J/A+A/663/A59 Low-Redshift Lyman Continuum Survey (Saldana-Lopez+, 2022)
The Low-Redshift Lyman Continuum Survey. Unveiling the ISM properties of
low-z Lyman-continuum emitters.
Saldana-Lopez A., Schaerer D., Chisholm J., Flury S.R., Jaskot A.E.,
Worseck G., Makan K., Gazagnes S., Mauerhofer V., Verhamme A., Amorin R.O.,
Ferguson H.C., Giavalisco M., Grazian A., Hayes M.J., Heckman T.M.,
Henry A., Ji Z., Marques-Chaves R., McCandliss S.R., Oey M.S., Ostlin G.,
Pentericci L., Thuan T.X., Trebitsch M., Vanzella E., Xu X.
<Astron. Astrophys., 663, A59 (2022)>
=2022A&A...663A..59S 2022A&A...663A..59S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Ultraviolet ; H I data ; Equivalent widths
Keywords: ISM: structure - dust, extinction - galaxies: ISM -
galaxies: starburst - galaxies: stellar content -
ultraviolet: galaxies
Abstract:
Combining 66 ultraviolet (UV) spectra and ancillary data from the
recent Low-Redshift Lyman Continuum Survey (LzLCS) and 23 LyC
observations by earlier studies, we form a statistical sample of
star-forming galaxies at z∼0.2-0.4 with which we study the role of
cold interstellar medium (ISM) gas in the leakage of ionizing
radiation. We also aim to establish empirical relations between the HI
neutral and low-ionization state (LIS) absorption lines with different
galaxy properties.
We first constrain the massive star content (stellar ages and
metallicities) and UV attenuation by fitting the stellar continuum
with a combination of simple stellar population models. The models,
together with accurate LyC flux measurements, allow us to determine
the absolute LyC photon escape fraction for each galaxy
(fescabsfescabs). We then measure the equivalent widths and
residual fluxes of multiple HI and LIS lines, and the geometrical
covering fraction of the UV emission, adopting the picket-fence model.
The LyC escape fraction spans a wide range, with a median
fescabsfescabs (0.16, 0.84 quantiles) of 0.04 (0.02, 0.20),
and 50 out of the 89 galaxies detected in the LyC (1σ upper
limits of fescabs≤0.01 for non-detections, typically). The HI and
LIS line equivalent widths scale with the UV luminosity and
attenuation, and inversely with the residual flux of these lines.
Additionally, Lyα equivalent widths scale with both the HI and
LIS residual fluxes, but anti-correlate with the corresponding HI or
LIS equivalent widths. The HI and LIS residual fluxes are correlated,
indicating that the neutral gas is spatially traced by the
low-ionization transitions. We find that the observed trends of the
absorption lines and the UV attenuation are primarily driven by the
geometric covering fraction of the gas. The observed nonuniform gas
coverage also demonstrates that LyC photons escape through
low-column-density channels in theISM. The equivalent widths and
residual fluxes of both the HI and LIS lines strongly correlate with
fescabs : strong LyC leakers (highest fescabs) show weak
absorption lines, low UV attenuation, and large Lyα equivalent
widths. We provide several empirical calibrations to estimate
fescabs from UV absorption lines. Finally, we show that
simultaneous UV absorption line and dust attenuation measurements can,
in general, predict the escape fraction of galaxies. We apply our
method to available measurements of UV LIS lines of 15 star-forming
galaxies at z∼4-6 (plus 3 high-z galaxy composites), finding that
these high-redshift, UV-bright galaxies (MUV≤-21) may have low
escape fractions, fescabs≤0.1.
UV absorption lines trace the coldISM gas of galaxies, which governs
the physics of the LyC escape. We show that, with some assumptions,
the absolute LyC escape can be statistically predicted using UV
absorption lines, and the method can be applied to study galaxies
across a wide redshift range, including in the epoch of cosmic
reionization.
Description:
We use UV spectra in the observed frame wavelength range 800-1950Å
from the Low-Redshift Lyman Continuum Survey (LzLCS, Flury et al.,
2022ApJS..260....1F 2022ApJS..260....1F, Cat. J/ApJS/260/1), the most comprehensive
spectroscopic campaign so far to trace the LyC emission of galaxies in
the nearby Universe (z∼0.3). In addition, we include and reanalyze
previous LyC emitters from the studies of Izotov et al.
(2016Natur.529..178I 2016Natur.529..178I, 2016MNRAS.461.3683I 2016MNRAS.461.3683I, 2018MNRAS.474.4514I 2018MNRAS.474.4514I,
2018MNRAS.478.4851I 2018MNRAS.478.4851I, 2021MNRAS.503.1734I 2021MNRAS.503.1734I) and Wang et al.
(2019ApJ...885...57W 2019ApJ...885...57W) as a comparison sample. For all the sources, we
also use ancillary data derived in a homogeneous fashion by the LzLCS
team.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 108 66 UV-SED fits results for the LzLCS sample
tablea2.dat 97 66 Absorption lines results for the LzLCS sample
tablea3.dat 108 23 *UV-SED fits results for the literature sample
tablea4.dat 97 23 *Absorption lines results for the literature sample
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Note on tablea3.dat,tablea4.dat: Izotov et al. (2016Natur.529..178I 2016Natur.529..178I,
2016MNRAS.461.3683I 2016MNRAS.461.3683I, 2018MNRAS.474.4514I 2018MNRAS.474.4514I, 2018MNRAS.478.4851I 2018MNRAS.478.4851I,
2021MNRAS.503.1734I 2021MNRAS.503.1734I) and Wang et al. (2019ApJ...885...57W 2019ApJ...885...57W).
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See also:
J/ApJS/260/1 : Low-redshift Lyman Continuum Survey (LzLCS). I. (Flury+, 2022)
Byte-by-byte Description of file: tablea1.dat tablea3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Object name
16- 25 A10 --- LyCtype Object type (strong, weak or nonleaker)
27- 32 F6.4 --- z Redshift
34- 38 F5.3 mag E(B-V) UV dust-attenuation parameter E(B-V)
40- 44 F5.3 mag e_E(B-V) UV dust-attenuation parameter E(B-V) error
46- 49 F4.2 Myr Age Light-weighted stellar age
51- 54 F4.2 Myr e_Age Light-weighted stellar age error
56- 59 F4.2 Sun Z Light-weighted stellar metallicity
61- 64 F4.2 Sun e_Z Light-weighted stellar metallicity error
66- 67 A2 --- l_fabsesc [≤ ] Limit flag on fabsesc
68- 72 F5.3 --- fabsesc LyC absolute photon escape fraction
74- 78 F5.3 --- E_fabsesc ? Error on fabsesc (upper value)
80- 84 F5.3 --- e_fabsesc ? Error on fabsesc (lower value)
86- 91 F6.2 mag Mint1500 Intrinic dust corrected absolute magnitude
at 1500Å (AB)
93- 96 F4.2 mag e_Mint1500 Intrinic dust corrected absolute magnitude
at 1500Å (AB) error
98-103 F6.2 mag Mobs1500 Observed UV absolute magnitude
at 1500Å (AB)
105-108 F4.2 mag e_Mobs1500 Observed UV absolute magnitude
at 1500Å (AB) error
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Byte-by-byte Description of file: tablea2.dat tablea4.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Object name
16- 25 A10 --- LyCtype Object type (strong, weak or nonleaker)
27- 32 F6.4 --- z Redshift
34- 37 F4.2 0.1nm WHI Weighted-average HI equivalent width
39- 42 F4.2 0.1nm e_WHI Weighted-average HI equivalent width error
44- 48 F5.2 0.1nm WLIS Weighted-average LIS equivalent width
50- 53 F4.2 0.1nm e_WLIS Weighted-average LIS equivalent width error
55- 58 F4.2 --- RHI ?=- Weighted-average HI residual flux (Cf(HI))
60- 63 F4.2 --- e_RHI ?=- Weighted-average HI residual flux error
65- 68 F4.2 --- RLIS ?=- Weighted-average LIS residual flux
(Cf(LIS))
70- 73 F4.2 --- e_RLIS ?=- Weighted-average LIS residual flux error
75- 79 F5.3 --- fabsescHI ?=- Lyman series derived absolute photon
escape fraction
81- 85 F5.3 --- e_fabsescHI ?=- Lyman series derived absolute photon
escape fraction error
87- 91 F5.3 --- fabsescLIS ?=- LIS derived absolute photon
escape fraction
93- 97 F5.3 --- e_fabsescLIS ?=- LIS derived absolute photon
escape fraction error
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Nov-2022