Tuesday, July 16, 2013

1307.3556 (E. Ibar et al.)

Herschel reveals the obscured star formation in HiZELS Hα emitters at z=1.47    [PDF]

E. Ibar, D. Sobral, P. N. Best, R. J. Ivison, I. Smail, V. Arumugam, S. Berta, M. Béthermin, J. Bock, A. Cava, A. Conley, D. Farrah, E. Le Floc'h, D. Lutz, G. Magdis, B. Magnelli, S. Ikarashi, K. Kohno, G. Marsden, S. J. Oliver, M. J. Page, F. Pozzi, L. Riguccini, B. Schulz, N. Seymour, A. J. Smith, M. Symeonidis, L. Wang, J. Wardlow, M. Zemcov
We describe the far-infrared (FIR; rest-frame 8--1000\mu m) properties of a sample of 443 H\alpha-selected star-forming galaxies in the COSMOS and UDS fields detected by the HiZELS imaging survey. Sources are identified using narrow-band filters in combination with broad-band photometry to uniformly select H\alpha\ (and [OII] if available) emitters in a narrow redshift slice at z = 1.47+/-0.02. We use a stacking approach in Spitzer, Herschel (from PEP and HerMES surveys) and AzTEC images to describe their typical FIR properties. We find that HiZELS galaxies with observed H\alpha\ luminosities of ~ 10^{8.1-9.1} Lo have bolometric FIR luminosities of typical LIRGs, L_FIR ~ 10^{11.48+/-0.05} Lo. Combining the H\alpha\ and FIR luminosities, we derive median SFR = 32+/-5 Mo/yr and H\alpha\ extinctions of A(H\alpha) = 1.0+/-0.2 mag. Perhaps surprisingly, little difference is seen in typical HiZELS extinction levels compared to local star-forming galaxies. We confirm previous empirical stellar mass (M*) to A(H\alpha) relations and the little or no evolution up to z = 1.47. For HiZELS galaxies, we provide an empirical parametrisation of the SFR as a function of (u-z)_rest colours and 3.6\mu m photometry. We find that the observed H\alpha\ luminosity is a dominant SFR tracer when (u-z)_rest ~< 0.9 mag or when 3.6\mu m photometry > 22 mag (Vega) or when M* < 10^9.7 Mo. We do not find any correlation between the [OII]/H\alpha\ and FIR luminosity, suggesting that this emission line ratio does not trace the extinction of the most obscured star-forming regions. The luminosity-limited HiZELS sample tends to lie above of the so-called `main sequence' for star-forming galaxies, especially at low M*. This work suggests that obscured star formation is linked to the assembly of M*, with deeper potential wells in massive galaxies providing dense, heavily obscured environments in which stars can form rapidly.
View original: http://arxiv.org/abs/1307.3556

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