NIR host galaxy properties of the most luminous X-ray AGN at 0.04 < z < 1

Team responsible: J.-U. Pott (ESO, Uni Cologne)
Team members: J. Zuther (Uni Cologne, MPE), A. Glindemann (ESO), A. Eckart (Uni Cologne), C. Iserlohe (Uni Cologne), A. Krabbe (Uni Cologne), W. Voges (MPE)

Project README
Finding Charts: K-bandoptical
Target visibility: AugustOctober

Recent X-ray surveys have now resolved most of the X-ray background (XRB) into discrete sources. The most X-ray luminous AGN (L0.5-2kev > 1043 - 1046 erg/s) cannot be studied locally (z < 0.015) on a statistical basis. In order to understand the nature of these bright X-ray AGN at intermediate redshift, we propose deep JHK spectroscopy using SINFONI with and without adaptive optics for Mrk 609. This active galaxy is an exemplary target of an 80 galaxy sample. It has been recently defined to enable a series of AO observations, necessary to investigate the associated host galaxies properties systematically.
SINFONI data will allow us to estimate black hole masses using stellar absorption features (like CO(2-0), CO(6-3), SiI), investigate the circum-/nuclear excitation (H-recombination lines, [SiVI], H2), determine the presence and importance of nuclear bars and/or circum-nuclear star forming rings, derive the amount/distribution of extinction and the intrinsic host luminosity in this object

Target list
NameRA(2000)DEC(2000)Plate-Scale(s)Bands(s)Exp.time(on source)
Mrk 60903:25:25.3-06:08:37.9100, 250H+K/K, Jsee README

Science Objectives
A breakthrough in the understanding of the XRB was accomplished by its resolution into individual sources. A large majority of the optical counterparts in the ROSAT deep surveys turns out to be AGN. Silverman et al. (2004) showed, that the most X-ray luminous (L0.5-2keV > 1043 - 1046 erg/s) of these objets are extremly rare within the local cosmological volume (z < 0.015). The astrophysical nature of these important sources still remains mysterious. The host properties of this class of AGN (Zuther at el. 2004) has to be studied and compared to those of the optically and infrared selected QSOs (McLeod & Rieke 1995, Bahcall et al. 1997, Dunlop et al. 2003), ULIRGS (Tacconi et al. 2003), and ellipticals composing the fundamental plane (e.g. Kormendy &Djorgovskis 1989). Thus the proposed program fulfills two major criteria of the Science Verification at the same time. On the one hand the lower NIR brightnesses are challenging the SINFONI system capabilities and the feasibility of SINFONI observations of similar targets can be studied. In addition the exemplary target Mrk 609 (see above) can be observed with both on- and off-axis AO, using a nearby Guide Star.

On the other hand the scientific outcome of the observations will be of wide interest, because similar NIR observations could not be conducted before. Further the availability of X-ray and optical data of these targets expands the possibilities of the interpretation of the SINFONI data. An important question is whether hard X-ray spectra are hardened due to a large amount of intrinsic absorption or whether the spectrum of the central engine is intrinsically hard. While population models predict that extinction is a key factor, some of the relevant radiation mechanisms can produce intrinsic spectra of the required observed hardness. It has to be determined how the nuclear properties are correlated with the properties of the corresponding hosts.

Aspects of the scientific analysis of the SINFONI SV data to study the NIR host galaxy properties are: *) The 1.589 μm[SiI] and 1.63 μm CO(6-3) absorption line features will be complemented with information on hydrogen lines and continuum colors to discuss implications for star formation.
*) The spectral resolution of about 100 km/s will allow to precisely measure line fluxes, stellar dynamics, and emission line widths, which can be used to estimate black-hole and host masses (e.g. Green et al. 2004).
*) The effect of the intense UV/X-ray radiation on the nuclear and bulge environment can be studied with hydrogen recombination lines, Fe-lines, and the 1.9615 μm [SiVI] coronal line. Extended fluorescent H2 line emission may arise by nuclear radiation fields or extended massive star formation. These effects have not yet been analyzed for the closest luminous X-ray AGN.
*) What is the detailed structure of the host galaxies? How dominant are the bulges? Are these X-ray luminous galaxies located in 2-3 L* hosts - as most luminous AGN - of in L* or even sub-L* hosts? The angular resolution of SINFONI is needed to clearly separate the nucleus from the central bulge.
*) The JHK host colors will allow us to determine the amount and distribution of extinction and the contribution of warm/hot dust to the NIR emission. NIR colors are more sensitive to higher amounts of extinction and can be obtained at 0.1" resolution. In addition the colors provide important complementary information for stellar population synthesis.

Observation Strategy
The table in README lists the different observation blocks, needed to get a complete NIR data set. Due to the lower target brightness, the 100 mas/pix scale is requested, if the AO loop can be closed.

The pre-imaging in H+K and J band is needed to select the correct exposure times and spectral bands for the long integration blocks. In bad weather conditions, hampering the AO system, seeing-limited observations with 250 mas/pix will also provide interesting data. In addition to their own scientific content, e.g. these data can be directly complemented with SDSS optical spectroscopy / imaging data.

Details on the observing strategy as well as calibration aspects are described in the README file.