2018A&A...616A..29G


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST07:56:26

2018A&A...616A..29G - Astronomy and Astrophysics, volume 616A, 29-29 (2018/8-1)

Neutral gas properties of Lyman continuum emitting galaxies: Column densities and covering fractions from UV absorption lines.

GAZAGNES S., CHISHOLM J., SCHAERER D., VERHAMME A., RIGBY J.R. and BAYLISS M.

Abstract (from CDS):


Context. The processes allowing the escape of ionizing photons from galaxies into the intergalactic medium are poorly known.
Aims. To understand how Lyman continuum (LyC) photons escape galaxies, we constrain the HI covering fractions and column densities using ultraviolet (UV) HI and metal absorption lines of 18 star-forming galaxies that have Lyman series observations. Nine of these galaxies are confirmed LyC emitters.
Methods. We fit the stellar continuum, dust attenuation, metal, and HI properties to consistently determine the UV attenuation, as well as the column densities and covering factors of neutral hydrogen and metals. We used synthetic interstellar absorption lines to explore the systematics of our measurements. Then we applied our method to the observed UV spectra of low-redshift and z∼3 galaxies.
Results. The observed HI lines are found to be saturated in all galaxies. An indirect approach using OI column densities and the observed O/H abundances yields HI column densities of log(NHI)∼18.6-20cm–2. These columns are too high to allow the escape of ionizing photons. We find that the known LyC leakers have HI covering fractions less than unity.Ionizing photons escape through optically thin channels in a clumpy interstellar medium. Our simulations confirm that the HI covering fractions are accurately recovered. The SiII and HI covering fractions scale linearly, in agreement with observations from stacked Lyman break galaxy spectra at z∼3. Thus, with an empirical correction, the SiII absorption lines can also be used to determine the HI coverage. Finally, we show that a consistent fitting of dust attenuation, continuum, and absorption lines is required to properly infer the covering fraction of neutral gas and subsequently to infer the escape fraction of ionizing radiation.
Conclusions. These measurements can estimate the LyC escape fraction, as we demonstrate in a companion paper.

Abstract Copyright: © ESO 2018

Journal keyword(s): galaxies: ISM - ISM: abundances - ISM: lines and bands - ultraviolet: ISM - dust, extinction - dark ages, reionization, first stars

Simbad objects: 19

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Number of rows : 19

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9446 1
2 SHOC 148 Sy1 03 03 21.4140573561 -07 59 23.198200042     19.61     ~ 24 0
3 2MASX J04420810-3801108 H2G 04 42 08.110 -38 01 10.88 15.66 17.21 15.80 16.00   ~ 46 0
4 SDSS J091113.34+183108.1 Q? 09 11 13.3463735767 +18 31 08.195621007           ~ 16 0
5 2MASS J09215939+4509126 QSO 09 21 59.397 +45 09 12.38   18.57 18.31     ~ 48 0
6 SDSS J092532.36+140313.1 EmG 09 25 32.3641578796 +14 03 12.993552108           ~ 17 0
7 LARS 14 EmG 09 26 00.4041863336 +44 27 36.112149583           ~ 54 0
8 SDSS J105330.82+523752.8 Q? 10 53 30.8078248454 +52 37 52.791228755           ~ 17 0
9 SDSS J115204.88+340049.8 Q? 11 52 04.8912713190 +34 00 49.896063418           ~ 13 0
10 SGAS J122651.3+215220 LeG 12 26 51.3 +21 52 20           ~ 18 0
11 SDSS J124423.37+021540.4 EmG 12 44 23.376 +02 15 40.46           ~ 19 0
12 EC 12476-2317 AGN 12 50 18.90 -23 33 57.6   16.29 15.46     ~ 57 0
13 Mrk 54 GiC 12 56 55.638 +32 26 51.50   15.1       ~ 76 0
14 SDSS J133303.95+624603.8 H2G 13 33 03.96 +62 46 03.8           ~ 14 0
15 [ITS2007] 53531-1827-503 EmG 14 29 47.0055554613 +06 43 34.978722649           ~ 20 0
16 2QZ J144231.3-020952 Q? 14 42 31.3700739287 -02 09 51.961344010   20.28       ~ 16 0
17 SDSS J150342.82+364450.7 G 15 03 42.8276869198 +36 44 50.730581493           ~ 11 0
18 [BHG2011] SDSS J1527+0652 A1 LeG 15 27 48.950 +06 52 23.09           ~ 17 0
19 NAME Cosmic Eye G 21 35 12.730 -01 01 42.90           ~ 79 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-07:56:26

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