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Empirical constraints of supergalactic winds at z ≳ 0.5

Gauthier, Jean-René and Chen, Hsiao-Wen (2012) Empirical constraints of supergalactic winds at z ≳ 0.5. Monthly Notices of the Royal Astronomical Society, 424 (3). pp. 1952-1962. ISSN 0035-8711. doi:10.1111/j.1365-2966.2012.21327.x.

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Under the hypothesis that Mg_(II) absorbers found near the minor axis of a disc galaxy originate in the cool phase of supergalactic winds, we carry out a study to constrain the properties of large-scale galactic outflows at redshift z_(gal) ≳ 0.5 based on the observed relative motions of individual absorbing clouds with respect to the positions and orientations of the absorbing galaxies. We identify in the literature four highly inclined disc galaxies located within 50 kpc and with the minor axis oriented within 45° of a background quasi-stellar object (QSO) sightline. Deep Hubble Space Telescope images of the galaxies are available for accurate characterizations of the optical morphologies of the galaxies. High-quality echelle spectra of the QSO members are also available in public archives for resolving the velocity field of individual absorption clumps. Three galaxies in our sample are located at ρ = 8–34 kpc and exhibit strong associated Mg_(II) absorption feature with W_r(2796) ≳ 0.8 Å. One galaxy, located at an impact parameters ρ = 48 kpc, dose not show an associated Mg_(II) absorber to a 3σ limit of W_r(2796) = 0.01Å. Combining known morphological parameters of the galaxies such as the inclination and orientation angles of the star-forming discs, and resolved absorption profiles of the associated absorbers at ρ < 35 kpc away, we explore the allowed parameter space for the opening angle θ_0 and the velocity field of large-scale galactic outflows as a function of z-height, v(z). We find that the observed absorption profiles of the Mg_(II) doublets and their associated Fe_(II) series are compatible with the absorbing gas being either accelerated or decelerated, depending on θ_0, though accelerated outflows are a valid characterization only for a narrow range of θ_0. Under an acceleration scenario, we compare the derived v(z) with predictions from Murray et al. and find that if the gas is being accelerated by the radiation and ram pressure forces from super star clusters, then the efficiency of thermal energy input from a supernova explosion is ∈ ≾ 0.01. In addition, we adopt a power-law function from Steidel et al. for characterizing the accelerated outflows as a function of z-height, a(z) ∝ z^(−α). We find a steep slope of α ≈ 3 for a launch radius of z_(min) = 1 kpc. A shallower slope of α ≈ 1.5 would increase z_(min) to beyond 4 kpc. We discuss the implications of these parameter constraints.

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Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 May 16. Received 2012 May 15; in original form 2012 April 11. Article first published online: 6 Jul. 2012. We thank C. Steidel, R. Trainor and Y. Matsuda for helpful discussions during the early stages of this project. We thank O. Agertz, N. Gnedin, A. Kravtsov, M. Rauch, G. Rudie, W. Sargent and A. Wolfe for helpful comments on an earlier version of the paper. We also thank C. Steidel for providing the optical spectrum of galaxy B in our study. J-RG gratefully acknowledges the financial support of a Millikan Fellowship provided by Caltech and of a Grant-In-Aid of Research from the National Academy of Sciences, administrated by Sigma Xi, The Scientific Research Society. This research has made use of the ESO Science Archive Facility and the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts.
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Caltech Millikan FellowshipUNSPECIFIED
National Academy of SciencesUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: general; galaxies: haloes; quasars: absorption lines; galaxies: star formation; galaxies: structure
Issue or Number:3
Record Number:CaltechAUTHORS:20121010-161911226
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Official Citation:Gauthier, J.-R. and Chen, H.-W. (2012), Empirical constraints of supergalactic winds at z≳ 0.5. Monthly Notices of the Royal Astronomical Society, 424: 1952–1962. doi: 10.1111/j.1365-2966.2012.21327.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34837
Deposited By: Aucoeur Ngo
Deposited On:11 Oct 2012 16:02
Last Modified:09 Nov 2021 23:10

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