to keep the Washington Academy of

Sciences operating are legendary.

Tonight the Washington Academy of Sciences stands proud as the talents

of outstanding scientists in the Washington area are recognized. The

Academy welcomes you. We look forward to your future work and your

participation in the work of the Academy as new members of our

organization.

I now stand aside to take up the position of Past President. I welcome the

new President, Dr. Mina Izadjoo, and the President Elect, Dr. Judy Staveley.

Dr. Izadjoo and Dr. Staveley are talented scientists who will lead the

Academy’s work in the coming year putting forth innovative and modern

ideas for the scientific work of the Academy.

We thank you all for joining us the evening. We welcome our outstanding

awardees as new members and look forward to your participation in our

work in the coming year.

Sue Cross

Summer 2018

Message from the Incoming President

Dear Members and Affiliates,

It is a great pleasure and honor to be elected as president of the Washington

Academy of Sciences. I am humbled that you have placed your faith and

trust in me.

Science is a dynamic and creative journey and as scientists it is upon us to

promote science in our community. Today, the world is much different since

the inception of the Academy in 1898. However, Washington Academy of

Sciences continues with its original mission and strives to make the

Academy the voice of today’s science and scientists.

We have come a long way since the inception of the Academy by a group

of scientists in the Washington area from eight scientific societies. The

Academy was formed as an umbrella organization to promote collaboration

among various scientific disciplines. Today, more than a century later with

nearly 60 affiliated organizations, the Academy continues to effectively

pursue its goal which is to stimulate scientific interest and promote science

through collaboration, membership, and publication.

The Academy with its rich history brings together the local scientific

societies and scientists. | am committed to strengthen our ties and establish

working relationships with other institutions in the community. Our

members have a diverse scientific background which is an empowering tool

for advancing the scientific objectives of the Academy. This year the

Academy will hold various functions including fund raising and networking

events. I invite and encourage you to be involved.

Please let me know how I can serve you better, and I look forward to hearing

from you.

Respectfully,

Mina Izadjoo, Ph.D.

Washington Academy of Sciences

2018 Awardees

Summer 2018

\eS)

Washington Academy of Sciences

Mark D. Stiles — Excellence in Research in Physical Sciences

Summer 2018

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Vijayanand C. Kowtha — Krupsaw Award

Washington Academy of Sciences

William C. Regli - Excellence in Research in Computer Science

Summer 2018

Washington Academy of Sciences

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Summer 2018

o>)

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ily

Instructions to Authors

Deadlines for quarterly submissions are:

Spring — February | Fall — August |

Summer — May 1 Winter — November |

Draft Manuscripts using a word processing program (such as

MSWord), not PDF. We do not accept PDF manuscripts.

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reduce the number of words by 500 for each graphic.

Include an abstract of 150-200 words.

Include a two to three sentence bio of the authors.

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Submit papers as email attachments to the editor or to

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Include the author’s name, affiliation, and contact information —

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may also be noted. It is not required.

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Manuscripts can be accepted by any of the Board of Discipline Editors.

Washington Academy of Sciences

Affiliated Institutions

National Institute for Standards & Technology (NIST)

Meadowlark Botanical Gardens

The John W. Kluge Center of the Library of Congress

Potomac Overlook Regional Park

Koshland Science Museum

American Registry of Pathology

Living Oceans Foundation

National Rural Electric Cooperative Association (NRECA)

Summer 2018

Delegates to the Washington Academy of Sciences

Representing Affiliated Scientific Societies

Acoustical Society of America

American/International Association of Dental Research

American Assoc. of Physics Teachers, Chesapeake

Section

American Astronomical Society

American Fisheries Society

American Institute of Aeronautics and Astronautics

American Institute of Mining, Metallurgy & Exploration

American Meteorological Society

American Nuclear Society

American Phytopathological Society

American Society for Cybernetics

American Society for Microbiology

American Society of Civil Engineers

American Society of Mechanical Engineers

American Society of Plant Physiology

Anthropological Society of Washington

ASM International

Association for Women in Science

Association for Computing Machinery

Association for Science, Technology, and Innovation

Association of Information Technology Professionals

Biological Society of Washington

Botanical Society of Washington

Capital Area Food Protection Association

Chemical Society of Washington

District of Columbia Institute of Chemists

District of Columbia Psychology Association

Eastern Sociological Society

Electrochemical Society

Entomological Society of Washington

Geological Society of Washington

Historical Society of Washington DC

Human Factors and Ergonomics Society

(continued on next page)

Paul Arveson

J. Terrell Hoffeld

Frank R. Haig, S. J.

Sethanne Howard

Lee Benaka

David W. Brandt

E. Lee Bray

Vacant

Charles Martin

Vacant

Stuart Umpleby

Vacant

Daniel J. Vavrick

Mark Holland

Vacant

Toni Marechaux

Jodi Wesemann

Vacant

F. Douglas

Witherspoon

Vacant

Chris Puttock

Keith Lempel

Vacant

Ronald W.

Mandersheid

Vacant

Jurate Landwehr

Vacant

Gerald Krueger

Washington Academy of Sciences

Delegates to the Washington Academy of Sciences

Representing Affiliated Scientific Societies

(continued from previous page)

Institute of Electrical and Electronics Engineers, Washington

Section

Institute of Food Technologies, Washington DC Section

Institute of Industrial Engineers, National Capital Chapter

International Association for Dental Research, American

Section

International Society for the Systems Sciences

International Society of Automation, Baltimore Washington

Section

Instrument Society of America

Marine Technology Society

Maryland Native Plant Society

Mathematical Association of America, Maryland-District of

Columbia-Virginia Section

Medical Society of the District of Columbia

National Capital Area Skeptics

National Capital Astronomers

National Geographic Society

Optical Society of America, National Capital Section

Pest Science Society of America

Philosophical Society of Washington

Society for Experimental Biology and Medicine

Society of American Foresters, National Capital Society

Society of American Military Engineers, Washington DC

Post

Society of Manufacturing Engineers, Washington DC

Chapter

Society of Mining, Metallurgy, and Exploration, Inc.,

Washington DC Section

Soil and Water Conservation Society, National Capital

Chapter

Technology Transfer Society, Washington Area Chapter

Virginia Native Plant Society, Potowmack Chapter

Washington DC Chapter of the Institute for Operations

Research and the Management Sciences (WINFORMS)

Washington Evolutionary Systems Society

Washington History of Science Club

Washington Paint Technology Group

Washington Society of Engineers

Washington Society for the History of Medicine

Washington Statistical Society

World Future Society, National Capital Region Chapter

Richard Hill

Taylor Wallace

Neal F. Schmeidler

Christopher Fox

Vacant

Richard

Sommerfield

Hank Hegner

Jake Sobin

Vacant

John Hamman

Julian Craig

Vacant

Jay H. Miller

Vacant

Jim Heaney

Vacant

Larry S. Millstein

Vacant

Marilyn Buford

Vacant

E. Lee Bray

Erika Larsen

Richard Leshuk

Alan Ford

Meagan Pitluck-

Schmitt

Vacant

Albert G. Gluckman

Vacant

Alvin Reiner

Alain Touwaide

Michael P. Cohen

Jim Honig