Open AccessThe connection between metallicity and metal‐line kinematics in (sub‐)damped Lyα systems
Author(s) -
Murphy M. T.,
Curran S. J.,
Webb J. K.,
Ménager H.,
Zych B. J.
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.11457.x
Subject(s) - physics , metallicity , astrophysics , redshift , rest frame , spectral line , line (geometry) , equivalent width , metal , absorption (acoustics) , quasar , kinematics , galaxy , emission spectrum , astronomy , optics , geometry , chemistry , mathematics , organic chemistry , classical mechanics
A correlation between the metallicity, [M/H], and rest‐frame Mg ii equivalent width, W λ2796 r , is found from 49 damped Lyα absorbers (DLAs) and strong sub‐DLAs drawn from the literature over the redshift range 0.2 < z abs < 2.6 . The correlation is significant at 4.2σ and improves to 4.7σ when the mild evolution of [M/H] with redshift is taken into account. Even when including only the 26 DLAs (i.e. excluding sub‐DLAs) which have Zn‐metallicities and W λ2796 r > 0.7 Å , the correlation remains at >3σ significance. Since the Mg ii λ2796 transition is predominantly saturated in DLAs (which always have W λ2796 r greater than 0.3 Å), W λ2796 r is far more sensitive to the kinematic spread of the metal velocity components across the absorption profile than it is to [M/H]. Thus, the observed [M/H]– W λ2796 r correlation points to a strong link between the absorber metallicity and the mechanism for producing and dispersing the velocity components. We also note that approximately half of the 13 known H 2 absorbers have very high W λ2796 r and very broad velocity structures which show characteristics usually associated with outflows. Follow‐up ultraviolet‐ and blue‐sensitive high‐resolution spectra of high‐ W λ2796 r systems, initially identified in low‐resolution spectra, may therefore yield a large number of new H 2 discoveries.