Caltech Faint Galaxy Redshift Survey XIII : Spectral Energy Distributions for Galaxies in the Region of the Hubble Deep Field North 1 Judith

We introduce a new empirical function for modeling the spectral energy distributions of galaxies. We apply it to a sample of 590 galaxies in the region of the HDF with z < 1.5 using multi-color photometry with wide wavelength coverage combined with spectroscopic redshifts from our 93% complete R-selected redshift survey there. We find the following: • As expected, galaxies with strong signs of recent star formation (i.e. those which show emission lines) have bluer continua in both the rest frame UV and the optical/near-infrared. • The redder galaxies tend to be more luminous. Although galaxies with strong absorption lines and no emission features are ∼15% of the total sample with 0.25 < z < 0.8, they are ∼50% of the 25 most luminous galaxies in the sample at rest-frame R. • The SEDs of actively star forming galaxies become bluer in the mean in the rest-frame UV at higher redshift, which trend might arise from SED modeling errors. Aside from this, we discern no change with redshift in the relationship between SED characteristics and galaxy spectral type based on the strength of narrow emission and absorption features. • Combining with similar work at higher and lower redshift, the bluest galaxies have indistinguishable spectral energy distributions in the rest frame ultraviolet over the redshift regime 0 to 3. • There is no evidence in our R-selected sample that supports the existence of a substantial population of very dusty star forming galaxies at z ∼< 1.5. • Our ability to predict the mid-IR flux using the UV/optical/near-IR SEDs is limited. • The potential accuracy of photometric redshifts, bearing in mind that a break at 4000Å must be detectable to within the errors of the photometry to assign a photo-z for galaxies in this redshift regime, is evaluated. Based in large part on observations obtained at the W.M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California and the NASA, Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, CA 91125