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Published January 10, 2001 | Published
Journal Article Open

Star Formation History in the NICMOS Northern Hubble Deep Field

Abstract

We present the results of an extensive analysis of the star formation rates determined from the NICMOS deep images of the northern Hubble Deep Field. We use SED template fitting photometric techniques to determine both the redshift and the extinction for each galaxy in our field. Measurement of the individual extinctions provides a correction for star formation hidden by dust obscuration. We determine star formation rates for each galaxy based on the 1500 Å UV flux and add the rates in redshift bins of width 1.0 centered on integer redshift values. We find a rise in the star formation rate from a redshift of 1 to 2 then a falloff from a redshift of 2 to 3. However, within the formal limits of the error bars this could also be interpreted as a constant star formation rate from a redshift of 1 to 3. The star formation rate from a redshift of 3 to 5 is roughly constant followed by a possible drop in the rate at a redshift of 6. The measured star formation rate at a redshift of 6 is approximately equal to the present day star formation rate determined in other work. The high star formation rate measured at a redshift of 2 is due to the presence of two possible ULIRGs in the field. If real, this represents a much higher density of ULIRGs than measured locally. We also develop a new method to correct for faint galaxies or faint parts of galaxies missed by our sensitivity limit, based on the assumption that the star formation intensity distribution function is independent of redshift. We measure the 1.6 μm surface brightness due to discrete sources and predict the 850 μm brightness of all of our galaxies based on the determined extinction. We find that the far-infrared fluxes predicted in this manner are consistent with the lack of detections of 850 μm sources in the deep NICMOS HDF, the measured 850 μm sky brightness due to discrete sources and the ratio of optical-UV sky brightness to far-infrared sky brightness. From this we infer that we are observing a population of sources that contributes significantly to the total star formation rate and these sources are not overwhelmed by the contribution from sources such as the extremely superluminous galaxies represented by the SCUBA detections. We have estimated the errors in the star formation rate due to a variety of sources including photometric errors, the near-degeneracy between reddening and intrinsic spectral energy distribution as well as the effects of sampling errors and large-scale structure. We have tried throughout to give as realistic and conservative an estimate of the errors in our analysis as possible.

Additional Information

© 2001. The American Astronomical Society. Received 2000 May 5; accepted 2000 August 8. This work is supported in part by NASA grant NAG 5-3042. This work utilized observations 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 under NASA contract NAS5-26555. We wish to thank an anonymous referee for suggesting the artificial data test for the partial template extinction degeneracy and for comments that have improved the quality of this work. Two of us (R. I. T. and R. J. W.) wish to acknowledge extremely helpful discussions with David Koo, Alex Szalay, Daniela Calzetti, and David Weinberg. R. I. T. wishes to acknowledge several productive discussions with Ken Lanzetta, Mathias Steinmetz, Mark Dickinson, Neta Bahcall, and Piero Madau. R. J. W. wishes to acknowledge helpful discussions with Ray Carlberg, David Elbaz, and Mauro Giavalisco.

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August 21, 2023
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