. : http://www.naic.edu/~tghosh/AN-rep2007.pdf
: Thu Feb 11 01:48:01 2010
: Sun Apr 10 00:29:46 2016
:
Annual Rep ort of Academic Activity of Tapasi Ghosh (Mar07 - Feb08)

1. A brief Summary of Research and Scientific Activities : Variation of Fundamental Constants - current status of the pro ject: (Collab orators: N. Kanekar (NRAO), J. Chengalur (NCRA, India) Much of the interpretative work of the Arecib o data on this topic (pro ject, A2123: 40-hour integration on the OH satellite lines in the asso ciated absorb er of PKS 1413+135) happ ened this year. The result of the analysis so far imply, [G/G] = (-1.9 1.1) 10 -5 from the older WSRT data 1.85 and, [G/G] = (+1.94 0.66) 10-5 from the recent Arecib o data, where G g p 2 / , a combination of the fine structure constant , the electron-proton mass ratio m e /mp and the proton gyromagnetic ratio gp . Combining the two results weighted by their errors yields, [G/G] = (+9.5 5.6) 10-6 . Both results are consistent with no evolution in , or g p from the redshift of PKS 1413+135, i.e. over a lo okback time of 2.9 Gyrs. However, we note that the WSRT and the Arecib o results have similar magnitudes but opp osite signs (eventhough, they are consistent with each other within the resp ective 3-sigma values). Hence, we are now investigating if the "discrepancy" could b e due to an arithmatical error in one of the datasets. The WSRT observations were taken without any online Doppler shift, while Arecib o observations were taken with the Doppler shift applied as available at the observatory. The current effort is to use the same co de (develop ed by us) to re-calculate the helio centric velo city values from the observed (top o centric) frequencies for b oth data sets. Once this matter is settled, we would b e able to submit the pap er for publication. A cm-wavelength sp ectral line Census of ARP 220: (Collab orators: B. Catinella, M. Lebron, M. Lerner, R. Minchin, E. Momjian, C.J. Salter) Together with a ma jority of the (then) Arecib o radio astronomy group (Drs. Catinella, Lebron, Lerner, Minchin, Momjian and Salter ), I am participating in a pro ject to make a sp ectral scan of the prototyp e ULIRG, Arp 220. This pro ject uses the Arecib o receivers covering the 1.1 - 10 GHz band. The newly commissioned 800-MHz mo de of the WAPP sp ectrometer is b eing employed. The aim of the study is to investigate the various atomic/molecular line transitions detectable from this ULIRG. The large numb er of radio recombination lines present can b etter constrain RRL emission mo dels, while the molecular census will improve our understanding of how starbursts o ccur, and how the star formation rate is regulated. As well as "shaking down" the new WAPP mo de, the Double Position Switching (DPS) mo de of observing is a necessity for this pro ject, and an optimized mo dified DPS approach has b een develop ed. Ab out one half of the observations to ok place in the spring of 2007. These reveal a sp ectrum rich in molecular transitions, including the pre-biotic molecules, methanimine (C H2 N H ) in emission, three v2=1 direct l-typ e absorption lines of HCN, and an absorption feature from either 18OH or formic acid (HCOOH). Our results mark the first distant extragalactic detection of methanimine, a molecule with high relevance to the origins of life. In addition to detecting known absorptions lines of 6- and 5-cm excited OH, we have also revealed two, p ossibly three, absorption lines of 4-cm OH not previously seen in Arp 220, and a probable absorption feature from the 6.668-GHz line of methanol. Possible emission lines of CH and formamide (N H 2 C H O )


require confirmation. The first publication from this work has b een submitted to A.J. 2. Observing/Research-supp ort Prop osals: Jun 2007: Arecib o; Salter, C.J., Ghosh, T., Catinella, B., Lebron, M., Lerner, M., Minchin, R., Momjian, E., "A Cm-wavelength Search for Prebiotic (and Other) Molecules in Arp 220like Starburst Galaxies." Oct 2007: Arecib o; Kanekar, N., Ghosh, T., Salter, C.J., "A Blind Survey for redshifted H2CO 4.8 GHz Absorption towards a Radio-selected Sample." Oct 2007:Arecib o; Arce, H.C., Lebron, M., Ghosh, T., Gibson, S., Lerner, L., Minchin, R., Momjian, E., Salter, C.J., "A Cm-wave Molecular Line Census for Three Representative Interstellar Regions." Oct 2007:Arecib o; Zauderer, A., Momjian, E., Ghosh, T., Salter, C.J., "HI and Molecular Line Observations of the 2 Jy IRAS-NVSS Sample at L-Band." Oct 2007 (and re-submitted Feb 08):GBT; Ghosh, T., Salter, C.J., Catinella, B., Lebron, M., Lerner, M., Minchin, M., Momjian, E., O'Neil, K., "A GBT Cm-wave Search for Prebiotic & Other Molecules in Arp220-like Galaxies." Nov 2007:MERLIN; Ghosh, T., Salter, C.J., Momjian, E., Minchin, R., Lerner, M., Lebron, M., Catinella, B., "Mapping the Distribution of a Prebiotic Molecule, Methanimine, in Arp220." Nov 07:NSF Astronomy Grant Prop osal; Ghosh T., Lebron, M., Zauderer, L., "Cmwavelength Studies of Prebiotic and High-density Tracer Molecules in Starburst/Megamaser/Ultraluminous IR Galaxies." 3. List of Publications: Salter, C.J., Ghosh, T., Catinella, B., Lebron, M., Lerner, M.S., Minchin, R., Momjian, E., 2008, AJ, "The Arecib o Arp 220 Sp ectral Census I: Discovery of the Pre-Biotic Molecule Methanimine and New Cm-wavelength Transitions of Other Molecules", submitted. Kanekar, N., Chengalur, J. N., & Ghosh, T., "Probing Fundamental Constant Evolution with Redshifted OH Lines", 2008, Princeton Series in Astrophysics, 109 Ghosh, T., Catinella, B., Lebron, M., Lerner, M. S., Minchin, R., Momjian, E., & Salter, C. J., "The Detection of Prebiotic Molecules in the ULIRG Arp 220", 2007, American Astronomical So ciety Meeting Abstracts, 211, #141.07 Salter, C. J., Catinella, B., Ghosh, T., Lebron, M., Lerner, M. S., Minchin, R., & Momjian, E., "Excited-OH And Methanol Absorption In The ULIRG Arp220", 2007, American Astronomical So ciety Meeting Abstracts, 211, #141.06 Gupta, N., Salter, C. J., Saikia, D. J., Ghosh, T., & Jeyakumar, S., "Probing Radio Source Environments Using 21-cm Absorption", 2007, The Central Engine of Active Galactic Nuclei, 373, 203 Ghosh T. Salter, C.J., 2007, Galfacts Technical Memo No. 11, "The "Effects of Ionospheric Faraday Rotation on GALFACTS."


4. Other Academic Activities: In 2006, Chris Salter, Emmanuel Momjian and I jointly sup ervised REU Ximena Fernandez, in a pro ject entitled, "A Radio Sp ectral Line Study of NVSS Sample". Ximena continued with the pro ject for her final-year thesis at with "sup ervision from a distance", and an additional trip down to Arecib o Her thesis was successfully submitted in May 2007. student, Maria the 2-Jy IRASVassar College, in spring 2007.

In Jun 2007, at the Green Bank NAIC/NRAO Single Dish Summer Scho ol, I lectured on VLBI techniques, sup ervised students' hand-on pro ject of HI Galaxy search using the GBT in drift-scan mo de, and also ran a demonstration of Arecib o observation and data reduction using the offline CIMA and a set of pre-observed data (as this was during the telescop e down-time due to the ongoing platform painting). 5. VLBI related Technical Activities: Between April 2007 and Dec. 2008, all observations were susp ended due to painting of the platform. During that time, Chris Salter, Arun Venkataraman and I ran an eVLBI data transp ort exp eriment b etween Arecib o and JIVE using the UDP format over the existing OC3 connection. This was successful upto the data rate of ab out 105 Mbps. In Feb. 2008, we ran a realtime test, and was able to detect fringes for data rates of up to 128 Mbps. We have also run three HSA/Global VLBI observations in February 2008. All of these have b een successful. The observations represent; (1) a study of the Zeeman effects in compact comp onents of ULIRGs using circular p olarization observations of OH maser lines in these galaxies, (2) jet and counter-jet emissions in giant radio galaxy, NGC315, and (3) measuring the expansion velo city of SN 2008D asso ciated with the transient X-ray source in NGC 2770 (a target of opp ortunity). Post pro cessing of the SEFD monitoring data were also p erformed by myself for all these pro jects and provided to the users. During the year, I have also kept the FS software up-to-date by installing the package downloaded from the GSFC-VLBI Services group. 6. Meetings/Conferences/Official visitis June 07: Green Bank, NAIC/NRAO Single Dish Summer Scho ol. July 07: University of Calgary: To work with the GALFACTS team. Nov 07: The 3rd US-VLBI Technical meeting at Arecib oi. Jan 08: AAS meeting at Austin. Feb 08: HI conference at Arecib o (presented a p oster). 7. Academic Activities not covered Ab ove: I have presentated two talks to the 2007 AUSAC and NAIC-VC committees. I have (co)authored two white-pap ers for the Sep. 2007, DC meeting, "Frontiers of Astronomy with the World's Largest Radio Telescop e". These are: (1) Arecib o and High Resolution Astronomy, and (2) Probing Fundamental Constant Evolution with the Arecib o Telescop e. I have compiled a VLBI-equipment upgrade request for this year's Program plan.


I have organized the 3rd US-VLBI Technical workshop at Arecib o b etween 29th and 30th of Novemb er 2006. Jointly with Chris Salter, I have hosted a group of MIT-Alumni at Arecib o, arranging the logistics of the visit and the guided tour of the observatory. I have participated in the (remote, web-based) p oster sorting session for the Jan08 AAS meeting at Austin.