期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 446, 期 1, 页码 18-37出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu2088
关键词
galaxies: haloes; quasars: absorption lines
资金
- European Southern Observatory (ESO) [166.A-0106, 185.A-0745, 091.A-0698]
- Paranal Observatory [091.A-0698]
- Australian Research Council [DP130100568]
- Science and Technology Facilities Council [ST/L00075X/1]
- STFC [ST/L00075X/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/L00075X/1] Funding Source: researchfish
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1109452] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1109115, 1109447] Funding Source: National Science Foundation
We report the serendipitous detection of a 0.2 L*, Ly alpha emitting galaxy at redshift 2.5 at an impact parameter of 50 kpc from a bright background QSO sightline. A high-resolution spectrum of the QSO reveals a partial Lyman-limit absorption system (N-HI = 10(16.94 +/- 0.10) cm(-2)) with many associated metal absorption lines at the same redshift as the foreground galaxy. Using photoionization models that carefully treat measurement errors and marginalize over uncertainties in the shape and normalization of the ionizing radiation spectrum, we derive the total hydrogen column density N-H = 10(19.4 +/- 0.3) cm(-2), and show that all the absorbing clouds are metal enriched, with Z = 0.1-0.6 Z(circle dot). These metallicities and the system's large velocity width (436 km s(-1)) suggest the gas is produced by an outflowing wind. Using an expanding shell model we estimate a mass outflow rate of similar to 5 M-circle dot yr(-1). Our photoionization model yields extremely small sizes (<100-500 pc) for the absorbing clouds, which we argue is typical of high column density absorbers in the circumgalactic medium (CGM). Given these small sizes and extreme kinematics, it is unclear how the clumps survive in the CGM without being destroyed by hydrodynamic instabilities. The small cloud sizes imply that even state-of-the-art cosmological simulations require more than a 1000-fold improvement in mass resolution to resolve the hydrodynamics relevant for cool gas in the CGM.
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