J/ApJS/107/1 J/ApJS/107/1 Morphologies of distant galaxies II R G Abraham S Van den Bergh K Glazebrook R S Ellis B X Santiago P Surma R E Griffiths Astrophys. J. Suppl. Ser. 107 1 1996 1996ApJS..107....1A Galaxies, photometry Morphology galaxies: evolution galaxies: fundamental parameters galaxies: interactions surveys The morphological properties of high-redshift galaxies are investigated using a sample of 507 objects (I<22.0mag) from the Hubble Space Telescope (HST) Medium Deep Survey. Independent visual morphological classifications for each galaxy are used to quantify the statistical uncertainties in the galaxy classifications. Visual classifications are found to agree well for I<21mag. Fainter than I=21mag significant disagreements are seen in the independent visual classifications of late-type systems with T>7, merging systems, and peculiar galaxies. The classifications of these systems are shown to be somewhat subjective. Objective classifications based upon measurements of central concentration and asymmetry for the Medium Deep Survey sample are presented. These classifications are calibrated using measurements of structural parameters for an artificially redshifted sample of local objects. Morphologically segregated number counts using both sets of visual classifications and objective classifications support the conclusion that the observed galaxy counts agree with no-evolution predictions for the elliptical and spiral populations, as reported in Glazebrook et al. (1995MNRAS.275L..19G). A major conclusion is that the large overdensity of merging/peculiar/irregular galaxies relative to the predictions of no-evolution models (reported by Glazebrook et al. 1995MNRAS.275L..19G) is confirmed. However, the shape of the faint-end (I>21.0mag) number count relation for peculiar objects is sensitive to the large systematic uncertainties inherent in the visual classification of these objects. Despite this caveat, the frequency of objects showing clear evidence for tidal interactions (e.g., tidal tails) in the HST sample is at least 50% larger than it is among nearby galaxies, at the 2{sigma} level. Relatively few "chain galaxies" are seen among the sample of peculiar objects, suggesting that these systems do not form a large component of the peculiar galaxy population at I<22mag.

HST

ID Identification --- RAh Right ascension (J2000) h RAm Right ascension (J2000) min RAs Right ascension (J2000) s DE- Declination sign --- DEd Declination (J2000) deg DEm Declination (J2000) arcmin DEs Declination (J2000) arcsec Imag I magnitude mag C Central concentration --- A Rotational asymmetry --- RSE Ellis (1990, ASP Conf. vol 10, 248) classification number=1 -2: star -1: compact 0: E 1: E/S0 2: S0 3: Sab 4: S 5: Scdm 6: Ir 7: peculiar 8: merger 9: defect --- n_RSE Note number=2 uem0-38 : Image shows two nuclei and tidal tails. This is clearly an interacting/merging pair uem0-45 : No obvious signs of interaction. uy40-41 : Nucleus too large for Sc classification. uy40-53 : This is not a low surface brightness spiral. uy40-60 : No direct evidence for interactions. ux40-26 : Type Sc assigned because of small nucleus and faint disk. However, no spiral arms are visible ux40-106: Probably S0 rather than Sc because no arms are visible. ubi1-31 : No sign of tidal arms, so probably not a merger. ubi1-64 : Not an image defect. ueh0-10 : Not as compact as an elliptical. ucs0-1 : This appears to be a partly resolved Ir galaxy rather than a merger remnant. uop0-40 : It has a nucleus, so it must be a spiral. uui0-29 : This is an Sa spiral. uui0-38 : This may be a partly resolved Ir galaxy. uui0-51 : Edge-on dwarf irregular. Not an image deSect. uui0-75 : Merger remnant? Has two nuclei and one spiral arm. umd4-76 : Appears to be a low surface brightness dE3. --- VDB van den Bergh (1960ApJ...131..215V & 1960ApJ...131..558V) classification number=1 -2: star -1: compact 0: E 1: E/S0 2: S0 3: Sab 4: S 5: Scdm 6: Ir 7: peculiar 8: merger 9: defect --- Class Classification of van den Bergh (1960PDDO....2..159V) in DDO system --- Com VDB comment --- James Marcout, Patricia Bauer CDS 1997Aug28 UNKNOWN UNKNOWN Prepared via OCR at CDS. J_ApJS_107_1.xml