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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 an ten year old daughter. Fluency in Languages other than English: My mother tongue is Bengali (one of the 18 official languages in India), although I have been using English for more than 25 years and most of my formal education was in English. In addition, I have a limited command of Spanish, as well as a brief exposure to Dutch. EDUCATION: B.Sc. Physics (Hons) Lady Brabourne College, Calcutta, India. M.Sc. Physics Post M.Sc Associate (Bio-Physics) Ph.D (Astronomy) University College of Science, Calcutta, India. Saha Inst. of Nuclear Phys., Calcutta, India. 1979 1981 1982-83

Indian Inst. of Science, Bangalore, India. Thesis Topic: "Low-Frequency Variability of Compact Extragalactic Radio Sources"

1990

EMPLOYMENT: · Dec 1990 ­ Nov 1992: Post-doctoral Fellow, Netherlands Foundation for Research in Astronomy, Dwingeloo, The Netherlands. · Dec 1992 ­ Present: Research Associate with NAIC, at the Arecibo Observatory. Present responsibilities include coordinating all Very Long Baseline Interferometry (VLBI) related work and performing the absentee VLBI observations and the relevant system calibrations. I also provide general visiting observer support, and am responsible for calibration and documentation of the S-band receivers on the 305-m telescope. I annually supervise


"Research Experience for Undergraduate (REU)" summer students and carry on a personal astronomical research programme. CURRENT RESEARCH INTERESTS: I. Atomic and molecular gas in AGN host : The host galaxies of AGNs are difficult 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 difficulty, optical "fuzz" showing stellar spectra has been detected around nearby quasars using both ground-based telescopes and the HST. In addition, near-infrared imaging has been quite successful 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 ma jority 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 first 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 redshifts 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 ob ject, 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. In collaboration with various Radio Astronomers around the globe, I am carrying out the following pro jects in this area: 1. CSS/GPS Sources:

Collaborators: Drs C.J. Salter(NAIC/AO), D.J. Saikia (NCRA, India), Jeyakumar and Stutzki (U Cologne, Germany) Observations for an Arecibo and GMRT study/search HI absorption and OH emission/absorption in Compact Steep Spectrum (CSS) and GigaHertz Peaked Spectrum (GPS) radio sources was completed in March 2004. This has made use of the Double Position Switching technique developed by ourselves over recent years. The results include a first detection of deep HI absorption within the CSS galaxy, 3C258 (z = 0.165), and confirmation of a number of HI absorption detections by other telescopes, usually with better signal-to-noise. Upper limits are also placed on OH spectral lines for the sample. A global VLBI proposal to image the HI absorption in 3C258 is awaiting scheduling.


2. ARP 220: As a "Hands-On Experiment" for 4 students at the 2nd NAIC/NRAO School on "Single-Dish Radio Astronomy", held in Green Bank in Aug 2003, C. Salter and I supervised observations of HI and all 4 OH lines in the prototype starburst galaxy, Arp 220. The aim of the experiment was to illustrate the problems of baseline ripple due to standing waves when the source observed has significant continuum emission, and how this can be corrected by Double Position Switching. This end was well achieved by the students, but we had an added surprise in that the profiles measured for both satellite lines of OH were completely different to the previously published profiles of Baan and Haschick (1987). Our profiles contain velocity ranges where both emission and absorption are present. We believe that Baan & Haschick probably removed the absorption components in the spectra via their baseline fitting. The new profiles are now being written up for publication, including the four summer students among the authors. To interpret these complex OH satellite line profiles, we have recently acquired global VLBI data to image both of the satellite lines at milliarcsecond resolution. 3. PKS 1413+113: Collaborators: Nissim Kanekar (NRAO, USA), Jayaram Chengalur (GMRT, Inida) We have detected the two 18cm OH satellite lines from the z 0.247 source PKS1413+135; the 1720 MHz line in emission and the 1612 MHz line in absorption. The 1720 MHz luminosity is LOH 354L , more than an order of magnitude larger than that of any other known 1720 MHz maser. The profiles of the two satellite lines are conjugate, implying that they arise in the same gas. This allows us to test for any changes in the values of fundamental constants, without being affected by systematic uncertainties arising from relative motions between the gas clouds in which the different lines arise. Our data constrain changes in G gp [2 /y ]1.849 , where y me /mp , and are consistent with the different constants remaining unchanged from z 0.247 to today. If gp and me /mp are assumed to not vary, we obtain / = 0.6 ± 1.0 â 10-5 over the range 0 < z < 0.247. 4. Search for Water Vapour Masers in High-redshift AGNs: Collaborators: Smita Mathur (Ohio State Univ, USA), and C. J. Salter(NAIC/AO) Strong 22-GHz water-vapor masers have so far been detected in about 20 nearby AGNs. These "megamaser" sources are mostly associated with Seyfert 2 and LINER galaxies whose active nuclei are hidden by a large column density of optically obscuring, X-ray absorbing gas. Detailed studies of H2 O masers with VLBI imaging and spectral monitoring have become important tools for probing dense gas near the central engines of these sources, investigating the properties


of their accretion disks and measuring the masses of their (supermassive) black holes. Such studies have also been employed to estimate geometrical distances completely independent of the rungs of the extragalactic distance ladder. However, so far most of the detections of extragalactic H2 O masers have been in relatively nearby ob jects (with systemic velocities less than 7500 km/s), and (hence) in low-luminosity AGNs. To date, two searches of high-z water masers have been initiated using the 100-m Effelsberg telescope and the VLBA using the U, X, C and L-band receivers at those telescopes. Their observations are sensitive to flux densities of 20 and 40 ­ 50 mJy respectively. No detection has yet been reported. We notice that one of the selection criteria for these studies has been detectable X-ray flux in their targets. X-ray emission is an ubiquitous property of quasars, and indeed, according to models of X-rays are responsible for keeping the molecular gas "warm" enough for maser production. However, direct exposure to X-rays tend to make the gas too hot to form molecules, and the necessary condition for making the environment conducive for maser production appears to be substantial shielding from the X-ray source. Indeed al l the nearby maser sources, observed in X-rays, show large absorption in soft X-rays Thus, the appropriate selection criterion appears to be "soft X-ray absorption" instead of "detectable X-ray flux" which may, in fact, select against obscured sources. Hence, we have undertaken a and 2.70 ­ 4.55 using the X AGNs either with soft-X-ray torus such as compact steep H2 O-maser search in the redshift ranges 1.22 ­ 1.78 and C-band receivers of the 305-m telescope in 35 absorption or other indirect evidence of obscuring spectrum double radio structures.

Two sessions of observations have already been carried out in September and November 03 (A1785) covering about 25 % of our sample. During this time, the characteristics of the X-band receiver has improved by about 60 %. We are looking forward to completing this pro ject in the near future. I I. Damp ed Lyman- Absorb ers: 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 preferred in hierarchical structure formation theories, while a popular model in the observational literature assumes that DLAs are large, massive disks. Further, from local 21-cm emission line studies, it is expected that the absorption cross section is dominated by the disks of spiral galaxies. On the other hand, galaxies associated with DLAs appear to cover all morphological types, and are not confined to spirals alone. At present, I am involved in two pro jects in this area:


1. Unbiased search for Damped Lyman-alpha Absorbers at radio wavelengths: With Drs. C.J. Salter (NAIC/AO), and K. O'Neil (NRAO), I am searching for low-redshift Damped Lyman-alpha (DLA) systems via 21-cm absorption along the lines-of-sight to 200 compact distant radio sources. This will help improve both DLA statistics for 0 < z < 0.3, and knowledge of the HI mass fraction at z 0 . The detection level for these low redshift systems will enhance the studies of cosmological evolution of the nature and number density of DLAs, and their interstellar media. In addition, as the source sample is radio selected, dust obscuration will not bias the statistics. An initial epoch of this observation took place in Nov 03, and Feb 04. We have successfully used the Wideband Arecibo Pulsar Processor (WAPP) to acquire 400-MHz spectra, its first use in this mode and have developed an IDL-based analysis pathway. A regorous RFI-detection/flagging/excision method is also being developed to identify real signature of DLA systems in these spectra. The observations have already detected two DLA lines in a test run, both already known, but demonstrating the robustness of the approach. HI in High-z DLAs: Collaborators: Nissim Kanekar (NRAO, USA), Jayaram Chengalur (GMRT, Inida) Using the low-frequency capability of Arecibo 305-m telescope, we are searching for HI absorption in a high redshift (z 3.38) Damped Lyman- absorber (DLA) toward PKS 0201+113, and two other candidate DLAs at z 2.4 seen toward two radio loud quasars. Our observations are sensitive to 104 K gas in the z = 3.38 absorber providing the first possibility of detecting warm neutral medium at high redshifts. For the two z 2.4 DLAs, the observations, when completed will be sensitive to spin temperatures of 1000 K, a value typical of that in most damped systems. The observations will test an emerging trend that high-z DLAs predominantly contain the warm phase of HI, while both cold and warm HI are seen in low-z systems. The search also include OH absorption in two lower redshift absorbers at z 0.24 using the L-wide receiver to study chemical evolution of DLAs. I I I. VLBI survey of faint FIRST sources: With Drs. R. Porcas, W. Alef (MPIfR, Bonn) & C. Salter (NAIC), I am conducting a VLBI visibility survey of around 1000 faint (down to 1.4-GHz flux density of 1 mJy) sources selected from the VLA-FIRST survey. This will make use of the ultra-high sensitivity achievable with the Arecibo and Effelsberg telescopes at 21 cm using VLBA4/MK4 recording. The selected sources lie within the area of the Sloan Digital Sky Survey, and it is expected that 50be identified with SDSS ob jects down to m(V) 24 mag. Thus redshifts of many ob jects in


the sample should eventually become available. Amongst other uses, our survey will help identify the fraction of AGNs (as opposed to starburst galaxies) in the faint source population, and the number of faint targets existing for such future instruments as the high-resolution options for the SKA. IV. North Pp olar Spur: With Chris Salter (NAIC/AO), the first wide-area continuum imaging with the upgraded Arecibo telescope was made in 2000. This mapped an area of 6 deg x 6 deg at 430 MHz within the North Polar Spur (Loop I), where a semi-circular emission arc is superposed on the larger feature. This arc may represent the remnant of a second-generation supernova resulting from star formation within the compressed shell of Loop I, and is a promising candidate for the "reheating event" often invoked to explain the X-ray emission of Loop I. It is hoped that these highresolution total-power observations will aid understanding of the nature of the arc, and its relation to Loop I. Analysis of the data proved to be complicated due to the lack of many header parameters in the data format available at the epoch of observation. However, the reduction of the images was undertaken in the summer of 2003, in conjunction with REU student, Kit Reilly. Considerable progress had been made when Kit was killed in a tragic hiking accident. Dr Salter and I returned to the data later in the year, and produced a first map of the region which were presented at the Atlanta AAS meeting. It now remains to optimise these maps and to basket-weave the orthogonal coverages to produce a final image. V. Continuum Surveys with ALFA: With a number of members of the GALFA Continuum science subconsortium, Taylor (Calgary), Deshpande, Salter and Freire, a pilot survey towards a GALFA Continuum Survey is being made. This uses the L-wide receiver, and is exploring the effectiveness of the meridian NODding observing technique proposed for the full GALFA Continuum Transit Survey (GALFACTS). Two fields will eventually be mapped with Nyquist sampling. The data analysis pipeline is being developed for this study which will serve as the proptype for the full GALFACTS survey. SERVICE WORK AT ARECIBO OBSRVATORY: · VLBI related work: ­ I am a member of the Arecibo VLBI group, and have been actively involved in co-observing with the VSOP space antenna, HALCA, using a Canadian S2 recorder system. From the return to service of the upgraded telescope in mid 1997 until NASA tracking support for HALCA ceased recently, there have been 43 Arecibo VLBI observing runs. Jointly with Chris Salter, I have conducted all these observations including subsequent calibration, system checks and tape han-


dling. We had no 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 Major 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. Since then, I have been involved in testing/commissioning the recorder (along with three other members of the VLBI group). Since 2001 my main service role at Arecibo observatory has been to act as the "Friend of VLBI". With hardware and software support from Dr. John Hagen and Jeff Hagen at Arecibo, Chris Salter, Emmanuel Momjian and I have been carrying out VLBA-4 runs, co-observing with both the European VLBI Network and the VLBA of NRAO, USA. (see, http://www.naic.edu/astro/aovlbi) ­ In Apr 2004, the observatory acquired a disk-based Mark-5A recording system enhancing the corcording rate for VLBI observation from a maximum of 512 Mbits-per-sec to 1024 Mbits-per-sec. We integrated and tested the system and joined with the EVN in successful e-VLBI runs (http://www.naic.edu/astro/aovlbi/press release/eVLBI AR.htm). Regular use of the disk-recorder will begin soon. · Sp ectrum Management and RFI protection related work: Until April 2001, I was responsible for coordinating the local activities of the Spectrum Management and RFI-protection Group (SMARG) at Arecibo. This required working with a 10-member group consisting of engineers, software personnel, scientific staff and telescope operators to ensure that the radio-spectrum allocated to radio astronomy is maintained interference free and protected at Arecibo. This entailed minimising emissions from on-site equipment, monitoring the wider radio 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/rfiuser/main.html. · Visiting Observer Supp ort: As well as running VLBI observations, I have been the friend-of-the-telescope for a number of spectral line pro jects since the completion of the Arecibo upgrade seven years ago. · NAIC/AO Newsletter: Between Mar 1994 ­ Feb 2000, and Nov 2001 ­ Jul 2004 I have been the co-editor (along with Dr. Jonathan Friedman) of the AO/NAIC Newsletter. This is published approximately three times per year. This work has involved me in planning, editing and producing the Newsletter.


TEACHING-RELATED EXPERIENCE: Along with Chris Salter, I have supervised the doctoral thesis of Jos´ Francisco e Salgado from the University of Michigan (April 2000). I have supervised the following undergraduate summer students between 1993 and 2004 (in NSF's REU Program). The name, affiliation and pro ject title of each student is listed below: · 2003: Kit Reilly (deceased, New College, Fl.), "Continuum Mapping of NPS", Chris Salter is a co-invetigator in this pro ject. · 2002: Samantha Stevenson (Weslyan College), "Evolutionary Tracks of 12-micron sample Seyfert Galaxies", Leslie Hunt and JoAnn Eder are coinvestigators in this pro ject. · 2001: SunMi Chung (Weslyan College), " PKS1004+13: The Rosetta Stone for BAL Quasars ?", Chris Salter and Daniel Altschuler are co-investigators in this pro ject. · 1999: Dargan Frierson (North Carolina State University) "HI spectra of Seyfert Galaxies and testing the Unification Scheme". Jo Ann Eder and Chris Salter are co-investigators in this pro ject. · 1998: Monique Aller (Wellesley) "A Search for High Redshift Hydrogen Absorption in Radio-Loud Quasars". This used both the 430-MHz line and Gregorian feeds. The data analysis involved the development of various techniques for RFI excision. Mike Davis and Chris Salter are coinvestigators in this pro ject. · 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 then 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 offenders and their occupancy rates (the fraction of nights during which the RFI was present). This RFI information has helped many subsequent 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 Interference Monitoring Data collected round the Clock at Arecibo Observatory". The results provide valuable percentage occupancy plots for the various spectrum users as functions of both frequency and time of 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", "Engery Generation Mechanism in Astronomical sources", "AGNs", and "Radio Interferometry" to the AO summer students between 1993 and 2004. In addition, I have lectured at the First NAIC/NRAO Single-dish Summer School at Arecibo Observatory in 2001 and supervised 'hands-on' experiments in both the First and the Second NAIC/NRAO summer shcools in 2001, and 2003. 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, Linux 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 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 flux-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 identification of radio sources from Palomar Observatory Sky Survey (POSS) prints using fine-scale distance measuring machines at Ooty and Dwingeloo, and also from the digitised CDs of the POSS. · IDL : I have been using this rather extensively over the past two years.

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 different 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 flat-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., 1997, I.A.U. Coll. No. 164 Radio Emission from Galactic and Extragalactic Compact Sources, Astronomical Society of the Pacific Conference Series, Volume 144, eds. J.A. Zensus, G.B. Taylor, & J.M. Wrobel, P287. 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. Salgado, J.F., Salter, C.J., Ghosh, T., Manoharan, P.K., 1998, BAAS, 30, 1341. 19. Salter, C.J., Ghosh, T., Alejandro, A., Aller, M.C., Cordero, Y., Daubar, I., DeDeo, S., Kaplan, D.L., Kocevski, D.D., Mercado, F. A., Oppenheimer, B.D., Salmeron, C., 1998, BAAS, 30, 1414. 20. Salgado, J.F., Salter, C.J., Ghosh, T., Junor, W., Manoharan, P.K., 1999, BAAS, 31, 1373. 21. Frierson, D.M., Ghosh, T., Salter, C., Eder, J., 1999, BAAS, 195, No.115.14. 22. Kukula, M., Ghosh, T., Pedlar, A., Schilizzi, R.T. Parsec-Scale Structures in the Nuclei of Four Seyfert Galxies 1999, ApJ, 518, 117. 23. 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 frequencies. 1999, ApJ Suppl. 120, 77. 24. Ghosh T., Eder J.A., Salter C.J., Frierson, D.M., 2000, "Neutral Hydrogen in Seyfert Galaxies - A Test for the Unification Scheme", ASP Conference Series; "Gas and Galaxy Evolution", eds. J.E. Hibbard, M. Rupen, J.H. van Gorkom. 25. Hirabayashi et al. The VSOP 5 GHz AGN Survey I. Compilation and Observations. 2000, PASJ, 52, 997. 26. Molotov, I.E., Chuprikov, A.A., Salter, C.J., Ghosh, T., The possibility for collaboration of Arecibo with international S2 ad-hoc array. 2001, BAAS, 33,899. 27. Salter, C.J., Ghosh, T., Arecibo Spectral Baselines in the Presence of Continuum Emission. 2001, BAAS, 33, 900. 28. Kanekar, N., Ghosh, T., Chengalur, J.N., Detection of a multi-phase ISM at z= 0.2212. 2001, A &A, 373, 394. 29. Heiles, C., Perillat, P., Nolan, M., Lorimer, D., Bhat, N.D.R., Howell, E., Ghosh, T., Lewis, M., O'Neil, K., Salter, C., and Stanimirovic, S., All Stokes Parameterization of the Main Beam and First Sidelobe for the Arecibo Radio Telescope. 2001, PASP, 113, 1247.


30. Heiles, C., Perillat, P., Nolan, M., Lorimer, D., Bhat, N.D.R., Howell, E., Ghosh, T., Lewis, M., O'Neil, K., Salter, C., and Stanimirovic, S., Mueller Matrix Parameters for Radio Telescopes and Their Observational Determination, 2001, PASP, 113, 1274. 31. Ghosh, T., Aller, M., Salter, C.J., and Davis, M.M., A Neutral Hydrogen Search for the Host Galaxies of 18 RadioLoud Quasars, 2001, I.A.U. Symp. No. 199, 127. 32. Ghosh, T., "Spectrum Management", ASP Conference Series; "NAIC/NRAO School on Single-Dish Radio Astronomy: Techniques and Applications", eds. S. Stanimirovic, D.A. Altschuler, P.F. Goldsmith, C.J. Salter, 2002, 447. 33. Ghosh, T., Salter, C.J., 2002, "Arecibo Spectral Baselines in the Presence of Continuum Emission", ASP Conference Series; "NAIC/NRAO School on Single-Dish Radio Astronomy: Techniques and Applications", eds. S. Stanimirovic, D.A. Altschuler, P.F. Goldsmith, C.J. Salter, 2002, 52 34. Molotov, I., Chuprikov, A., Likhachev, S., Salter, C.J., Ghosh, T., Ghigo, F., Dougherty, S., 2002, "First VLBI Observations with Arecibo in an International S2 Ad-hoc Array", ASP Conference Series; "NAIC/NRAO School on Single-Dish Radio Astronomy: Techniques and Applications", eds. S. Stanimirovic, D.A. Altschuler, P.F. Goldsmith, C.J. Salter, 2002, 507. 35. Stevenson, S.L., Hunt, L.K., Ghosh, T., Eder, J. "HI Evolutionary Studies of IR-Selected AGNs", 2002, BAAS, 201.5205 36. Salter, C.J., Jeyakumar, S., Saikia, D.J., Ghosh, T., Stutzki, J., HI Absorption towards Compact Steep Spectrum Radio Sources, 2003, BAAS, 202.4210 37. Reilly (deceased), K., Salter, C.J., Ghosh, T., Continuum mapping of an interaction Region within Loop-I (the North Polar Spur) in the ISM, 2003, BAAS, 20311015 38. Ghosh, T., Kavars, D.W., Robinson, R.E., Saintonge, A., Strasser, S.T., Salter, C.J., High Sensitive Observatations of the Satellite OH Lines of Arp 220, 2003, BAAS, 20311508 39. Kanekar, Nissim, Chengalur, Jayaram N., Ghosh Tapasi, Conjugate 18-cm OH satellite Lines at a Cosmological Distance, 2004, PhRvL, 93, 1302


40. Zahid, J., DeCesar, M., Kinnaman, L., Rice, M., Saucedo-McQuade, K., Ghosh, T., Momjian, E., Salter, C.J., 2004, BAAS, "Neutral Hydrogen in the Galaxy Cluster, Abell 2390", In Press. 41. Momjian, E.,Ghosh, T., Salter, C.J., Venkataraman, A., 2004, BAAS, "eVLBI observations with the 305m Arecibo Radio Telescope", In Press. 42. Taylor, G.B., Momjian, E., Pihlstroem, Y., Ghosh, T., Salter, C.J., 2004, ApJ, "Late Time Observations of the Afterglow and Environment of GRB 030329", Submitted.