Home List of Titles Morphological number counts and redshift distributions to I < 26 from the Hubble Deep Field: implications for the evolution of ellipticals, spirals, and irregulars
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/210186
- Morphological number counts and redshift distributions to I < 26 from the Hubble Deep Field: implications for the evolution of ellipticals, spirals, and irregulars
- Driver, S. P.; Fernandez-Soto, A.; Couch, W. J.; Odewahn, S. C.; Windhorst, R. A.; Phillipps, S.; Lanzetta, K.; Yahil, A.
- We combine the photometric redshift data of Fernandez-Soto et al. with the morphological data of Odewahn et al. for all galaxies with I<26.0 detected in the Hubble Deep Field. From this combined catalog we generate the morphological galaxy number counts and corresponding redshift distributions and compare these to the predictions of high-normalization zero- and passive-evolution models. From this comparison we conclude the following: 1. E/S0's are seen in numbers and over a redshift range consistent with zero-evolution or minimal passive-evolution to I=24. Beyond this limit, fewer E/S0's are observed than predicted implying a net negative evolutionary process—luminosity dimming, disassembly or masking by dust—at I>24. The breadth of the redshift distribution at faint magnitudes implies strong clustering or an extended epoch of formation commencing at z>3. 2. Spiral galaxies are present in numbers consistent with zero-evolution predictions to I=22. Beyond this magnitude some net positive evolution is required. Although the number counts are consistent with the passive-evolution predictions to I=26.0, the redshift distributions favor number and luminosity evolution, although few obvious mergers are seen (possibly classified as irregulars). We note that beyond z~2 very few ordered spirals are seen suggesting a formation epoch of spiral galaxies at z~1.5-2. 3. There is no obvious explanation for the late-type/irregular class, and this category requires further subdivision. While a small fraction of the population lies at low redshift (i.e., true irregulars), the majority lie at redshifts 1
1.5 mergers are frequent and, taken in conjunction with the absence of normal spirals at z>2, the logical inference is that they represent the progenitors of normal spirals that form via hierarchical merging.
- Publication type
- Journal article
- The Astrophysical Journal Letters, Vol. 496, no. 2 (Apr 1998), pp. L93-L96
- Publication year
- FOR Code(s)
- 0201 Astronomical and Space Sciences; 0305 Organic Chemistry; 0306 Physical Chemistry (Incl. Structural)
- Galaxies: elliptical and lenticular, cD; Galaxies: evolution; Galaxies: irregular; Galaxies: spiral
- University of Chicago Press
- Publisher URL
- Copyright © 1998 The American Astronomical Society. All rights reserved.
- Peer reviewed