J/ApJ/844/171 Lyα profile in 43 Green Pea galaxies (Yang+, 2017)
Lyα profile, dust, and prediction of Lyα escape fraction in Green
Pea galaxies.
Yang H., Malhotra S., Gronke M., Rhoads J.E., Leitherer C., Wofford A.,
Jiang T., Dijkstra M., Tilvi V., Wang J.
<Astrophys. J., 844, 171 (2017)>
=2017ApJ...844..171Y 2017ApJ...844..171Y
ADC_Keywords: Galaxies, spectra ; Redshifts ; Extinction ; Spectra, optical ;
Spectra, ultraviolet ; Equivalent widths
Keywords: dark ages, reionization, first stars; galaxies: dwarf;
galaxies: starburst; radiative transfer; ultraviolet: galaxies
Abstract:
We studied Lyman-α (Lyα) escape in a statistical sample of
43 Green Peas with HST/COS Lyα spectra. Green Peas are nearby
star-forming galaxies with strong [OIII]λ5007 emission lines.
Our sample is four times larger than the previous sample and covers a
much more complete range of Green Pea properties. We found that about
two-thirds of Green Peas are strong Lyα line emitters with
rest-frame Lyα equivalent width >20Å. The Lyα profiles
of Green Peas are diverse. The Lyα escape fraction, defined as
the ratio of observed Lyα flux to intrinsic Lyα flux,
shows anti-correlations with a few Lyα kinematic features-both
the blue peak and red peak velocities, the peak separations, and the
FWHM of the red portion of the Lyα profile. Using properties
measured from Sloan Digital Sky Survey optical spectra, we found many
correlations-the Lyα escape fraction generally increases at
lower dust reddening, lower metallicity, lower stellar mass, and
higher [OIII]/[OII] ratio. We fit their Lyα profiles with the HI
shell radiative transfer model and found that the Lyα escape
fraction is anti-correlated with the best-fit NHI. Finally, we fit
an empirical linear relation to predict fescLyα from the
dust extinction and Lyα red peak velocity. The standard
deviation of this relation is about 0.3dex. This relation can be used
to isolate the effect of intergalactic medium (IGM) scatterings from
Lyα escape and to probe the IGM optical depth along the line of
sight of each z>7 Lyα emission-line galaxy in the James Webb
Space Telescope era.
Description:
In SDSS DR7, a sample of 251 Green Peas was observed as serendipitous
spectroscopic targets (Cardamone+ 2009MNRAS.399.1191C 2009MNRAS.399.1191C). A subset of 66
Green Peas have sufficient signal-to-noise ratio (S/N) in both
continuum and emission lines (Hα, Hβ, and [OIII]λ5007)
to study galactic properties. In Paper I (Yang+ 2016ApJ...820..130Y 2016ApJ...820..130Y),
we matched these 66 Green Peas with the COS archive and studied
Lyα escape in a sample of 12 Green Peas with COS UV spectra.
To address the bias and expand the sample size, we took the Lyα
spectra of 20 additional Green Peas (PI S. Malhotra, GO 14201).
We also supplement this sample with 11 additional Green Peas from
published literature. In total, we have 43 Green Peas from six HST
programs -- 20 galaxies from GO 14201 (PI S. Malhotra), 9 galaxies
from GO 12928 (PI A. Henry; Henry+ 2015ApJ...809...19H 2015ApJ...809...19H), 7 galaxies
from GO 11727 and GO 13017 (PI T. Heckman; Heckman+ 2011ApJ...730....5H 2011ApJ...730....5H ;
Alexandroff+ 2015ApJ...810..104A 2015ApJ...810..104A), 2 galaxies from
GO 13293 (PI A. Jaskot; Jaskot & Oey 2014ApJ...791L..19J 2014ApJ...791L..19J), and 5
galaxies from GO 13744 (PI T. Thuan; Izotov+ 2016MNRAS.461.3683I 2016MNRAS.461.3683I).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . this file
table1.dat 81 43 The Green Peas sample
table2.dat 69 43 The line measurements from SDSS spectra
table3.dat 64 43 Lyα properties
table4.dat 73 23 Lyα profile model parameters
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/ApJ/642/L13 : ECDFS MUSYC galaxies UBVRIzNB5000 photometry (Gawiser+, 2006)
J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)
J/ApJ/680/1072 : Lyα-emitting galaxies at 0.2<z<0.35 (Deharveng+, 2008)
J/ApJ/706/762 : LAEs at z∼4.5 in the LALA Cetus field (Wang+, 2009)
J/ApJ/711/928 : Low-redshift Lyα galaxies from GALEX (Cowie+, 2010)
J/ApJ/738/136 : LAEs between 0.19<z<1.25 with GALEX grism (Cowie+, 2011)
J/A+A/531/A12 : Grid of Lya radiation transfer models (Schaerer+, 2011)
J/A+A/561/A89 : Optical spectroscopy of 24 Ly-alpha emitters (Atek+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name (HHMM+DDMM; J2000)
11- 12 I2 h RAh Hour of Right Ascension (J2000)
14- 15 I2 min RAm Minute of Right Ascension (J2000)
17- 21 F5.2 s RAs Second of Right Ascension (J2000)
23- 23 A1 --- DE- Sign of the Declination (J2000)
25- 26 I2 deg DEd Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of Declination (J2000)
36- 42 F7.5 --- zsp [0.09/0.4] Redshift, from SDSS
optical spectra
44- 48 F5.3 mag E(B-V)MW [0.007/0.09] Milky Way extinction,
Schlafly & Finkbeiner
(2011ApJ...737..103S 2011ApJ...737..103S)
50- 54 F5.3 mag E(B-V) [0/0.5] Dust extinction
56- 59 F4.2 --- 12+log(O/H) [7.7/8.4] Gas metallicity, 12+log(O/H)
61- 64 F4.2 [Msun] logM [7.8/10] Stellar mass
66- 70 F5.2 Msun/yr SFR [1.3/62.4] Star formation rate,
from Hα luminosity
72- 75 F4.2 kpc Re [0.3/1.5] Half light radius
77- 81 I5 --- PID HST/COS program identifier
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name (HHMM+DDMM; J2000)
11- 14 I4 10-20W/m2 [OII]3727 [73/5172] Flux, [OII]3727
16- 17 I2 10-20W/m2 e_[OII]3727 [3/29] Error, [OII]3727
19- 23 F5.1 10-20W/m2 [OIII]4363 [4/153] Flux, [OIII]4363
25- 27 F3.1 10-20W/m2 e_[OIII]4363 [0.8/7] Error, [OIII]4363
29- 32 I4 10-20W/m2 Hbeta [58/2909] Flux, Hbeta
34- 35 I2 10-20W/m2 e_Hbeta [2/15] Error, Hbeta
37- 40 I4 10-20W/m2 [OIII]4959 [123/4275] Flux, [OIII]4959
42- 43 I2 10-20W/m2 e_[OIII]4959 [1/15] Error, [OIII]4959
45- 49 I5 10-20W/m2 [OIII]5007 [371/12949] Flux, [OIII]5007
51- 52 I2 10-20W/m2 e_[OIII]5007 [4/46] Error, [OIII]5007
54- 57 I4 10-20W/m2 Halpha [78/8855] Flux, Halpha
59- 60 I2 10-20W/m2 e_Halpha [4/57] Error, Halpha
62- 64 I3 0.1nm EW(Ha) [232/921] Restframe equivalent width,
Halpha
66- 69 F4.1 --- [OIII]/[OII] [1.5/14.2] Extinction corrected
[OIII]/[OII] ratio (1)
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Note (1): Corrected using the Calzetti+ (2000ApJ...533..682C 2000ApJ...533..682C) extinction law.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name (HHMM+DDMM; J2000)
11- 16 F6.1 10-19W/m2 Flux(LyA) [-1.4/1524]? Flux, Lyman-alpha
18- 20 F3.1 10-19W/m2 e_Flux(LyA) [0.6/10]? Error, LyA flux
22- 25 F4.1 [10-7W] logL(LyA) [41/43.2]? log luminosity, LyA,
in erg/s unit
27- 31 F5.1 0.1nm EW(LyA) [3/165]? rest-frame equivalent
width of LyA
33- 37 F5.3 --- fesc(LyA) [0.005/1.2]? LyA escape fraction
39- 42 I4 km/s V(blue-pk) [-427/-56]? Velocity of LyA blue-peak
44- 45 I2 km/s e_V(blue-pk) [13/88]? Error, V(blue-pk)
47- 49 I3 km/s V(red-pk) [67/568]? Velocity of LyA red-peak
51- 52 I2 km/s e_V(red-pk) [10/94]? Error, V(red-pk)
54- 56 I3 km/s FWHM(red) [160/435]? FWHM of the red portion of
LyA profile
58- 60 I3 km/s e_FWHM(red) [15/150]? Error, FWHM(red)
62- 64 A3 --- Notes Note(s) on Lyα (2)
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Note (2): Flag as follows:
a = These are confirmed LyC leakers from Izotov et al. (2016MNRAS.461.3683I 2016MNRAS.461.3683I).
b = Their Lyα profiles do not have blue peaks.
c = Their Lyα profiles are too noisy for measuring Lyα kinematic
features.
d = These Green Peas show damped Lyα absorption wings in their Lyα
spectra.
e = No Lyα emission line was detected.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name (HHMM+DDMM; J2000)
11- 15 F5.2 [cm-2] logNHI [16/21] HI column density of the outflowing
HI shell
17- 20 F4.2 [cm-2] e_logNHI [0.07/2] Negative uncertainty on logNHI
22- 25 F4.2 [cm-2] E_logNHI [0.07/1.6] Positive uncertainty on logNHI
27- 30 I4 km/s Vexp [-171/270] Outflowing velocity of the HI shell
32- 33 I2 km/s e_Vexp [1/26] Negative uncertainty on Vexp
35- 36 I2 km/s E_Vexp [1/44] Positive uncertainty on Vexp
38- 40 F3.1 [K] logT [3/5.7] Log of HI gas temperature (1)
42- 44 F3.1 [K] e_logT [0.1/1.3] Negative uncertainty on logT
46- 48 F3.1 [K] E_logT [0.1/0.6] Positive uncertainty on logT
50- 53 F4.2 --- tau [0/4.9] Dust optical depth
55- 58 F4.2 --- e_tau [0/0.4] Negative uncertainty on tau
60- 63 F4.2 --- E_tau [0/1.2] Positive uncertainty on tau
65- 67 I3 km/s sigma [64/427] 1σ width of the Gaussian
profile of the intrinsic Lyα line
69- 70 I2 km/s e_sigma [2/29] Negative uncertainty on sigma
72- 73 I2 km/s E_sigma [2/31] Positive uncertainty on sigma
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Note (1): HI gas temperature including turbulent motion as well as the true
temperature.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Mar-2018