Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~tghosh/AN-rep2007.pdf Дата изменения: Thu Feb 11 01:48:01 2010 Дата индексирования: Sun Apr 10 00:29:46 2016 Кодировка: Поисковые слова: arp 220

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) в 10 -5 from the older WSRT data 1.85 and, [G/G] = (+1.94 ± 0.66) в 10-5 from the recent Arecib o data, where G g p 2 /µ , a combination of the fine structure constant , the electron-proton mass ratio µ m e /mp and the proton gyromagnetic ratio gp . Combining the two results weighted by their errors yields, [G/G] = (+9.5 ± 5.6) в 10-6 . Both results are consistent with no evolution in , µ 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.