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Hα Equivalent Widths from the 3D-HST survey: evolution with redshift and dependence on stellar mass†

Published online by Cambridge University Press:  17 July 2013

Mattia Fumagalli ,
Shannon G. Patel ,
Marijn Franx ,
Gabriel Brammer ,
Pieter van Dokkum ,
Elisabete da Cunha ,
Mariska Kriek ,
Britt Lundgren ,
Ivelina Momcheva  and
Hans-Walter Rix
...Show all authors
Mattia Fumagalli
Affiliation:
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, Netherlands
Shannon G. Patel
Affiliation:
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, Netherlands
Marijn Franx
Affiliation:
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, Netherlands
Gabriel Brammer
Affiliation:
European Southern Observatory, Alonso de Crdova 3107, Casilla 19001, Santiago, Chile
Pieter van Dokkum
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
Elisabete da Cunha
Affiliation:
Max Planck Institute for Astronomy (MPIA), Knigstuhl 17, 69117 Heidelberg, Germany
Mariska Kriek
Affiliation:
Department of Astronomy, University of California, Berkeley, CA 94720, USA
Britt Lundgren
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
Ivelina Momcheva
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
Hans-Walter Rix
Affiliation:
Max Planck Institute for Astronomy (MPIA), Knigstuhl 17, 69117 Heidelberg, Germany
Kasper B. Schmidt
Affiliation:
Max Planck Institute for Astronomy (MPIA), Knigstuhl 17, 69117 Heidelberg, Germany
Rosalind E. Skelton
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
Katherine E. Whitaker
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
Ivo Labbe
Affiliation:
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, Netherlands
Erica Nelson
Affiliation:
Department of Astronomy, Yale University, New Haven, CT 06511, USA
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Abstract

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We investigate the evolution of the Hα equivalent width, EW(Hα), with redshift and its dependence on stellar mass, using the first data from the 3D-HST survey, a large spectroscopic Treasury program with the HST-WFC3. Combining our Hα measurements of 854 galaxies at 0.8<z<1.5 with those of ground based surveys at lower and higher redshift, we can consistently determine the evolution of the EW(Hα) distribution from z=0 to z=2.2. We find that at all masses the characteristic EW(Hα) is decreasing towards the present epoch, and that at each redshift the EW(Hα) is lower for high-mass galaxies. We find EW(Hα) ~ (1+z)1.8 with little mass dependence. Qualitatively, this measurement is a model-independent confirmation of the evolution of star forming galaxies with redshift. A quantitative conversion of EW(Hα) to sSFR (specific star-formation rate) is model dependent, because of differential reddening corrections between the continuum and the Balmer lines. The observed EW(Hα) can be reproduced with the characteristic evolutionary history for galaxies, whose star formation rises with cosmic time to z ~ 2.5 and then decreases to z = 0. This implies that EW(Hα) rises to 400 Å at z = 8. The sSFR evolves faster than EW(Hα), as the mass-to-light ratio also evolves with redshift. We find that the sSFR evolves as (1+z)3.2, nearly independent of mass, consistent with previous reddening insensitive estimates. We confirm previous results that the observed slope of the sSFR-z relation is steeper than the one predicted by models, but models and observations agree in finding little mass dependence.

Keywords

galaxies: evolution galaxies: formation galaxies: high-redshift
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S295: The intriguing life of massive galaxies , August 2012 , pp. 91
Copyright
Copyright © International Astronomical Union 2013 

Footnotes

†

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 12177, 12328

References

† Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 12177, 12328