Details

Autor(en) / Beteiligte

• Vanzella, E
• De Barros, S
• Cupani, G
• Karman, W
• Gronke, M
• Balestra, I
• Coe, D
• Mignoli, M
• Brusa, M
• Calura, F

Titel

HIGH-RESOLUTION SPECTROSCOPY OF A YOUNG, LOW-METALLICITY OPTICALLY THIN L = 0.02L STAR-FORMING GALAXY AT z = 3.12

Ist Teil von

• Astrophysical journal. Letters, 2016-04, Vol.821 (2), p.L27-L27

Ort / Verlag

United States

Erscheinungsjahr

2016

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 + or - 0.33 (M sub(UV)=-17.0, low-mass ([<, ~]10 super(7)M sub([middo t in circle])), and compact (R sub(eff)= 62 pc) freshly star-forming galaxy at z= 3.1169 magnified (16x) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R= [lambda] /d[lambda] ~ 3000-7400). We measured C IV [lambda] 1548, 1550, He II [lambda] 1640, O III][lambda] 1661,1666, C III][lambda][lambda] 1907,1909, H[beta], [OIII][lambda][lambda] 4959,5007 emission lines with [<, ~] 50 km s super(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10 super(-19)-2 x 10 super(-18) erg s super(-1) cm super(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Ly[alpha] emission with [Delta][nu]red - blue) = 280 (+ or -7) km s super(-1) and de-lensed fluxes 2.4 sub((blue)) 8.5 sub((red)) x 10 super(-18) erg s super(-1) cm super(-2)(S/N = 38 sub((blue)) 110 sub((red))) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [OIII][lambda] 5007/ [OII][lambda] 3727 > 10 ratio. We detect C IV [lambda] 1548,1550 resonant doublet in emission, each component with FWHM [<, ~] 45 km s super(-1) and redshifted by +51(+ or -10) km s super(-1) relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV [lambda] 1548,1550 and He II [lambda] 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, [beta] =-2.95 + or - 0.20 (F sub([lambda])= [lambda] super([beta])), consistent with a dust-free and young [<, ~]20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H) < 7.8. We are witnessing an early episode of star formation in which a relatively low N sub(H I) and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space Telescope.