J/ApJ/453/48 VI photometry of HST faint field galaxies (Driver+ 1995)
The contribution of late-type/irregulars to the faint galaxy counts from
Hubble Space Telescope Medium Deep Survey images
Driver S.P., Windhorst R.A., Griffiths R.E.
<Astrophys. J. 453, 48 (1995)>
=1995ApJ...453...48D 1995ApJ...453...48D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Morphology
Mission_Name: HST
Keywords: galaxies: evolution - galaxies: fundamental parameters -
galaxies: irregular - galaxies: luminosity function, mass function -
galaxies: statistics - surveys
Abstract:
We present a complete morphologically classified sample of 144 faint
field galaxies from the HST Medium Deep Survey with 20.0=<Imag<22.0mag.
We compare the global properties of the ellipticals and early- and
late-type spirals and find a non-negligible fraction (13/144) of
compact blue [(V-I)<1.0mag] systems with r1/4 profiles. We give the
differential galaxy number counts for ellipticals and early-type
spirals independently and find that the data are consistent with
no-evolution predictions based on conventional flat Schechter
luminosity functions (LFs) and a standard cosmology. Conversely,
late-type/irregulars show a steeply rising differential number count
with slope (δlogN/δm)=0.64±0.1. No-evolution models based
on the Loveday et al. (1992ApJ...390..338L 1992ApJ...390..338L) and Marzke et al.
(1994AJ....108..437M 1994AJ....108..437M & 1994ApJ...428...43M 1994ApJ...428...43M) local luminosity
functions underpredict the late-type/irregular counts by 1.0 and
0.5dex, respectively, at Imag=21.75mag. Examination of the irregulars
alone shows that ∼50% appear inert and the remainder have multiple
cores. If the inert galaxies represent a non-evolving late-type
population, then a Loveday-like LF (α≃-1.0) is ruled out for
these types, and an LF with a steep faint end (α≃-1.5) is
suggested. If multiple core structure indicates recent star formation,
then the observed excess of faint blue field galaxies is likely a
result of et evolutionary processes acting on a steep field LF for
late-type/irregulars. The evolutionary mechanism is unclear, but 60%
of the multiple-core irregulars show close companions. To reconcile a
Marzke-like LF with the faint redshift surveys, this evolution must be
preferentially occurring in the brightest late-type galaxies with
z≥0.5 at mI=21.75mag.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 80 144 A complete catalog of HST field galaxies
obtained from the six MDS fields
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See also:
J/AJ/112/359 : Galaxies in the Hubble Deep Field (van den Bergh+ 1996)
J/AJ/112/1335 : Hubble Deep Field observations (Williams+ 1996)
Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Object identification number
5- 9 A5 --- MDS MDS field name
11 I1 --- WFPC2 WFPC2 CCD number (1=PC, 2, 3, 4=WFC)
13- 17 F5.1 pix Xpos Original X pixel position on the WFPC2 CCD
19- 23 F5.1 pix Ypos Original Y pixel position on the WFPC2 CCD
25- 26 I2 h RAh Right ascension (J2000.0)
28- 29 I2 min RAm Right ascension (J2000.0)
31- 35 F5.2 s RAs Right ascension (J2000.0) (1)
37 A1 --- DE- Declination sign
38- 39 I2 deg DEd Declination (J2000.0)
41- 42 I2 arcmin DEm Declination (J2000.0)
44- 47 F4.1 arcsec DEs Declination (J2000.0) (1)
49- 53 F5.2 mag Imag Total I814 magnitude
55- 58 F4.2 mag V-I Total (V-I) color
60- 64 F5.2 mag/arcsec2 SuBr Central I-band surface brightness within a
radius of 0.2"
66- 70 F5.2 mag (V-I)c Central (V-I) color within a radius of 0.2"
72- 75 F4.2 --- eps Image ellipticity e=1-a/b, computed from the
outermost isophote
77 I1 --- Mtype Galaxy type (2)
79- 80 I2 pix Radius Aperture radius used to determine the I-band
magnitude
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Note (1): Relative RAs and DEs should be accurate to within 0.1".
Absolute WFPC2 astrometry is only accurate to ∼0.5"-1."
Note (2): 0 = E, 1 = 5a, 2 = 5b, 3 = 5c, 4 = 5d, 5 = Irr, 6 = peculiar
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 14-Feb-1997