J/MNRAS/477/2817 Luminous Lyα emitters at z∼2-3 (Sobral+, 2018)
The nature of luminous Lyα emitters at z ∼ 2-3:
maximal dust-poor starbursts and highly ionizing AGN.
Sobral D., Matthee J., Darvish B., Smail I., Best P.N., Alegre L.,
Rottgering H., Mobasher B., Paulino-Afonso A., Stroe A., Oteo I.
<Mon. Not. R. Astron. Soc., 477, 2817-2840 (2018)>
=2018MNRAS.477.2817S 2018MNRAS.477.2817S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Ultraviolet ; Redshifts ; Photometry ;
Equivalent widths
Keywords: galaxies: active - galaxies: evolution - galaxies: high-redshift -
galaxies: ISM - galaxies: starburst - cosmology: observations
Abstract:
Deep narrow-band surveys have revealed a large population of faint
Lyα emitters (LAEs) in the distant Universe, but relatively
little is known about the most luminous sources
(LLya≳1042.7erg/s; LLya≳L*^Lya). Here we present the
spectroscopic follow-up of 21 luminous LAEs at z∼2-3 found with
panoramic narrow-band surveys over five independent extragalactic
fields (≃4x106Mpc3 surveyed at z∼2.2 and z∼3.1). We use WHT/ISIS,
Keck/DEIMOS, and VLT/X-SHOOTER to study these sources using high
ionization UV lines. Luminous LAEs at z∼2-3 have blue UV slopes
(β=-2.0+0.3-0.1) and high Lyα escape fractions
(50+20-15 per cent) and span five orders of magnitude in UV
luminosity (MUV≃-19 to -24). Many (70 per cent) show at least one
high ionization rest-frame UV line such as CIV, NV, CIII], HeII or
OIII], typically blue-shifted by ≃100-200km/s relative to Lyα.
Their Lyα profiles reveal a wide variety of shapes, including
significant blue-shifted components and widths from 200 to 4000km/s.
Overall, 60±11 per cent appear to be active galactic nucleus (AGN)
dominated, and at LLya>1043.3erg/s and/or MUV←21.5 virtually
all LAEs are AGNs with high ionization parameters (logU=0.6±0.5) and
with metallicities of ≃0.5-1Z☉. Those lacking signatures of
AGNs (40±11 per cent) have lower ionization parameters
(logU=-3.0+1.6-0.9 and logξion=25.4±0.2) and are apparently
metal-poor sources likely powered by young, dust-poor 'maximal'
starbursts. Our results show that luminous LAEs at z∼2-3 are a diverse
population and that 2xL*Lya and 2*MUV* mark a sharp transition
in the nature of LAEs, from star formation dominated to AGN dominated.
Description:
Our luminous LAEs are selected from wide-field narrow-band Lyα
surveys. Candidate bright LAEs at z∼2.2 are selected from the
1.43deg2 CALYMHA survey (EW0>5Å, covering the UDS and COSMOS
fields).
We used the Intermediate dispersion Spectrograph and Imaging System
(ISIS) on the William Herschel Telescope (WHT) to observe
z∼2-3Lyα candidates. ISIS is a double-armed, medium-resolution
spectrograph, which allows simultaneous observing with the blue and
red arms.
DEIMOS was used to spectroscopically target eight luminous Lyα
candidates at z∼3 in five different masks for the Bootes field, and
in one mask for GOODS-N over three different nights in 2016 June 2,
July 6, and July 29.
We used X-SHOOTER (Vernet et al. 2011) to observe 11 candidate
luminous z=2.2-3.1 LAEs in 2016 October, 2017 January, June-July,
December, and 2018 January .
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 296 21 Our spectroscopic sample of luminous LAEs, ranked
by redshift and then by Lyα luminosity of
the parent sample
sp/* . 21 Individual spectra
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- ID Name (IDSMDPaper_final)
15- 16 I2 h RAh Right ascension (J2000)
18- 19 I2 min RAm Right ascension (J2000)
21- 25 F5.2 s RAs Right ascension (J2000)
27 A1 --- DE- Declination sign (J2000)
28- 29 I2 deg DEd Declination (J2000)
31- 32 I2 arcmin DEm Declination (J2000)
34- 37 F4.1 arcsec DEs Declination (J2000)
39- 45 F7.5 --- zspLya ?=- Lyα spectroscopic redshift
(zspecLya)
47- 54 F8.6 --- E_zspLya ?=- Error on zspLya (upper value)
(zspecLya_up)
56- 63 F8.6 --- e_zspLya ?=- Error on zspLya (lower value)
(zspecLya_down)
65- 72 F8.4 mag MUV Absolute UV magnitude (AB) (MUV)
74- 80 F7.5 mag E_MUV Error on MUV (upper value) (MUVerrup)
82- 88 F7.5 mag e_MUV Error on MUV (lower value) (MUVerrdown)
90- 97 F8.5 --- beta Rest frame UV beta slope
(flambda∝lambdabeta) (Beta)
99-106 F8.6 --- E_beta Error on beta (upper value) (Betaerrup)
108-115 F8.6 --- e_beta Error on beta (lower value) (Betaerrdown)
117-124 A8 --- Class Classification (Table_flag)
126-132 F7.4 mag NBAp2 Narrow-band magnitude (NB_AP2)
134-140 F7.5 mag e_NBAp2 rms uncertainty on NBAP2 (NBERRAP2)
142-148 F7.4 mag BBAp2 Broad-band magnitude (BB_AP2)
150-156 F7.5 mag e_BBAp2 rms uncertainty on BBAP2 (BBERRAP2)
158-169 E12.6 --- lineflux Line flux (lineflux)
171-182 E12.6 --- E_lineflux Error on lineflux (upper value)
(linefluxerrup)
184-195 E12.6 --- e_lineflux Error on lineflux (lower value)
(linefluxerrdown)
197-204 F8.4 0.1nm EW0 Equivalent width (EW_0)
206-214 F9.5 0.1nm E_EW0 Error on EW0 (upper value) (EW0err_up)
216-224 F9.5 0.1nm e_EW0 Error on EW0 (lower value) (EW0err_down)
226-232 F7.4 [10-7W] logLLya Lyα luminosity (Lya_lum)
234-240 F7.5 [10-7W] E_logLLya Error on EW0 (upper value) (Lyalumerr_up)
242-248 F7.5 [10-7W] e_logLLya Error on EW0 (lower value) (Lyalumerr_down)
250-257 F8.3 km/s FWHMLya ?=- Lyα FWHM (FWHM_Lya)
259-266 F8.4 km/s E_FWHMLya ?=- Error on FWHMLya (upper value)
(FWHMLyaup)
268-275 F8.4 km/s e_FWHMLya ?=- Error on FWHMLya (lower value)
(FWHMLyadown)
277-296 A20 --- FileName Name of the spectrum file in subdirectory sp
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.2 0.1nm lambda Observed wavelength vacuum
10- 21 E12.6 10mW/m2 Flux ?=- Observed flux (erg/s/cm2/AA
23- 34 E12.6 10mW/m2 e_Flux ?=- Error on observed flux
36- 38 F3.1 --- Flag [0/1] OH Sky line flag
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Jun-2021