[107.06] HST Imaging in the Chandra Deep Field South: III. Quantitative Morphology of the 1 Msec Chandra Counterparts and Comparison with the Field Population

AAS 201st Meeting, January, 2003
Session 107. AGN
Oral, Wednesday, January 8, 2003, 2:00-3:30pm, 616-617

[107.06] HST Imaging in the Chandra Deep Field South: III. Quantitative Morphology of the 1 Msec Chandra Counterparts and Comparison with the Field Population

N. A. Grogin (JHU), A. M. Koekemoer, E. J. Schreier (STScI), Chandra Deep Field South GTO Team

We present a quantitative morphological analysis of the 37 HST/WFPC2 counterparts we identified (Koekemoer et al. 2002) in the 1 Msec Chandra Deep Field South (CDFS). We investigate: 1) 1-D surface brightness profiles from isophotal ellipse fitting; 2) 2-D, PSF-convolved, bulge+disk+nucleus profile-fitting to determine the optical flux from the central engine alone; 3) asymmetry and concentration indices for all ~3000 sources in our three WFPC2 pointings to look for systematic bias in these shape parameters for the CDFS counterparts; and 4) near-neighbor galaxy counts to compare the local environments of the X-ray sources versus the field control sample.

Our 2-D profile fitting reveals a significant nuclear point-source component in ~1/2 of the resolved HST/WFPC2 counterparts. This fraction is comparable for analogous low-redshift samples of moderate-luminosity AGN, suggesting no evidence for evolution in their optical obscuration out to z~0.5-1, typical of our sources. The nuclear components of the resolved CDFS sources exhibit a narrow range of F_X/F_opt,nuc which is consistent with the several HST-unresolved X-ray sources in our fields.

The asymmetry index distribution of the 21 CDFS sources at I<23 is indistinguishable from the I<23 field. Similar findings for local AGN samples suggest no close connection between galaxy mergers and AGN activity - our results extend this counterargument to z~0.5-1. Moreover, the frequency of I<23 near neighbors around the CDFS counterparts is not significantly different from the field sample.

By contrast, the concentration indices for the CDFS counterparts are clearly skewed towards larger values - inconsistent with the field distribution at 5-sigma. A plausible inference is that the strong correlation between black hole mass and host galaxy concentration index observed in nearby galaxies is already evident by z~0.5-1.

We also highlight preliminary results from the successor ACS GOODS morphological analyses of the same field.

The author(s) of this abstract have provided an email address for comments about the abstract: mailto:nagrogin@pha.jhu.edu

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