Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/vscience/schedule/tpfiles/GuptatagA2488tp.pdf Дата изменения: Wed Apr 1 19:23:17 2009 Дата индексирования: Tue Aug 18 10:48:02 2009 Кодировка: Поисковые слова: ngc 6781

Proposal Identification No.:

A2488

Date Received:

2009-Mar-08 08:03:41

Technical Page
Proposal Type: General Category: Sub-Category: Observation Category: Total Time Requested: Minimum Useful Time: Prop osal Title: Regular Astronomy Spectroscopy Extragalactic 65 Hours 2hrs

Search for 21-cm absorption at 0.7 z 1.0 using optimally selected Mgii

absorbers.
ABSTRACT:
DLAs and strong metal absorption line systems seen in the spectra of high-z QSOs allow us to probe the physical conditions in protogalaxies. An important way of probing the thermal state of the ISM in these systems is by studying the 21-cm absorption in the spectra of background quasars. However, 21-cm absorption systems are very rare especially at high redshifts. From our just just completed systematic search of 21-cm absorption in an unbiased sample of 35 MgII systems at 1.10 z 1.45 (using 400hrs of GMRT time), we have found 9 new 21-cm absorbers. Further we find that 21-cm detection rate as high as 80% can be achieved by optimally selecting candidates on the basis of MgII, MgI and FeII absorption lines. Opening-up of 705-825MHz frequency-window at Arecibo provides the unique opportunity to uncover a good number of 21-cm absorbers for investigating the physical conditions in the ISM of the high-z galaxies. These observations can be used in combination with the various follow-up observations: (1) for investigating the physical conditions in the absorbing gas using spin temperature (TS ) measurements, (2) for investigating the effect of metallicity and dust content on the detectability of 21-cm absorption, (3) for studying the morphology of the absorbing gas and (4) for probing the time evolution of various fundamental constants. Here we request for 65hrs of time to search for 21-cm absorption in optimally selected MgII systems drawn from the entire SDSS database.

Name Neera j Gupta

Institution CSIRO Australia Telescope National Facility

E-mail Neera j.Gupta@atnf.csiro.au

Phone +61 93724295

2

Student no

Remote Observing Request

X

Observer will travel to AO Remote Observing In Absentia (instructions to operator)

Instrument Setup
1


705-825 Atmospheric Observation Instruments:

Sp ecial Equipment or setup:

none

RFI Considerations Frequency Ranges Planned
705-825

2