Multi-Object Near-IR H-alpha Spectroscopy of z~1 star-forming galaxies in the HDF-N

Abstract

We present preliminary results from a programme to obtain multi-object near-infrared spectroscopy of galaxies at redshifts $0.7<z<1.5$. We are using the instrument CIRPASS (the Cambridge Infra-Red PAnoramic Survey Spectrograph), in multi-object mode, to survey H-alpha in galaxies at $z\sim 1$. We aim to address the true star formation history of the universe at this epoch: potentially the peak period of star formation activity. H-alpha is the same star formation measure used at low redshift, and hence we can trace star formation without the systematic uncertainties of using different calibrators in different redshift bins, or the extreme dust extinction in the rest-UV. CIRPASS has been successfully demonstrated in multi-object mode on the AAT and WHT. Here we present preliminary results from one of our fields, the Hubble Deep Field North, observed with the WHT. With 150 fibres deployed over an unvignetted field of $\sim 15$arcmin, we have several detections of H-alpha from star forming galaxies at $0.8<z<1.0$ and present spectra of the seven brightest of these. By pre-selecting galaxies with redshifts such that H-alpha will appear between the OH sky lines, we can detect star formation rates of $5h_{70}^{-2}{M}_{\odot }{\mathrm{yr}}^{-1}$ ($5\sigma$ in 3-hours, ${\Omega }_M=0.3$, ${\Omega }_{\Lambda }=0.7$). It appears that star formation rates inferred from H-alpha are, on average, a factor of more than two higher than those based on the UV continuum alone.

arXiv comment6 pages, 3 figures, accepted for publication in MNRAS Letters

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• VLT and ACS observations of RDCS J1252.9-2927: dynamical structure and galaxy populations in a massive cluster at z=1.237
• Science Programs for a 2 m-class Telescope at Dome C, Antarctica: PILOT, the Pathfinder for an International Large Optical Telescope
• Cosmic Star Formation Activity at z=2.2 Probed by H-alpha Emission Line Galaxies
• Integral-field spectroscopy of Centaurus A nucleus
• The star formation rate at redshift one: H-alpha spectroscopy with CIRPASS
• Probing nuclear activity versus star formation at z~0.8 using near-infrared multi-object spectroscopy