2001A&A...369...42K


Query : 2001A&A...369...42K

2001A&A...369...42K - Astronomy and Astrophysics, volume 369, 42-48 (2001/4-1)

HI 21 cm absorption in low (z) damped Lyman-α systems.

KANEKAR N. and CHENGALUR J.N.

Abstract (from CDS):

We report Giant Metrewave Radio Telescope (GMRT) 21 cm observations of two confirmed and one candidate low redshift damped Lyman-α systems (DLAS). HI absorption was detected in the two confirmed systems, at z=0.2378 and z=0.5247, with spin temperatures of 2050±200K and 330±70K respectively. The non-detection of absorption in the third (candidate) system places an upper limit on its optical depth, which in turn implies a 3σ lower limit of 850 K on its spin temperature. Ground based K-band imaging observations (Turnshek et al. 2000, in press) have identified the low Ts absorber with a spiral galaxy while the high Ts system appears to be an LSB galaxy. This continues the trend noted earlier by Chengalur & Kanekar (2000MNRAS.318..303C) of low spin temperatures for DLAS associated with spiral galaxies and high spin temperatures for those with no such association. Combining these new results with 21 cm observations from the published literature, we find that (1) The 21 cm equivalent width (EW21) of DLAS increases with increasing NHI. Further, absorbers associated with spiral galaxies have systematically higher EW21 at the same NHI than DLAS with no such association, (2) DLAS at high redshift (z>2) have small velocity spreads ΔV, while, at low redshift (z≲2), both large and small ΔV are observed. These trends are in qualitative agreement with hierarchical models of galaxy formation.

Abstract Copyright:

Journal keyword(s): galaxies: evolution - galaxies: formation - galaxies: ISM - cosmology: observations - radio lines: galaxies

Nomenclature: Table 1: [KC2001] QSO J0120-2701 abs N.NNNN N=1.

CDS comments: Table 1: The 2 other DLAs re already known: [RT2000] QSO J0954+1743 abs 0.2377, [RT2000] QSO J0830+2411 abs 0.5247.

Simbad objects: 13

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Number of rows : 13
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 QSO B0118-272 BLL 01 20 31.6628068344 -27 01 24.636341064   15.89 15.56 15.49   ~ 253 1
2 3C 48 QSO 01 37 41.2996631208 +33 09 35.080388820   16.62 16.20     ~ 2691 2
3 QSO J0441-4313 QSO 04 41 17.3385563928 -43 13 45.488722116   16.64 16.36 16.54 16.26 ~ 101 1
4 ICRF J054236.1+495107 Sy1 05 42 36.1380355416 +49 51 07.232213736   18.45 17.80 17.210   ~ 1393 1
5 ICRF J074110.7+311200 Sy1 07 41 10.7033429280 +31 12 00.230596416   17.02 16.89 16.322   ~ 428 1
6 3C 196 Sy1 08 13 36.0561170112 +48 13 02.644966020   18.36 17.79     ~ 515 2
7 7C 082754.29+242103.00 QSO 08 30 52.0861432224 +24 10 59.822369580   17.62 17.26 16.30   ~ 487 1
8 SDSS J083052.50+241101.9 G 08 30 52.44800 +24 11 01.1197   20.64       ~ 18 0
9 QSO J0854+2006 BLL 08 54 48.8749846272 +20 06 30.639583620   15.91 15.43 15.56   ~ 2182 1
10 QSO B0952+179 QSO 09 54 56.8238081784 +17 43 31.221444756   17.31 17.23     ~ 204 1
11 QSO J1130-1449 QSO 11 30 07.0523452128 -14 49 27.388021944   17.17 16.90 16 16.97 ~ 663 1
12 4C -02.55 QSO 12 32 00.0159535440 -02 24 04.793069304   17.41 17.06 16.4   ~ 401 1
13 3C 295 Sy2 14 11 20.467 +52 12 09.52   22.34 20.80 18.54   ~ 947 5

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2022.08.10-07:07:01

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