TY - JOUR
T1 - An aluminum-enhanced cloud in A C iv absorber at z = 1.94
AU - Ganguly, Rajib
AU - Churchill, Christopher W.
AU - Charlton, Jane C.
N1 - Funding Information:
This work was supported by NSF grants AST-9529242 and AST-9617185 and by NASA grant NAG 5-6399. Thanks to U. Hellsten for providing the Haardt and Madau input spectrum, and to J. Lauroesch, M. Rich, B. Savage, D. Schneider, S. Sigurdsson, R. Wade, and D. Welty for collectively contributing a breadth of knowledge. Special thanks to Steven S. Vogt for his years dedicated to building HIRES.
PY - 1998
Y1 - 1998
N2 - In the z = 1.94 C iv absorption-line system in the spectrum of quasar Q1222+228 (zem = 2.04), we find two clouds that have contrasting physical conditions, although they are only at a 17 km s-1 velocity separation. In the first cloud, Si II, Si IV, and C II are detected, and Al n and Al III column density limits in conjunction with photoionization models allow us to infer that this cloud has a large Si abundance and a small Al abundance relative to a solar abundance pattern. This pattern resembles that of Galactic metal-poor halo stars, which must have formed from such high-redshift gas. The second cloud, in contrast, has detected Al II and Al in (also Si IV and C II) but no detected Si n. We demonstrate, using photoionization models, that Al/Si must be greater than (Al/Si)odot; in this unusual cloud. Such a ratio is not found in absorption profiles looking through Milky Way gas. It cannot be explained by dust depletion since Al depletes more severely than Si. Comparing this cloud with other Al-rich environments, we speculate about the processes and conditions that could give rise to this abundance pattern.
AB - In the z = 1.94 C iv absorption-line system in the spectrum of quasar Q1222+228 (zem = 2.04), we find two clouds that have contrasting physical conditions, although they are only at a 17 km s-1 velocity separation. In the first cloud, Si II, Si IV, and C II are detected, and Al n and Al III column density limits in conjunction with photoionization models allow us to infer that this cloud has a large Si abundance and a small Al abundance relative to a solar abundance pattern. This pattern resembles that of Galactic metal-poor halo stars, which must have formed from such high-redshift gas. The second cloud, in contrast, has detected Al II and Al in (also Si IV and C II) but no detected Si n. We demonstrate, using photoionization models, that Al/Si must be greater than (Al/Si)odot; in this unusual cloud. Such a ratio is not found in absorption profiles looking through Milky Way gas. It cannot be explained by dust depletion since Al depletes more severely than Si. Comparing this cloud with other Al-rich environments, we speculate about the processes and conditions that could give rise to this abundance pattern.
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U2 - 10.1086/311323
DO - 10.1086/311323
M3 - Article
AN - SCOPUS:22044443343
SN - 0004-637X
VL - 498
SP - L103-L106
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART II
ER -