Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~tghosh/AN-rep2008.pdf Дата изменения: Thu Feb 11 01:48:01 2010 Дата индексирования: Sun Apr 10 00:29:55 2016 Кодировка: Поисковые слова: arp 220

Annual Report of Academic Activity of Tapasi Ghosh (April 08 - March 09)

1. A Summary of On-going Research and Scientific Activities: Variation of Fundamental Constants - current status of the pro ject: (Collab orators: N. Kanekar (NRAO), J. Chengalur (NCRA, India) [This pro ject has a longer history than just the past year, and involves two different pro ject IDs, A2123 and A2386 for the Arecib o part of it. The description b elow also has to span at least the last two years so that some asp ects of this pro ject can b e put into context] (a) The first 40 hours of observation (A2123) of the OH-conjugate satellite lines of PKS1413+135 in late 2006 provided us with a puzzle. By early 2008, the result of our analysis implied, [G/G] = (-1.9 ± 1.1) в 10-5 from the older WSRT data and, [G/G] = (+1.94 ± 0.66) в 10-5 from the 1.85 Arecib o data, where G gp 2 /µ , a combination of the fine structure constant , the electronproton mass ratio µ me /mp and the proton gyromagnetic ratio gp . Combining the two results weighted by their errors yielded, [G/G] = (+9.5 ± 5.6) в 10-6 . Both results were found to b e consistent with no evolution in , µ or gp from the redshift of PKS 1413+135, i.e. over a look-back time of 2.9 Gyr. However, we noted that the WSRT and the Arecib o results signs (even though, they are consistent with each other to The WSRT observations were made without any online Dop taken with the Doppler correction applied as is available at have similar magnitudes but opp osite within the resp ective 3-sigma values). pler shift, while the Arecib o data were the Observatory.

This led us to use the same off-line code (develop ed by us) to re-calculate the heliocentric velocity values from the observed (top ocentric) frequencies for b oth data sets. It was found that there was ab out a 3 km/s offset b etween the absolute (heliocentric) velocity values of the OH lines derieved from the Arecib o and the WSRT sp ectra. (b) In order to resolve this discrepancy, and also to improve the signal-to-noise ratio of our detection by a factor of 2, we requested a further 40 hours observing time (and the use of a stronger bandpass calibrator to reduce the noise) in February 2008. This was granted and the observations were taken in the summer of 2008, this time without using online Doppler tracking. The resulting sp ectra then agreed completely with the WSRT sp ectrum in their absolute velocity values. We have also conducted further tests of Arecib o's current doppler tracking routines. Results so far indicate that in 2006, (at the time of observing of A2123), the online doppler tracking in CIMA and WAPP data-taking software may have b een erroneous. As yet, we do not know what corrections can b e applied to the 2006 data in order to combine with the 2008 data. However, we hop e to bring this pro ject to a conclusion within the next few months. A Blind Survey for Redshifted H2 C O 4.8-GHz Absorption Towards a Radio-Selected Sample. (Collab orators: N. Kanekar (NRAO), C.J. Salter (AO/NAIC) Using Arecib o's S-low, S-high and C-band receivers we are carrying out a blind survey for redshifted H2 C O 4.83-GHz absorption towards a complete radio-selected sample of 155 sources. The survey is sensitive to molecular absorb ers in the redshift range 0.03 < z < 0.85 and 1.01 < z < 1.3 and allows an estimate of the probability of finding a molecular absorb er p er unit redshift interval, as well as the cosmological mass density of molecular gas in the ab ove z-range. Observations are progressing 1


and data analysis and interpretation will b e carried out over the coming months. 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) The observations for this pro ject are now essentially complete. The new 800-MHz mode of the WAPP sp ectrometer was commissioned through the observations for this pro ject. The sp ectral scan has b een used to search for new detections of molecular lines from Arp 220, and will measure recombination lines (RRLs) across the full 1-10 GHz band, constraining the prop erties of its ISM. Previously undetected molecular sp ecies (e.g. C H2 N H , HCN v2 =1, excited OH, CH, C H3 OH and 18 OH/H C OOH ) have b een found in emission and absorption, with RRLs detected down to 3 GHz; the data b elow 3 GHz has not yet b een co-added to extend this search to 1.1 - 3 GHz. RRLs were not previously detected b elow 8 GHz. MERLIN observations of the distribution of C H2 N H in Arp220 are complete, and await imaging by an REU student in the summer of 2009. An Arecib o/GBT Cm-wavelength Search for Prebiotic (and Other) Molecules in Arp 220-like Starburst Galaxies. : (Collab orators: B. Catinella, M. Lebron, M. Lerner, R. Minchin, E. Momjian, C.J. Salter, K. O'Neil) The aim of this pro ject is to conduct a complimentary Arecib o/GBT molecular line search in the (rest-frame) frequency range of 4200 ­ 5400 MHz, covering transitions of HCO+ , HCN, NH2 CHO, excited-OH, H2 CHO, CH, and CH2 NH which lie at rest frequencies of 4234, 4489, 4619, 4660­4765, 4829, 4848, and 5289 MHz resp ectively in forty, Arp220-like galaxies. The sample was selected on the basis of existing data on OH megamasers, formaldehyde emission, optical emission lines in FIR luminous galaxies, and compact ULIRG starbursts. Almost 50 % of the Arecib o data (those for 9 galaxies) are fully analysed, and molecular lines/RRLs detected in 4, p ossibly 5. The galaxies IC860 and Zw049.057 seem to b e quasi-exact molecular analogs of Arp 220, with C H2 N H , HCN (v2 = 1), OH, H2 C O (b oth 4829, and 4954 MHz) b eing detected. In addition, in a short opp ortunistic observation with the CBH receiver, b oth galaxies showed the 6.03-GHz OH main lines in absorption, the J=5 absorption line of HCN (v2 = 1), and a numb er of other candidate molecular lines that we intend to follow up. The GBT observations are partly complete. Data analysis will continue through the summer of 2009. A Cm-wave Molecular Line Census for Two Representative Interstellar Regions: (Collab orators: H. Arce (Yale), M. Lebron(UPR), T. Ghosh, .... et al.) As a precursor for a full consortium pro ject to obtain sp ectral scans of star-forming (and other) regions in our Galaxy, the full frequency ranges of the LBW, CB, CBH and XB were searched against the high-mass star-forming region, NGC2264, and the proto-planetary nebula, CRL618. We originally prop osed to use the Mock sp ectrometers in single-pixel mode to examine the full 1 GHz wide bands available from the receivers at a "single shot". Sadly, this mode was not ready in time, and we were forced to fall back on the 8-b oard WAPP mode, with a maximum instantaneous bandwidth of 340 MHz. However, while the desired sensitivity and frequency coverage was not achieved, highly interesting results were still obtained. For NGC 2264, lines of C H3 OH, H2 C O and 1 H2 3 C O were seen in absorption, with the X-band H C3 N lines b eing detected in emission. The main lines of 18-cm OH are found to b e maser emitting, while the corresp onding satellite OH lines are conjugate (1612 MHz in emission, 1720 MHz in absorption.) Although the sp ectrum of CRL618 is less rich, exceedingly interesting, strong (150 mJy/b eam), maser emission was discovered in the 2


4765-MHz satellite line of excited-OH. GALFA Continuum Transit Survey (GALFACTS): (Collab orators: The GALFACTS consortium; PIs. A.R. Taylor, & C. J. Salter) I have participated in the data acquisition and Stage-I data reduction of the commensal IGALFA/GALFACTS/ZOA survey pro ject, A2186. The first section of these observations were completed in the summer of 2008. The main GALFACTS survey commenced in Novemb er 2008, with a 90 x18 field, including the Galactic anticenter region north of the Arecib o zenith, b eing mapp ed. The data has now b een transferred to Calgary, and will soon b e passed through the reduction pip eline. Scientifically, my focus area within GALFACTS is the study of time-varying sources. I exp ect to devote considerable time to developing software for this purp ose, in collab oration with other team memb ers in this sub-consortium. 2. Observing/Research-supp ort Prop osals: · Feb 2008: Arecib o; Taylor, A.R., Salter, C.J.,..., & Ghosh, T., and the GALFACTS subconsortium, "GALFACTS Commensal Observing with I-GALFA" (A2390). · Feb 2008: 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." · Feb 2009: Arecib o; Arce, H.G., Lebron, M.E., ....., Ghosh, T., et al., "The Arecib o Galactic Chemistry Survey" (A2463). · Mar 2009: Arecib o; Arce, H.G., Lebron, M.E., ...., Ghosh, T., et al., "Extending the Arecib o Galactic Chemistry Survey to 770 MHz" (A2489). · Mar 2009: Arecib o; Chandola Y., Saikia, D.J., ...., Ghosh, T., et al., "Probing Radio Source Environments via HI and OH Absorption" (A2495). · Mar 2009: Arecib o; Salter, C.J., Minchin, R., Ghosh, T., et al., "A 720-820 MHz Line Search in Arp220 and Arp 220-look-alike Galaxies" (A2496). · August 08:NSF PAARE Program : I have taken an active part in developing a collab orative program under the auspices of NSF PAARE program for fostering collab orative research and training work in radio astronomy using a prop osed 12-m class dish at the Observatory with the University of Puerto Rico, Humacao. · Nov 08: NASA Astrobiology Program : I have contributed in this observatory-wide effort (as yet unsuccessful) to establish a NASA astrobiology center. · NSF CREST Center Prop osal : I have contributed in this prop osal writing effort of the observatory colleagues in collab oration with the Universidad Metrop olitana. 3. List of Publications: · Salter, C.J., Ghosh, T., Catinella, B., Lebron, M., Lerner, M.S., Minchin, R., Momjian, E., 2008, "The Arecib o Arp 220 Sp ectral Census I: Discovery of the Pre-Biotic Molecule Methanimine and New Cm-wavelength Transitions of Other Molecules", AJ, 138, 389. 3


· Kanekar, N., Chengalur, J. N., & Ghosh, T., "Probing Fundamental Constant Evolution with Redshifted OH Lines", 2008, Princeton Series in Astrophysics, 109 · Salter, C.J., Catinella B., Ghosh, T., Lebron M., Lerner M.S., Minchin R., Momjian E., & Salter C.J., 2008, "Excited-OH And Methanol Absorption in the ULIRG Arp220", BAAS, 211, 39, 992 · Ghosh, T., Catinella B., Lebron M., Lerner M.S., Minchin R., Momjian E., & Salter C.J., 2008, "The Detection of Prebiotic Molecules in the ULIRG Arp 220", BAAS, 39, 992 · Hernandez, H., Ghosh, T., Salter, C. J., & Momjian, E., 2008, "The Evolution of Galaxies Through the Neutral Hydrogen Window", Eds. Minchin, R., Momjian, E., AIP Conference Proceedings, 1035, 214 · Minchin, R.F., Catinella, B., Ghosh, T., Lebron, M., Lerner, M., Momjian, E., O'Neil, K., Salter, C., 2009, "A Cm-Wavelength Search for Pre-Biotic Molecules in Starburst Galaxies", BAAS, 41, 328 4. Other Academic Activities: · Since January 2009, I have b een co-sup ervising Ashley Zauderer of University of Maryland on her PhD thesis pro ject. She is financially supp orted from a NSF grant for which I am the P.I. · During the last year, I have worked with a group at the Observatory to refine the need for, and sp ecify the parameters of a small telescop e that will b e used for, (i) phase-referenced VLBI observations with the 305-m dish, (ii) used as a teaching tool by the UPR students (via the PARRE prop osal, and (iii) also used for geodetic VLBI (via the VLBI2010 program). 5a. User Supp ort : A2383 I have b een the "Friend of the Telescop e" for the pro ject, "Monitoring a water megamaser in the early universe" (P.I. Paola Castangia). Dr. Castangia and her collab orators were new observers for Arecib o, and required a sp ecial calibration path way. I introduced their group to the telescop e, worked out a calibration scheme (in consultation with Chris Salter), and wrote several IDL codes to facilitate this. 5c. User Supp ort : Single-Dish Pulsar data on VLBI recorder The Usage of the Mark5A recorder for baseband-sampled pulsar data has b ecome quite p opular at the observatory for studies of Interstellar scintillations. Often multiple backends are also used for such pro jects. For all such observations, I have help ed the users with their setup-file preparations, data-taking, p ost-observation file transfers and calibrations. The pro jects in this category are P2395, P2445, P2362, and P2419 (PIs. Ryan Shannon, Paul Demorest, & Dan Stinebring) 5c. User Supp ort : VLBI In 2008, Arecib o participated in all three EVN sessions, many HSA, eVLBI, and Ultra-wide band VLBI runs. Details of some of these observations follow: (a) On May 5th 2008, e-VLBI was p erformed with an array including Harteb eesthoek Radio Astronomy Observatory in S. Africa. Fringes were obtained at 32 Mbps, limited by HRAO's available data rate. This run used the old ATM fib ers in Puerto Rico and was the first US-Africa e-VLBI. (b) On May 9th, e-VLBI was successfully p erformed with the 6-m TIGO dish at Concep cion, Chile. This also used the old ATM fib ers and was the first North-South American e-VLBI fringes. 4


(c) An Ultra Wideband VLBI (UW-VLBI) test run was conducted on May 15th, b etween the GBT and AO, at 4 Gbps. Disc recording using a DBE (Digital Backend) and 2 x Mk5B+ recorders on loan from Haystack was made. Ten seconds of data were then transferred via ftp to Haystack, and correlated there. In 10 sec, 1700:1 SNR fringe was obtained on a 122 mJy source, the most sensitive interferometric baseline yet obtained anywhere! (d) Between 17-18th May, "production" disc-recording of UW-VLBI at 4 Gbps was made. Data were recorded for complete transits at AO of a numb er of gravitationally-lensed radio sources to search for the presence of weak central images to the total lensed images. Data recorded at Ar and GBT were then successfully correlated at Haystack. Further results are awaiting the imaging and analysis. The DBE and Mk5B+ systems were subsequently returned to Haystack. (e) On 20th May, an e-VLBI test session was carried out with Westerb ork, Onsala, Medicina, Cambridge, Torun, and Jodrell Bank, with the data correlated in real time at JIVE in the Netherlands. Successful sustained fringes at 128 and 256 Mbps were obtained with data from Arecib o. (The previous b est was 105 Mbps.) Fringes were briefly obtained at 512 Mbps, but technical development was deemed necessary to sustain this data rate. This was the first usage of the new Centennial de PR fib ers. (f ) On May 22nd, the Arecib o telescop e joined with other memb ers of the EXPReS pro ject in a live demonstration of the first ever real-time e-VLBI observations that simultaneously used telescop es in North America, South America, Europ e and Africa. This simulated a telescop e almost 11,000 kilometers in diameter. The results were immediately transmitted to Bruges, Belgium, as part of a live demonstration at the TERENA (Trans-Europ ean Research and Education Networking Association) Networking Conference 2008. (g) On 9th Septemb er, we were able to Europ ean EVN telescop es at a rate of the network connectivity from Puerto infrastructure jointly develop ed by the and a dedicated network path (VLAN) demonstrate real-time fringes b etween Arecib o and several 512 Mbps. This was made p ossible by improvements in Rico to the mainland USA via the PRISANET gigabit University of Puerto Rico, Centennial of PR, and the AO, all the way from Arecib o to JIVE in The Netherlands.

(h) The IYA-2009 Op ening Ceremony in Paris on 15th January had a 24-hour eVLBI demonstration session, in which Arecib o participated for ab out 6 hours. During that time, we hosted visitors in the control room, and explained VLBI/astronomy to them. Many of these were our colleagues, and the event was well accepted. All these observations were carried out by Chris Salter and myself with hardware and software supp ort from the Electronics and Computing Departments. Post processing 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 visits · May/June 08: AAS meeting at St. Louis, MO. 7. Academic Activities not covered Ab ove: · I have presented two talks to the 2008 AUSAC and NAIC-VC committees. · Along with Chris Salter, I have organized the EVN Consortium Board of Directors meeting at the Observatory b etween 3rd and 4th Novemb er 2008.

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