Near-infrared spectroscopy of nearby Seyfert galaxies - II. Molecular content and coronal emission

We present sub-arcsec near-infrared 1.5 - 2.5 micron moderate resolution long-slit spectra of eight nearby Seyfert galaxies (z<0.01), both parallel to the ionization cone and perpendicular to it. These spectra complement similar data on six Seyferts, presented in Reunanen, Kotilainen & Prieto (2002). Large concentrations of molecular gas (H2) are present in the nucleus regardless of the Seyfert type. The spatial extent of the H2 emission is larger perpendicular to the cone than parallel to it in 6/8 (75 %) galaxies, in agreement with the unified models of Active Galactic Nuclei. Broad BrGamma was detected in nearly half of the optically classified Seyfert 2 galaxies, including two objects with no evidence for hidden polarized Broad Line Region. Nuclear [FeII] emission is generally blueshifted which together with high BrGamma/[FeII] ratios suggests shocks as the dominant excitation mechanism in Seyfert galaxies. Bright coronal emission lines [SiVI] and [SiVII] are common in Seyferts, as they are detected in ~60 % of the galaxies. In three galaxies the coronal lines are extended only in the direction parallel to the cone. This could be explained by shock excitation due to the jet or superwind interacting with the interstellar medium.Comment: 19 pages, accepted for publication in MNRA

Origin of the wide-angle hot H2 in DG Tauri: New insight from SINFONI spectro-imaging

We wish to test the origins proposed for the extended hot H2 at 2000K around the atomic jet from the T Tauri star DGTau, in order to constrain the wide-angle wind structure and the possible presence of an MHD disk wind. We present flux calibrated IFS observations in H2 1-0 S(1) obtained with SINFONI/VLT. Thanks to spatial deconvolution by the PSF and to accurate correction for uneven slit illumination, we performed a thorough analysis and modeled the morphology, kinematics, and surface brightness. We also compared our results with studies in [FeII], [OI], and FUV-pumped H2. The limb-brightened H2 emission in the blue lobe is strikingly similar to FUV-pumped H2 imaged 6yr later, confirming that they trace the same hot gas and setting an upper limit of 12km/s on any expansion proper motion. The wide-angle H2 rims are at lower blueshifts than probed by narrow long-slit spectra. We confirm that they extend to larger angle and to lower speed the onion-like velocity structure observed in optical atomic lines. The latter is shown to be steady over more/equal than 4yr but undetected in [FeII] by SINFONI, probably due to strong iron depletion. The H2 rim thickness less/equal than 14AU rules out excitation by C-shocks, and J-shock speeds are constrained to 10km/s. We find that explaining the H2 wide-angle emission with a shocked layer requires either a recent outburst (15yr) into a pre-existing ambient outflow or an excessive wind mass flux. A slow photoevaporative wind from the dense irradiated disk surface and an MHD disk wind heated by ambipolar diffusion seem to be more promising and need to be modeled in more detail

Near-infrared spectroscopy of stellar populations in nearby spiral galaxies

We present high spatial resolution, medium spectral resolution near-infrared (NIR) H- and K-band long-slit spectroscopy for a sample of 29 nearby (z < 0.01) inactive spiral galaxies, to study the composition of their NIR stellar populations. These spectra contain a wealth of diagnostic stellar absorption lines, e.g. MgI 1.575 micron, SiI 1.588 micron, CO (6-3) 1.619 micron, MgI 1.711 micron, NaI 2.207 micron, CaI 2.263 micron and the 12CO and 13CO bandheads longward of 2.29 micron. We use NIR absorption features to study the stellar population and star formation properties of the spiral galaxies along the Hubble sequence, and we produce the first high spatial resolution NIR HK-band template spectra for low redshift spiral galaxies along the Hubble sequence. These templates will find applications in a variety of galaxy studies. The strength of the absorption lines depends on the luminosity and/or temperature of stars and, therefore, spectral indices can be used to trace the stellar population of galaxies. The entire sample testifies that the evolved red stars completely dominate the NIR spectra, and that the hot young star contribution is virtually nonexistent.Comment: 13 pages, 5 figures. Accepted to MNRAS. arXiv admin note: text overlap with arXiv:astro-ph/040313

Multi-wavelength properties of the high-energy bright Seyfert 1 galaxy IGR J18027-1455

A new sample of hard X-ray sources in the Galactic Plane is being revealed by the regular observations performed by the INTEGRAL satellite. The full characterization of these sources is mandatory to understand the hard X-ray sky. Here we report new multifrequency radio, infrared and optical observations of the source IGR J18027-1455, as well as a multi-wavelength study from radio to hard X-rays. The radio counterpart of IGR J18027-1455 is not resolved at any observing frequency. The radio flux density is well fitted by a simple power law with a spectral index alpha=-0.75+/-0.02. This value is typical of optically thin non-thermal synchrotron emission originated in a jet. The NIR and optical spectra show redshifted emission lines with z=0.034, and a broad Halpha line profile with FWHM ~3400 km/s. This suggests an Active Galactic Nucleus (AGN) of type 1 as the optical counterpart of IGR J18027-1455. We confirm the Seyfert 1 nature of the source, which is intrinsically bright at high energies both in absolute terms and when scaled to a normalized 6 cm luminosity. Finally, comparing its X-ray luminosity with isotropic indicators, we find that the source is Compton thin and AGN dominated. This indicates that INTEGRAL might have just seen the tip of the iceberg, and several tens of such sources should be unveiled during the course of its lifetime.Comment: 6 pages, 6 figures. Accepted for publication in A&A. Minor changes according to referee repor

VLT diffraction-limited imaging at 11 and 18 micron of the nearest active galactic nuclei

Mid-infrared imaging at resolutions of 300 mas of the central kpc region of 13 nearby, well-known active galaxies is presented. The bulk of the mid-IR emission is concentrated on an unresolved central source within a size of less than 5 to 130 pc, depending on the object distance. Further resolved emission is detected in 70% of the sample in the form of circumnuclear star-forming rings or diffuse nuclear extended emission. In the three cases with circumnuclear star formation, the stellar contribution is at least as important as that of the AGN. In those with extended nuclear emission -- a third of the sample -- this emission represents a few per cent of the total measured; however, this contribution may be underestimated because of the chopped nature of these observations. This extended emission is generally collimated in a preferential direction often coinciding with that of the extended ionized gas or the jet. In all cases, the nuclear fluxes measured at 11.8 and 18.7 micron represent a minor contribution of the flux levels measured by large aperture IRAS data at the nearest energy bands of 12 and 25 micron. This contribution ranges from 30% to less than 10%. In only three cases do the AGN fluxes agree with IRAS to within a factor of 2. In the AGNs with strong circumnuclear star formation, this component can well account for most of the IRAS flux measured in these objects. But in all other cases, either a low surface brightness component extending over galactic scales or strong extra-nuclear IR sources -- e.g. HII regions in spiral arms -- have to be the main source of the IRAS emission. In either case, the contribution of these components dwarfs that of the AGN at mid-IR wavelengths.Comment: 17 pages, 10 figures. Accepted for publication in MNRA