Galaxy morphology to I = 25 mag in the Hubble Deep Field

Abraham, R.G.; Tanvir, N.R.; Santiago, B.X.; Ellis, R.S.; Glazebrook, K.; van den Bergh, S.

doi:10.1093/mnras/279.3.L47

Galaxy morphology to I = 25 mag in the Hubble Deep Field

Feb, 1996

6 pages

Published in:

Mon.Not.Roy.Astron.Soc. 279 (1996) L47-L52

e-Print:

astro-ph/9602044 [astro-ph]

DOI:

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Abstract: (arXiv)

The morphological properties of galaxies between

21 {\rm~mag} < I < 25 {\rm~mag}

in the {\em Hubble Deep Field} are investigated using a quantitative classification system based on measurements of the central concentration and asymmetry of galaxian light. The class distribution of objects in the {\em Hubble Deep Field} is strongly skewed towards highly asymmetric objects, relative to distributions from both the {\em HST Medium Deep Survey} at

I < 22 {\rm~mag}

and an artificially redshifted sample of local galaxies. The steeply rising number count-magnitude relation for irregular/peculiar/merging systems at

I < 22 {~\rm mag}

reported in Glazebrook \etal\ (1995a) continues to at least

I=25~{\rm mag}

. Although these peculiar systems are predominantly blue at optical wavelengths, a significant fraction also exhibit red

U-B

colours, which may indicate they are at high redshift. Beyond Glazebrook \etal 's magnitude limit the spiral counts appear to rise more steeply than high-normalization no-evolution predictions, whereas those of elliptical/S0 galaxies only slightly exceed such predictions and may turn-over beyond

I \sim 24~{\rm mag}

. These results are compared with those from previous investigations of faint galaxy morphology with HST and the possible implications are briefly discussed. The large fraction of peculiar/irregular/merging systems in the {\em Hubble Deep Field} suggests that by