Spatially Resolved Near-Infrared Spectroscopy of Seyfert 2 Galaxies Mk 1066, NGC 2110, NGC 4388, and Mk 3

We present near-infrared spectra with resolutions of lambda/dlambda~1200 in the emission lines of Pa-beta, [FeII] (1.2567um), Br-gamma, and H2 v=1-0S(1) of the nuclei and circumnuclear regions of the four Seyfert 2 galaxies Mk 1066, NGC 2110, NGC 4388, and Mk 3. All of these galaxies show strong near-infrared line emission that is detected at radii several times the spatial resolution, corresponding to projected physical scales of 0.07 to 0.7 kpc. Velocity gradients are detected in these nuclei, as are spatial variations in line profiles and flux ratios. We compare the spatial and velocity distribution of the line emission to previously observed optical line and radio emission. The evidence indicates that the [FeII] emission is associated with the Seyfert activity in the galaxies. Our data are consistent with X-ray heating being responsible for most of the [FeII] emission, although differences in [FeII] and Pa-beta line profiles associated with radio emission suggests that the [FeII] emission is enhanced by fast shocks associated with radio outflows. The H2 emission is not as strongly associated with outflows or ionization cones as is the emission in other lines, but rather appears to be primarily associated with the disk of the galaxy.Comment: 35 pages, 24 figure

The nature and evolution of Ultraluminous Infrared Galaxies: A mid-infrared spectroscopic survey

We report the first results of a low resolution mid-infrared spectroscopic survey of an unbiased, far-infrared selected sample of 60 ultraluminous infrared galaxies, using ISOPHOT-S on board ISO. We use the ratio of the 7.7um `PAH' emission feature to the local continuum as a discriminator between starburst and AGN activity. About 80% of all the ULIRGs are found to be predominantly powered by star formation but the fraction of AGN powered objects increases with luminosity. Observed ratios of the PAH features in ULIRGs differ slightly from those in lower luminosity starbursts. This can be plausibly explained by the higher extinction and/or different physical conditions in the interstellar medium of ULIRGs. The PAH feature-to-continuum ratio is anticorrelated with the ratio of feature-free 5.9um continuum to the IRAS 60um continuum, confirming suggestions that strong mid-IR continuum is a prime AGN signature. The location of starburst-dominated ULIRGs in such a diagram is consistent with previous ISO-SWS spectroscopy which implies significant extinction even in the mid-infrared. We have searched for indications that ULIRGs which are advanced mergers might be more AGN-like, as postulated by the classical evolutionary scenario. No such trend has been found amongst those objects for which near infrared images are available to assess their likely merger status.Comment: aastex, 4 eps figures. Revised version, accepted by ApJ (Letters

On measuring the Tully-Fisher relation at z>1z > 1

The evolution of the line width - luminosity relation for spiral galaxies, the Tully-Fisher relation, strongly constrains galaxy formation and evolution models. At this moment, the kinematics of z>1 spiral galaxies can only be measured using rest frame optical emission lines associated with star formation, such as Halpha and [OIII]5007/4959 and [OII]3727. This method has intrinsic difficulties and uncertainties. Moreover, observations of these lines are challenging for present day telescopes and techniques. Here, we present an overview of the intrinsic and observational challenges and some ways way to circumvent them. We illustrate our results with the HST/NICMOS grism sample data of z ~ 1.5 starburst galaxies. The number of galaxies we can use in the final Tully-Fisher analysis is only three. We find a ~2 mag offset from the local rest frame B and R band Tully-Fisher relation for this sample. This offset is partially explained by sample selection effects and sample specifics. Uncertainties in inclination and extinction and the effects of star formation on the luminosity can be accounted for. The largest remaining uncertainty is the line width / rotation curve velocity measurement. We show that high resolution, excellent seeing integral field spectroscopy will improve the situation. However, we note that no flat rotation curves have been observed for galaxies with z>1. This could be due to the described instrumental and observational limitations, but it might also mean that galaxies at z>1 have not reached the organised motions of the present day.Comment: 13 pages, 7 figures, A&A accepte

Gas and Dust Emission from the Nuclear Region of the Circinus Galaxy

Simultaneous modeling of the line and continuum emission from the nuclear region of the Circinus galaxy is presented. Composite models which include the combined effect of shocks and photoionization from the active center and from the circumnuclear star forming region are considered. The effects of dust reradiation, bremsstrahlung from the gas and synchrotron radiation are treated consistently. The proposed model accounts for two important observational features. First, the high obscuration of Circinus central source is produced by high velocity and dense clouds with characteristic high dust-to-gas ratios. Their large velocities, up to 1500 km\s, place them very close to the active center. Second, the derived size of the line emitting region is well in agreement with the observed limits for the coronal and narrow line region of Circinus.Comment: 36 pages, LaTex (including 4 Tables and 9 figures), $$ removed from Abstract To appear in "The Astrophysical Journal