Stellar population and kinematic properties of ULIRGs and Seyfert galaxies

Team responsible: Valentin D. Ivanov(ESO)
Team members: Juha Reunanen (ESO), Linda Tacconi (MPE), Lowell Tacconi-Garman(ESO)


The goal of this project is to demonstrate the feasibility for observing faint external galaxies with SINFONI/SPIFFI, with and without AO. Two galaxies that cover the extreme (and typical) cases were selected:

(i) NGC7469: Sy1.2, residing in (R')SAB(rs)a host. With bright and point-like nucleus this galaxy allows to demonstrate full AO correction. The H-band data, in together with previously obtained K-band data and IRAM observations, will allow to create a comprehensive dynamical model of the circumnuclear region, and to derive the properties of the central stellar cluster.

(ii) SUPER-ANTENNA: ULIRG, late-stage merger with a Sy2 and a starburst-dominated nuclei. The data will be used to create a velocity field maps from both the CO band head at 2.3 μm, and various emission lines (Brγ at 2.16 μm, H2 at 2.12 μm). The depth of the CO will map the stellar populations across the galaxy. The correlations between the kinematic properties and the stellar populations will be explored.

Target list
NameRA(2000)DEC(2000)Plate-Scale(s)Bands(s)Exp.time(on source)
SUPER-ANTENNA19:31:21.4-72:39:18250 masK3hr
NGC746923:03:15.6+08:52:2625 masH2hr

Programme Description::
This program demonstrates the feasibility of using SINFONI to address two classes of observational problems:

(i) To obtain spectra of external galaxies spatial resolution comparable to that of the HST, with the assistance of the adaptive optics system. Currently this can only be achieved for objects near a bright star, or for bright objects with compact morphology suitable for guiding. Seyfert galaxies, with their compact nuclear point-like sources are typical -- and at the same time -- suitable targets for AO observations. In the future the range of suitable targets will be expanded with the availability of a laser guiding star.

The major scientific drive for AO observations of AGN is to resolve the nuclear regions. There has been a number of studies of the centers of Seyfert galaxies with the HST and with ground-based AO-assisted instruments. SINFONI is the first instrument that offers the possibility to obtain 3-D near-infrared spectroscopy with the resolution of the HST and much higher collecting area.

NGC7469 was selected as a representative of the AGN class, with some previous observations available for comparison. It has a central star clusters and the high-resolution spectroscopy can be used to study the AGN-starburst connection. The Science Verification team plans to obtain H spectra, to be compared with previous long-slit Keck observations, and CO data from the IRAM. The new data are well-suited to constrain the stellar population in the circumnuclear region, because the AO will minimize the contribution of the nuclear point-source.

(ii) To obtain spectra of extended targets under atmospheric seeing, motivated by the necessity to observe many faint objects far from a suitable guiding star. The observers will take advantage of the large field of view of the instrument, to obtain spectra of extended objects.

To verify this mode we have selected Super-Antenna, an ultra-luminous infrared galaxy, and like most ULIRGs. It is a late-stage merger of two systems: Type 2 Seyfert component, and a starburst-dominated component. The central body of Super-Antenna has a diameter of about 1 arcmin but there are extended tails spanning 3-4 arcmin.

The Science Verification team has chosen to observe this galaxy in the K-band, which contains a strong CO feature at 2.3 micron. Our goal is to obtain data for building a velocity map of the system, using the sharp CO bandhead. In addition, we will take a short H-band spectrum, that will help to create reddening maps from the color difference, and to identify any supernova remnants from the Fe e mission at 1.644 μm.

Observing Strategy
The data will be taken with the standard method for the near-infrared observations, obtaining spectra of the target and the sky to carry out the subtraction of the telluric emission. Next, we will observe telluric standards, to correct for the telluric absorption. A more detailed description of the observing strategy will be provided with the reduced data.