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High-resolution spectroscopy of a young, low-metallicity optically-thin L = 0.02L* star-forming galaxy at z = 3.12

Vanzella, E., De Barros, S., Cupani, G., Karman, W., Gronke, M., Balestra, I., Coe, D., Mignoli, M., Brusa, M., Calura, F., Caminha, G. -B., Caputi, K., Castellano, M., Christensen, L., Comastri, A., Cristiani, S., Dijkstra, M., Fontana, A., Giallongo, E., Giavalisco, M., Gilli, R., Grazian, A., Grillo, C., Koekemoer, A., Meneghetti, M., Nonino, M., Pentericci, L., Rosati, P., Schaerer, D., Verhamme, A., Vignali, C. & Zamorani, G., 20-Apr-2016, In : Astrophysical Journal Letters. 821, 2, 7 p., 27.

Research output: Contribution to journalArticleAcademicpeer-review

  • E. Vanzella
  • S. De Barros
  • G. Cupani
  • W. Karman
  • M. Gronke
  • I. Balestra
  • D. Coe
  • M. Mignoli
  • M. Brusa
  • F. Calura
  • G. -B. Caminha
  • K. Caputi
  • M. Castellano
  • L. Christensen
  • A. Comastri
  • S. Cristiani
  • M. Dijkstra
  • A. Fontana
  • E. Giallongo
  • M. Giavalisco
  • R. Gilli
  • A. Grazian
  • C. Grillo
  • A. Koekemoer
  • M. Meneghetti
  • M. Nonino
  • L. Pentericci
  • P. Rosati
  • D. Schaerer
  • A. Verhamme
  • C. Vignali
  • G. Zamorani

We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 +/- 0.33 (M-UV = -17.0), low-mass (less than or similar to 10(7)M(circle dot)), and compact (R-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 lowluminosity regimes, in moderately high-resolution spectroscopy (R = lambda/d lambda similar to 3000-7400). We measured C IV lambda 1548, 1550, He II lambda 1640, OIII] lambda 1661, 1666, CIII]lambda lambda 1907, 1909, H beta, [O III] lambda lambda 4959, 5007 emission lines with FWHM less than or similar to 50 km s(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10(-19)-2 x 10(-18) erg s(-1) cm(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Ly alpha emission with Delta v(red -blue) = 280(+/- 7) km s(-1) and delensed fluxes 2.4((blue))vertical bar 8.5((red)) x 10(-18) erg s(-1) cm(-2) (S/N = 38((blue))vertical bar 110((red)) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O III]lambda 5007/[O II] lambda 3727 > 10 ratio. We detect C IV lambda 1548, 1550 resonant doublet in emission, each component with FWHM less than or similar to 45 km s(-1) and redshifted by + 51(+/- 10) km s(-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 +/- 0.20 (F-lambda = lambda(beta)), consistent with a dust-free and young less than or similar to 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-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.

Original languageEnglish
Article number27
Number of pages7
JournalAstrophysical Journal Letters
Volume821
Issue number2
Publication statusPublished - 20-Apr-2016

    Keywords

  • cosmology: observations, galaxies: formation, CLUSTER RXC J2248.7-4431, LYMAN BREAK GALAXIES, LY-ALPHA EMITTERS, SIMILAR-TO 4, ULTRAVIOLET-SPECTRA, COSMIC REIONIZATION, PHYSICAL-PROPERTIES, ABELL S1063, CLASH-VLT, EMISSION

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