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Curriculum Vitae
PERSONAL:
Name : Tapasi Ghosh
Contact Address : Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo,
Puerto Rico,
PR 00612. USA, Tel: (787)-878-2612, Fax: (787)-878-1861, E-mail: tghosh@naic.edu
Date and Place of Birth : 13 November 1959, Calcutta, India.
Nationality : Indian
Marital Status : Married, with a seven year old daughter.
Fluency in Languages other than English: My mother tongue is Bengali
(one of the 17 oфcial languages in India) although, I have been using English for
more than 25 years now and most of my formal education has been in English. In
addition, I also have limited command of Spanish and a brief exposure to Dutch.
EDUCATION:
B.Sc. Physics (Hons) Lady Brabourne College, Calcutta, India. 1979
M.Sc. Physics University College of Science, Calcutta, India. 1981
Post M.Sc Associate Saha Inst. of Nuclear Phys., Calcutta, India. 1982-83
(Bio-Physics)
Ph.D (Astronomy) Indian Inst. of Science, Bangalore, India. 1990
Thesis Topic: \Low-Frequency Variability of
Compact Extragalactic Radio Sources"
EMPLOYMENT:
Dec 1990 { Nov 1992, Post-doctoral Fellow, Netherlands Foundation for
Research in Astronomy. Dwingeloo, The Netherlands.
Dec 1992 { Present, Research Associate at the Arecibo Observatory. Re-
sponsibilities include visiting observers' support, absentee VLBI observing
and coordinating VLBI related work help in calibrating and documenting a
few of the radio receivers at the observatory, supervising summer students,
and carrying astronomical research of personal interest.
RESEARCH INTERESTS:

(A) CURRENT PROJECTS
(1) The Turbulent Ionized Interstellar Medium:
The properties of the ionised component of the interstellar medium can be in-
ferred from its eects on radio-wave propagation. The scattering of radio waves
by electron-density inhomogeneities in the ISM produces a number of observables
such as angular broadening and low-frequency variability of compact sources, and
the intensity uctuations and temporal broadening of pulsar signals. The scat-
tering medium is characterised by the power spectrum of its electron-density
uctuations, generally believed to have a power-law form, although details of the
nature of the power-law is still under active investigation. As yet, the galactic
distribution of this medium is not fully characterised. Attempts to interpret
the distribution of interstellar turbulence via both scatter broadening and low-
frequency variability of extragalactic sources suggests that it possesses spiral
structure, similar to other Population-I components. To establish whether this
is so, Chris Salter, Bill Junor, Jose Salgado, P.K. Manoharan and myself have un-
dertaken a study of the scatter broadening of low-latitude compact extragalactic
sources lying within 30 ф l 75 ф . In this region, lines-of-sight pass progressively
from the Sagittarius-arm tangent point, through the local inter-arm direction
and into the Cygnus-Orion arm. 32 compact extragalactic at-spectrum sources
have been observed at 18, 49 and 90 cm using the VLBA. Supplementary data
have also been taken using the MERLIN array in the UK and the Ooty Radio
Telescope in India.
The results so far indicate that the scatter-broadening is at least a magnitude
larger for lines-of-sight passing through spiral arms compared to those through
the inter-arm regions. Detailed comparison of the scatter-broadened sizes with
predictions from various models has been done. This study formed the major
part of the Ph.D. thesis of Jose Francisco Salgado of the University of Michigan
(April 2000).
(2) Seyfert Galaxies:
The Seyfert phenomenon occurs most commonly in early-type spiral galaxies
and is usually accepted to be the result of accretion of gas on to a super massive
Black Hole at the center of the galaxy. However, the details of the accretion
process of the neutral gas from the outer disk region into the center is far from
clear. The eects of the orientation of the galaxy on observations are also a
major contributing factor in our understanding of such objects. It has been
demonstrated by Antonucci and Miller, that the apparent dierences between
Seyfert 1 (broad-emission line AGNs) and Seyfert 2 (narrow-line AGNs) galaxies
are due to whether the line-of-sight avoids or passes through a neutral, dusty,
(optically) obscuring torus.
However, the radio-continuum properties of Seyfert 1 and 2s are far from being

in simple agreement with the above scenario. Assuming that the synchrotron
radio emission from most Seyfert galaxies originates from two oppositely directed
jets, the unied scheme predicts that the jets in Type 1 objects should, on the
average, be fore-shortened relative to those in Type 2s, and relativistic Doppler
boosting would lead to the detection of brighter radio sources in Type 1 objects
with one-sided or asymmetric jets. To date, various radio surveys of Seyferts
have produced con icting results. High resolution maps of Seyferts galaxies
by various authors, including EVN & MERLIN maps made by M. Kukula, A.
Pedlar, R. Schilizzi and myself show cases where prominent jets are seen in both
Type 1 and Type 2 objects. In addition, very compact radio sources are seen
in Seyfert 2s where fore-shortening due to projection eects is expected to be
minimal. The emerging picture suggests that in Seyfert galaxies the radio jets
are either short-lived compared to the AGN, thereby populating a sample with
jets at various stages of development, or the production and propagation of jets
could be highly in uenced by the gas-rich environment of the galaxy (compared
to quasars and radio galaxies likely to be hosted mostly by giant ellipticals).
The second possibility has gained more observational evidence in recent years
as high-resolution mapping of HI-absorptions in these objects becomes available
demonstrating interactions between synchrotron knots and cold, neutral gas very
close to the central obscuring torus.
If it is just orientation that determines whether a Seyfert AGN is seen to be of
Type 1 or 2, then the average neutral-hydrogen content of the two classes of ob-
jects should show no signicant dierence. However, in addition to orientations,
if the gas dynamics in the inner region of these galaxies have some contribut-
ing eect in triggering either dierent AGN or synchrotron-radio properties, the
signature of that may be found in the neutral-hydrogen spectra of these galax-
ies. To investigate this, Jo Ann Eder, Chris Salter and I have undertaken a
HI survey of a large, unbiased sample of Seyfert 1 and 2 galaxies. About 100
hours of spectral-line observing have recently been completed at Arecibo. The
results show no signicant dierence in (1) line-width and (2) neutral hydrogen
content between the two Seyfert types. However, compared to normal early-type
galaxies (E0s), the Seyferts in our sample contain an order of magnitude higher
amount of neutral hydrogen. Further, the ratio of integrated HI spectrum to
continuum ux density does not seem to be signicantly dierent for Seyfert 1
and 2s, although the rst of these is expected to be orientation independent and
the second orientation dependent.
(3) Ultra-luminous infra-red galaxies:
An important result which emerged from the IRAS mission was the recognition
of a class of optically-faint galaxies that are as luminous as quasars at far-infrared
(FIR) wavelengths. Such galaxies are extremely rich in molecular gas content,
possess values of optical-line ratios that imply the presence of strong non-thermal
ionising radiation, and are mostly found in interacting systems. To account for

their high FIR luminosities, these galaxies almost certainly need an additional
energy source, rather than being simply large and/or dusty galaxies. The obvious
suggestions for the origin of this additional energy have been, (1) star-burst
phenomena, (2) heavily-obscured active nuclei (AGN), and/or (3) merger, or
interaction, with other galaxies. For a sample of 20 such ultraluminous galaxies
with L 60 > 10 11:5
L we are measuring HI absorption/emission spectra using the
Arecibo Telescope. This will help throw light on the kinematics in the nuclear
regions of these galaxies.
(4) Host galaxies of quasars:
The host galaxies of quasars are diфcult to detect at most wavelengths as the line
and continuum radiation from the associated active nuclei swamps the emission
from the underlying galaxy. Despite this diфculty, optical \fuzz" showing stel-
lar spectra has been detected around nearby quasars using both ground-based
telescopes and the HST. In addition, near-infrared imaging has been quite suc-
cessful in detecting the host galaxies of Seyferts and nearby quasars. Recently,
these types of search have been extended to a redshift of z = 2:3. The picture
that is emerging suggests that at higher redshifts, radio-loud QSOs are hosted by
exceptionally luminous galaxies, while the majority of QSO hosts are too faint
to detect.
At radio wavelengths, searches for neutral hydrogen and molecular lines in QSO
spectra have been made since the rst detection of HI absorption towards 3C286
by Brown & Roberts in 1973. As quasar nuclei emit neither 21-cm HI line
radiation, nor molecular lines, their host galaxies can generally be observed as
easily in these transitions as if they contained no active nuclei at all. HI emission
has been detected in QSOs with redshift values up to z = 0:1; while at higher
redshifts little work has been done. HI absorption associated with a host galaxy
has been detected only for the BL Lac object, PKS 1413+135 at z=0.246, while
molecular gas and dust emission has recently been detected in a number of active
galaxies with redshifts up to 4.7. For a sample of 18 radio-loud quasars at
a redshift of about 2.3, we (Mike Davis, Chris Salter, Monique Aller and I) are
searching for HI absorption associated with their host galaxies using the upgraded
Arecibo Telescope in its observing band around 430 MHz. Radio Frequency
interference is signicant at this frequency and we have developed a successful
strategy to minimise its eects.
(4) Damped Lyman- Absorbers:
Much of what is known about neutral gas at high redshifts comes from the
study of Lyman- absorption lines observed in the spectra of distant quasars.
The highest HI column density systems, the so-called damped Lyman- (DLA)
systems, are of particular interest, because they are believed to be the precursors
of z = 0 galaxies.

The typical mass of DLA systems is currently controversial. Small sizes are pre-
ferred in hierarchical structure formation theories, while a popular model in the
observational literature assumes that DLAs are large, massive disks. Further,
from local 21cm emission line studies, it is expected that the absorption cross
section is dominated by the disks of spiral galaxies. On the other hand, galax-
ies associated with DLAs appear to cover all morphological types, and are not
conned to spirals alone. In collaboration with Drs. Jayaram Chengalur and
Nissim Kaneker of NCRA. TIFR (India) I am searching for HI emission from a
low z DLA system using the Arecibo Telescope . This would allow the estimation
of the total HI mass of the absorber, and, unlike optical studies, would also be
sensitive to the presence of a large gas rich but low optical surface brightness
disk.
(B) FUTURE RESEARCH-RELATED PLANS :
Extend the mapping and modeling of the galactic distribution of electron-
density uctuations to include all sky, and investigate the nature and the
orgin of such uctuations which covers an amazingly large range.
Detailed observational studies of the environment, host and cosmological
evolution of AGNs. This will involve high resolution as well as single-dish
continuum and spectral line (in HI and OH mega-maser and CO lines)
observations of dierent types of AGNs as function of redshifts.
A multi-frequency search for \extreme scattering events" in the ux densi-
ties of extragalactic sources seen through \disturbed" lines-of-sight in the
galactic plane. Daniel Altschuler, Jose Salgado and I found one such event
for a source B2050+366 at 430-MHz in a 14-year Arecibo low-frequency
monitoring programme which ran until the beginning of the Arecibo up-
grade. This is the rst such event to be observed below 1 GHz.
Search for intraday/intra-hour variability in ultra-compact extragalactic
radio sources.
Studies of Damped Lyman- Absorbers at radio wavelengths.
TEACHING-RELATED EXPERIENCE:
Along with Chris Salter, I have supervised the doctoral thesis of Jose Francisco
Salgado from the University of Michigan (April 2000).
I have supervised the following undergraduate summer students between 1993
and 2001 (NSF's REU Program). The name, aфliation and project title of each
student is listed below:

2001: SunMi Chung (Weslyan College), \ PKS1004+13: The Rosetta Stone
for BAL Quasars ?", Chris Salter and Daniel Altschuler are co-investigators
in this project.
1999: Dargan Frierson (North Carolina State University) \HI spectra of
Seyfert Galaxies and testing their unication scheme". Jo Ann Eder and
Chris Salter are co-investigators in this project.
1998: Monique Aller (Wellesley) \A search for high redshift hydrogen ab-
sorption in radio-loud quasars". This used both the 430-MHz line and Gre-
gorian feeds. The data analysis involved the development of various tech-
niques for RFI excision. Mike Davis and Chris Salter are co-investigators
in this project.
1998: Dale Kocevski (Univ. of Michigan) \The RFI environment as seen
by the Gregorian L-band receiver." With Jo Ann Eder and I, Dale analysed
drift-scan data taken on a total of 15 nights between November 1997 and
April 1998 and spanning the entire frequency range covered by the receiver,
1360 - 1685 MHz. The RMS and Average per channel over daily observing
periods were calculated, plotted and stored for reference in the Control
Room. Dale also listed the worst oenders and their occupancy rates (the
fraction of nights during which the RFI was present). This RFI information
has helped observers to plan their observing strategies.
1997: Francisco Acevedo (Embry-Riddle College, Florida), \Measurement
of the Electromagnetic and Radio Frequency Interference (EMI and RFI)
at key locations within the Observatory". This work produced a list of
equipment producing considerable RFI, which were subsequently shielded.
1996: Cesar Tavarez (Univ. of Mayaguez, Puerto Rico), \Analysis of Radio
Frequency monitoring data collected round the clock at Arecibo Observa-
tory". The results provide valuable percentage occupancy plots for various
spectrum users as functions of both frequency and time of the day.
1995: Evan Jones (SMSU, USA), \On the environmental triggering of radio
emission in Seyfert galaxies".
1994: Deepa Iyengar (Carleton College, USA), \VLBI imaging of the
scatter-broadening of compact extragalactic radio sources seen through the
plane of the Galaxy".
1993: Ben Oppenheimer (Columbia Univ, NY), Co-supervised with
Chris Salter on \Refractive interstellar scintillations of the pulsar, PSR
1933+16".
Lectured on \Radio Galaxies and Quasars" and \Radio Interferometry" to the
AO summer students between 1993 and 1998.

In addition, I helped Chris Salter and Jo Ann Eder with the planning, and
analysis of the joint summer-student observing project in 1998, "Single Epoch
Measurements of Broad-band Radio Continuum Spectra". This was the rst year
since 1993 that the telescope had been available for a summer-student observing
project.
SERVICE WORK AT ARECIBO OBSRVATORY:
VLBI related work:
{ I am a member of the Arecibo VLBI group, and am actively involved
in co-observing with the VSOP space antenna, HALCA, using a Cana-
dian S2 recorder system. Since the upgraded telescope returned to ob-
serving in mid 1997, there have been 30 Arecibo VLBI observing runs.
Jointly with Chris Salter, I have conducted all these observations and
subsequent calibration, system checks and tape handling. To date,
we have not had a failure to detect fringes that can be attributed to
problems at Arecibo.
{ In late 1996, Chris Salter and I prepared a proposal to the NSF Ma-
jor Research Instrumentation (MRI) Program for the purchase of a
broad-band VLBA-4 recorder and associated hardware for Arecibo.
We heard in September 1997 that the proposal had been successful,
and was to be fully funded (about US $ 500,000.00). The unit arrived
at AO in March 2001, and a successful test run with three other VLBA
stations was conducted in April. Details of the operations are being
worked out at present, and a particular component is being repaired
at the manufacturers'. The VLBA4 recorder will be put to full use as
soon as possible.
Spectrum Management and RFI protection related work: Un-
til April 2001, I have been responsible for coordinating the local activi-
ties of the Spectrum Management and RFI protection Group (SMARG)
at Arecibo. This required working with a 10-member group consist-
ing of engineers, software personnel, scientic sta and telescope oper-
ators to ensure that the radio-spectrum allocated to radio astronomy
is maintained interference free and protected at Arecibo. This entails
minimising emissions from on-site equipment, monitoring the wider ra-
dio environment, searching for sources of interference using a mobile
unit, and liaison work with local spectrum users and authorities in cases
of complaints. Details of the functions of this group can be found
at http://www.naic.edu/tghosh/smarg/index.html (this webpage
was developed by myself).
Arecibo Telescope Commissioning and Calibration :

{ Along with Chris Salter, I compiled a catalogue of continuum calibra-
tor sources containing about 1500 entries. The list has been exten-
sively used during the commissioning phase of the telescope and forms
the basis of all standard pointing procedures.
{ I have been responsible for dening and characterising the RFI envi-
ronment as seen by the assortment of receivers on the telescope.
{ Along with Jo Ann Eder and Chris Salter, I have measured and char-
acterised the telescope performance at 5 and 0.43 GHz.
Between March 1994 and February 2000, I have been the co-editor (along
with Jonathan Friedman) of the AO/NAIC Newsletter. This is published
three times per year. This work has involved me in planning, editing and
producing the Newsletter.
SOFTWARE and DATA REDUCTION EXPERIENCE :
Since 1983, I have been using Fortran as my basic programming language. I
have worked with PDP, Alliant, Vax/VMS, Unix and Solaris operating systems.
I am also familiar with a variety of word processing and desk-top publishing
software (both Windows and Apple-Macintosh based). I am quite conversant
with html-based web-page developments.
For Astronomical data reductions, I have used the following software packages:
The OSRT Calibration and Synthesis mapping package (a number of new
programmes were developed by myself in order to facilitate the particular
needs of the Ooty ux-density monitoring programme)
The Ooty Interplanetary Scintillation (IPS) data reduction package
The NRAO AIPS image processing system
The Caltech VLBI package
DWARF/NEWSTAR, the Westerbork Astronomical Reduction Facility.
OLAF, the MERLIN data reduction package
ANALYZ, the Arecibo Observatory astronomical data reduction package
The NOAO IRAF package
Optical identication of radio sources from Palomar Observatory Sky Sur-
vey (POSS) prints using ne-scale distance measuring machines at Ooty
and Dwingeloo, and also from the digitised CDs of the POSS.
IDL

CONTACT PERSONS FOR RECOMMENDATIONS:
1. Dr. Daniel Altschuler, Arecibo Observatory, HC3 Box 53995, Arecibo,
PR 00612, USA. Tel: +1 787 878 2612, Fax: +1 787 878 2612, E-
mail:daniel@naic.edu
2. Dr. Bill Junor, Institute for Astrophysics, Department of Physics and As-
tronomy, 800 Yale Boulevard, NE, University of New Mexico, Albuquerque,
NM 87131, USA. Tel: +1 505 277 2616, Fax: +1 505 277 1520, E-mail:
bjunor@astro.phys.unm.edu
3. Dr. D.J. Saikia, Department of Physics, Queen's University at Kingston, 99
University Avenue, Kingston, Ontario, Canada, K7L 3N6. Tel: (613) 533-2707,
Fax: (613) 533-6463, E-mail: djs@lola.phy.queensu.ca. On Leave from NCRA,
TIFR, India.
PUBLICATIONS:
1. Gopal-Krishna, Ghosh, T. and Saripalli, L.
\CERCO" - A Compendium of Extragalactic Radio sources, Catalogues and
Observations,
1985, circulated from Tata Institute of Fundamental Research, India.
2. Gopal-Krishna, Steppe, H., Ghosh, T. and Saripalli, L.
A statistical analysis of the radio properties of a large sample of 374 optically
selected quasars.
1986, IAU Symp. 119, p. 111.
3. Ghosh, T. and Rao, A. P.
Observations of low frequency variables at Ooty,
1987, NRAO Workshop No. 20: Large-scale Surveys of the Sky, p.43.
4. Ghosh, T. and Gopal-Krishna.
A multifrequency study of radio intensity variations for active galactic nuclei of
dierent optical classes.
1990, A&A 230, 297.
5. Saikia, D. J., Salter, C. J., Banhatti, D.G., Ghosh, T., Gothoskar, P. and
Manoharan, P.K.
The Ooty Summer Training Programme 1990,
1991, Bull. Astr. Soc. India., 19, 109.
6. Ghosh, T. and Rao, A. P.
The Galactic latitude dependence of Low Frequency Variability of extragalactic
radio sources.
1992, A&A 264, 203.

7. Kukula, M. J., Ghosh, T., Pedlar, A., Schilizzi, R. T., Miley, G. K., deBruyn,
A. G., Saikia, D.J.
High resolution radio observations of Markarian 3.
1993, MNRAS 264, 893.
8. Oppenheimer, B.R., Salter, C.J., Biggs, J., Foster, R., Ghosh, T.
Monitoring the interstellar scintillations of PSR 1933+16 : Eight epochs from
Jan 1992 to May 1993.
1993, BAAS, 25, 1358.
9. Ghosh, T., Schilizzi, R. T., Miley, G. K., deBruyn, A. G., Kukula, M. J.,
Pedlar, A., Graham, D., Saikia, D. J.,
The milliarcsecond structure of four Seyfert galaxies at 18 cm., 1993, Proc. IAU
Symp. 159 on Active Galactic Nuclei across the electromagnetic spectrum, Ed:
Blecha, A., and Courvoisier, T. (Kluwer Academic Publishers, 1994), p426.
10. Ghosh, T., Gopal-Krishna, and Rao, A. P.,
Three year monitoring of a sample of at-spectrum radio sources at 327 MHz.
1994, A&A S, 106, 29
11. Iyengar D.R., Ghosh, T., Salter, C.J.,
Modeling the distribution of interstellar scattering at low latitudes,
1994, BAAS, 26, 1328.
12. Altschuler, D.A., Salgado, J.F., Dennison, B.K., Ghosh, T.,
Variability of extragalactic radio sources at low frequencies,
1994, BAAS, 26, 1503.
13. Jones, E.J., Ghosh, T.,
Radio-loud Seyfert Galaxies and their Environments,
1995, BAAS, 27, 1355.
14. Acevedo, F., Ghosh, T.,
Radio Frequency Interference: Radio Astronomy's Biggest Enemy
1997, BAAS, 191, 1101.
15. Salgado, J.F., Ghosh, T., Salter, C.J., Junor, W., Manoharan, P.K.,
Towards an understanding of the Galactic Distribution of Electron-Density Fluc-
tuations,
1997, I.A.U. Coll. No. 164
16. Eder, J., Ghosh, T., Kocevski, D.D.,
Dealing with the RFI Environment at Arecibo Observatory
1998, BAAS, 193, 1118.
17. Salter, C.J., Ghosh, T., et al.,
Single-Epoch Measurements of Broadband Radio Continuum Spectra, 1998,

BAAS, 193, 107225.
18. Kukula, M., Ghosh, T., Pedlar, A., Schilizzi, R.T.
Parsec-Scale Structures in the Nuclei of Four Seyfert Galxies
1999, ApJ, 518, 117.
19. Salgado, J.F., Ghosh, T., Altschuler, D.R., Dennison, B.K., Mitchell, K.J.,
Payne, H.E.,
14-year Program Monitoring the Flux Densities of 33 radio sources at low fre-
quencies.
1999, ApJ Suppl. 120, 77.
20. Ghosh T., Eder J.A., Salter C.J., Frierson, D.M., 2000, "Neutral Hydrogen
in Seyfert Galaxies - A Test for the Unication Scheme", ASP Conference Series;
"Gas and Galaxy Evolution", eds. J.E. Hibbard, M. Rupen, J.H. van Gorkom,
in press.
21. Hirabayashi et al.
The VSOP 5 GHz AGN Survey I. Compilation and Observations.
2000, PASJ, 52, 997.
22. Molotov, I.E., Chuprikov, A.A., Salter, C.J., Ghosh, T.,
The possibility for collaboration of Arecibo with international S2 ad-hoc array.
2001, AAS, 198.7501M.
23. Salter, C.J., Ghosh, T.,
Arecibo Spectral Baselines in the Presence of Continuum Emission.
2001, AAS, 198.75025
24. Kanekar, N., Ghosh, T., Chengalur, J.N.,
Detection of a multi-phase ISM at z= 0.2212.
2001, A &A, 373, 394.
25. Junor, W., Salter, C. J., Ghosh, T., and Saikia, D. J.
A radio source excess in the Zone of Avoidance { the 3C27 eld, cluster or
coincidence ?
2001, A &A, (in preparation).
26. Salter, C. J., Junor, W., Ghosh, T., and Saikia, D. J.
0042+6716 { An unusual radio source in the 3C27 region,
2001, A &A, (in preparation)
27. Ghosh, T., Eder, J., Salter, C.J., Frierson, D.
HI survey of a large unbiased sample of Seyfert Galaxies and testing the Unied
Scheme
2001, ApJ (in preparation)