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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
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). 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), 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), 7 galaxies from GO 11727 and GO 13017 (PI T. Heckman; Heckman+ 2011ApJ...730....5H ; Alexandroff+ 2015ApJ...810..104A), 2 galaxies from GO 13293 (PI A. Jaskot; Jaskot & Oey 2014ApJ...791L..19J), and 5 galaxies from GO 13744 (PI T. Thuan; Izotov+ 2016MNRAS.461.3683I). File Summary:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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 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) 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
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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)
Note (1): Corrected using the Calzetti+ (2000ApJ...533..682C) extinction law.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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)
Note (2): Flag as follows: a = These are confirmed LyC leakers from Izotov et al. (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.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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
Note (1): HI gas temperature including turbulent motion as well as the true temperature.
History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Mar-2018
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