A survey of weak MgII absorbers at redshift <z>=1.78

Abstract

The exact nature of weak MgII absorbers (those with W_r(2796) < 0.3 A) is a matter of debate, but most are likely related to areas of local star formation or supernovae activity outside of giant galaxies. Using 18 QSO spectra obtained with the Ultra-Violet Echelle Spectrograph (UVES) on the Very Large Telescope (VLT), we have conducted a survey for weak MgII absorbers at 1.4 < z < 2.4. We searched a redshift path length of 8.51, eliminating regions badly contaminated by atmospheric absorption so that the survey is close to 100% complete to W_r(2796) = 0.02 A. We found a total of 9 weak absorbers, yielding a number density of absorbers of dN/dz = 1.06 +/- 0.12 for 0.02 <= W_r(2796) < 0.3 A. Narayanan et al. (2005) found dN/dz = 1.00 +/- 0.20 at 0 < z < 0.3 and Churchill et al. (1999) found dN/dz = 1.74 +/- 0.10 at 0.4 < z < 1.4. Therefore, the population of weak MgII absorbers appears to peak at z~1. We explore the expected evolution of the absorber population subject to a changing extragalactic background radiation (EBR) from z = 0.9 to z = 1.78 (the median redshift of our survey), and find that the result is higher than the observed value. We point out that the peak epoch for weak MgII absorption at z~1 may coincide with the peak epoch of global star formation in the dwarf galaxy environment.

arXiv comment25 pages, 14 figures, to be published in ApJ 01 March 2006, v639, 1

References in corpus (18)

• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• The Environmental Dependence of the Relations between Stellar Mass, Structure, Star Formation and Nuclear Activity in Galaxies
• Field Galaxy Evolution Since Z~1 from a Sample of QSO Absorption-Selected Galaxies
• Mg II Absorption Systems in SDSS QSO Spectra
• The Population of Weak Mg II Absorbers I. A Survey of 26 QSO HIRES/Keck Spectra
• Observations of Chemically Enriched QSO Absorbers near z ~ 2.3 Galaxies: Galaxy-Formation Feedback Signatures in the IGM
• The HST Quasar Absorption Line Key Project. XIV. The Evolution of Ly-alpha Absorption Lines in the Redshift Interval 0 to 1.5
• QSO Absorbing Galaxies at z<~1: Deep Imaging and Spectroscopy in the Field of 3C 336
• The physical properties of the Ly-Alpha forest at z > 1.5
• Specific Star Formation Rates to Redshift 1.5
• The power spectrum of the flux distribution in the Lyman-alpha forest of a Large sample of UVES QSO Absorption Spectra (LUQAS)
• The Population of Weak MgII Absorbers. II The Properties of Single-Cloud Systems
• Low and High Ionization Absorption Properties of Mg II Absorption-Selected Galaxies at Intermediate Redshifts. II. Taxonomy, Kinematics, and Galaxies
• The Kinematics of Intermediate Redshift Mg II Absorbers
• High Resolution STIS/HST and HIRES/Keck Spectra of Three Weak MgII Absorbers Toward PG 1634+706
• The star formation rate history in the FORS Deep and GOODS South Fields
• MgII Absorption through Intermediate Redshift Galaxies
• A Survey of Analogs to Weak MgII Absorbers in the Present

Cited by in corpus (16)

• The Physics of the Intergalactic Medium
• Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts
• A Survey of Weak MgII Absorbers at 0.4 < z < 2.4
• The Chemical and Ionization Conditions in Weak Mg II Absorbers
• A Bare Molecular Cloud at z~0.45
• The Physical Conditions of the Intrinsic N V Narrow Absorption Line Systems of Three Quasars
• The Kinematic Evolution of Strong MgII Absorbers
• MMT Survey for Intervening MgII Absorption
• Super-Solar Metallicity in Weak Mg II Absorption Systems at z ~ 1.7
• Physical Properties of Weak MgII Absorbers at z~2
• Galaxy Clusters in the Line of Sight to Background Quasars: II. Environmental effects on the sizes of baryonic halo sizes
• A cold metal-poor cloud traced by a weak MgII absorption at z~0.45. First detection of SiI, CaI and FeI in a QSO absorber
• Evolution of the Population of Very Strong MgII Absorbers
• Detection of Low Metallicity Warm Plasma in a Galaxy Overdensity Environment at z ~ 0.2
• Solar-Metallicity Gas in the Extended Halo of a Galaxy at $z\sim 0.12$
• The Advantage of Increased Resolution in the Study of Quasar Absorption Systems