2009A&A...507..209L


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.23CET18:33:42

2009A&A...507..209L - Astronomy and Astrophysics, volume 507, 209-226 (2009/11-3)

Metal-rich absorbers at high redshifts: abundance patterns.

LEVSHAKOV S.A., AGAFONOVA I.I., MOLARO P., REIMERS D. and HOU J.L.

Abstract (from CDS):

To study chemical composition of metal-rich absorbers at high redshifts in order to understand their nature and to determine sources of their metal enrichment. From six spectra of high-z QSOs, we select eleven metal-rich, Z>Z, and optically-thin to the ionizing radiation, N(HI)<1017cm–2, absorption systems ranging between z=1.5 and z=2.9 and revealing lines of different ions in subsequent ionization stages. Computations are performed using the Monte Carlo inversion (MCI) procedure complemented with the adjustment of the spectral shape of the ionizing radiation. This procedure along with selection criteria for the absorption systems guarantee the accuracy of the ionization corrections and of the derived element abundances (C, N, O, Mg, Al, Si, Fe). The majority of the systems (10 from 11) show abundance patterns which relate them to outflows from low and intermediate mass stars. One absorber is enriched prevalently by SNe II, however, a low percentage of such systems in our sample is conditioned by the selection criteria. All systems have sub-kpc linear sizes along the line-of-sight with many less than ∼20pc. In several systems, silicon is deficient, presumably due to the depletion onto dust grains in the envelopes of dust-forming stars and the subsequent gas-dust separation. At any value of [C/H], nitrogen can be either deficient, [N/C]<0, or enhanced, [N/C]>0, which supposes that the nitrogen enrichment occurs irregularly. In some cases, the lines of MgII λλ2796, 2803 appear to be shifted, probably as a result of an enhanced content of heavy isotopes 25Mg and 26Mg in the absorbing gas relative to the solar isotopic composition. Seven absorbers are characterized by low mean ionization parameter U, logU←2.3, among them only one system has a redshift z>2 (zabs=2.5745) whereas all others are found at z∼1.8. This statistics is not affected by any selection criteria and reflects the real rise in number of such systems at z<2.0. Comparing the space number density of metal-rich absorbers with the comoving density of star-forming galaxies at z∼2, we estimate that the circumgalactic volume of each galaxy is populated by ∼107-108 such absorbers with total mass ≲1/100th of the stellar galactic mass. Possible effects of high metal content on the peak values of star-forming and AGN activities at z∼2 are discussed.

Abstract Copyright:

Journal keyword(s): line: formation - line: profiles - galaxies: abundances - intergalactic medium - quasars: absorption lines - cosmology: observations

Nomenclature: Table 1: [LAM2009] HEHHMM+DDMM abs N.NNNN N=10, [LAM2009] QHHMM+DDd abs N.NNNN N=1.

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 QSO J0003-2323 QSO 00 03 44.9144470879 -23 23 55.075352888     16.7     ~ 69 0
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9599 1
3 QSO J0143-3917 QSO 01 43 33.6332299840 -39 17 00.065618732     16.28     ~ 24 0
4 QSO J0153-4311 QSO 01 53 27.1919509912 -43 11 38.096734050     16.80     ~ 44 0
5 [CSP2004] QSO J0153-4311 abs 1.7319 ALS 01 53 27.2 -43 11 38           ~ 2 0
6 [BAP2002] QSO J0331-3824 abs 2.35214 ALS 03 31 06.34 -38 24 04.8           ~ 2 0
7 QSO B0329-385 QSO 03 31 06.3780192488 -38 24 04.653743031   17.63 16.92     ~ 75 0
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15049 1
9 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11817 0
10 [LCK2006] QSO J2350-4325 abs 1.79623 ALS 23 50 34.21 -43 25 59.6           ~ 3 0
11 QSO B2347-4342 QSO 23 50 34.2595236845 -43 25 59.680334378   16.3 16.3     ~ 160 0

    Equat.    Gal    SGal    Ecl

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