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

IR Colors and Sizes of Faint Galaxies

We present J and Ks band galaxy counts down to J=24 and Ks=22.5 obtained with the new infrared imager/spectrometer, SOFI, at the ESO New Technology Telescope. The co-addition of short, dithered, images led to a total exposure time of 256 and 624 minutes respectively, over an area of $\sim20$ arcmin$^2$ centered on the NTT Deep Field. The total number of sources with S/N$>5$ is 1569 in the J sample and 1025 in the Ks-selected sample. These are the largest samples currently available at these depths. A d$logN$/d$m$ relation with slope of $\sim0.36$ in J and $\sim0.38$ in Ks is found with no evident sign of a decline at the magnitude limit. The observed surface density of ``small'' sources is much lower than ``large'' ones at bright magnitudes and rises more steeply than the large sources to fainter magnitudes. Fainter than $J\sim22.5$ and Ks$\sim21.5$, small sources dominate the number counts. Galaxies get redder in J-K down to J$\sim20$ and Ks$\sim19$. At fainter magnitudes, the median color becomes bluer with an accompanying increase in the compactness of the galaxies. We show that the blue, small sources which dominate the faint IR counts are not compatible with a high redshift ($z>1$) population. On the contrary, the observed color and compactness trends, together with the absence of a turnover at faint magnitudes and the dominance of small sources, can be naturally explained by an increasing contribution of sub-$L^*$ galaxies when going to fainter apparent magnitudes. Such evidence strongly supports the existence of a steeply rising ($\alpha\ll-1$) faint end of the local infrared luminosity function of galaxies - at least for luminosities $L<0.01L^*$.Comment: Accepted for publication on A&A; 15 pages, 13 figure

NICMOS Imaging of Molecular Hydrogen Emission in Seyfert Galaxies

We present NICMOS imaging of broad band and molecular hydrogen emission in Seyfert galaxies. In 6 of 10 Seyferts we detect resolved or extended emission in the 1-0 S(1) 2.121 or 1-0 S(3) 1.9570 micron molecular hydrogen lines. We did not detect emission in the most distant galaxy or in the 2 Seyfert 1 galaxies in our sample because of the luminosity of the nuclear point sources. In NGC 5643, NGC 2110 and MKN 1066, molecular hydrogen emission is detected in the extended narrow line region on scales of a few hundred pc from the nucleus. Emission is coincident with [OIII] and H alpha+[NII] line emission. This emission is also near dust lanes observed in the visible to near-infrared color maps suggesting that a multiphase medium exists near the ionization cones and that the morphology of the line emission is dependent on the density of the ambient media. The high 1-0 S(1) or S(3) H2 to H alpha flux ratio suggests that shock excitation of molecular hydrogen (rather than UV fluorescence) is the dominant excitation process in these extended features. In NGC 2992 and NGC 3227 the molecular hydrogen emission is from 800 and 100 pc diameter `disks' (respectively) which are not directly associated with [OIII] emission and are near high levels of extinction (AV > 10). In NGC 4945 the molecular hydrogen emission appears to be from the edge of a 100 pc superbubble. In these 3 galaxies the molecular gas could be excited by processes associated with local star formation. We confirm previous spectroscopic studies finding that no single mechanism is likely to be responsible for the molecular hydrogen excitation in Seyfert galaxies.Comment: submitted to Ap

A narrow-band search for Ly alpha emitting galaxies at z = 8.8

Aims: The first star forming galaxies in the early universe should be copious Ly alpha emitters, and may play a significant role in ionizing the intergalactic medium (IGM). It has been proposed that the luminosity function of Lya emitting galaxies beyond z~6 may be used to constrain the neutral fraction of the IGM during this epoch. In this work we report on a search for Ly alpha emitters at redshift 8.8. Methods: We performed a narrow band imaging programme using ISAAC at the ESO VLT. Seven fields, covering a total area of 31sq. arcmin and for which optical and broad band infra-red images have been obtained in the GOODS survey, were imaged to a limiting flux (respectively luminosity) of ~ 1.3 x 10^{-17} ergs.s^{-1}.cm^{-2} (respectively ~ 1.3 x 10^{43} ergs.s^{-1} in a narrow band filter centered in a region of low OH sky emission at 1.19 micron. Candidate Lyman alpha emitters are objects that are detected in the ISAAC NB images and undetected in the visible broad band images. Results: No z=8.8 Ly alpha emitting galaxies were detected to a limit approaching recent estimates of the luminosity function at z ~ 6. Our results do suggest, however, that detections or substantial constraints could be achieved by this method in the near future with larger field instruments planned for various telescopes.Comment: 7 pages, accepted for publication in A&

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

The redshift of the gravitationally lensed radio source PKS1830-211

We report on the spectroscopic identification and the long awaited redshift measurement of the heavily obscured, gravitationally lensed radio source PKS 1830-211, which was first observed as a radio Einstein ring. The NE component of the doubly imaged core is identified, in our infrared spectrum covering the wavelength range 1.5-2.5 microns, as an impressively reddened quasar at z=2.507. Our redshift measurement, together with the recently measured time delay (Lovell et al.), means that we are a step closer to determining the Hubble constant from this lens. Converting the time delay into the Hubble constant by using existing models leads to high values for the Hubble constant. Since the lensing galaxy lies very close to the center of the lensed ring, improving the error bars on the Hubble constant will require not only a more precise time delay measurement, but also very precise astrometry of the whole system.Comment: 11 pages, 2 figures, Accepted ApJ

Deep Observations of Lyman Break Galaxies

We summarise the main results of recent work on the Lyman break galaxy population which takes advantage of newly commissioned instrumentation on the VLT and Keck telescopes to push the detection of these objects to new wavelengths and more sensitive limits. We focus in particular on near-infrared observations targeted at detecting emission lines of [O II], [O III], and H-beta and on the first tentative detection of Lyman continuum emission from star forming galaxies at z = 3.Comment: 9 pages, LaTeX, 6 Postscript Figures. To appear in the Proceedings of the ESO Symposium: Deep Fields, ed. S. Cristiani (Berlin: Springer

Kinematics of Galaxies in the Hubble Deep Field South: Discovery of a Very Massive Spiral at z=0.6

We report the first results from a study of the internal kinematics, based on spatially resolved H_alpha velocity profiles, of three galaxies at redshift z~0.6 and one at redshift z~0.8, detected by ISOCAM in the Hubble Deep Field South. The kinematics are derived from high resolution near-infrared VLT spectroscopy. One of the galaxies is a massive spiral which possesses a very large rotational velocity of 460 km/s and contains a mass of 10^12 M_solar (within 20 kpc), significantly higher than the dynamical masses measured in most other local and high redshift spirals. Two of the galaxies comprise a counter-rotating interacting system, while the fourth is also a large spiral. The observed galaxies are representative examples of the morphologies encountered among ISOCAM galaxies. The mass-to-light (M /L_bol) ratios of ISOCAM galaxies lie between those of local luminous IR galaxies and massive spirals. We measure an offset of 1.6+/-0.3 mag in the rest frame B-band and of 0.7+/-0.3 mag in the rest frame I-band when we compare the four ISOCAM galaxies to the local Tully-Fisher B and I-band relations. We conclude that the large IR luminosity of the ISOCAM population results from a combination of large mass and efficient triggering of star formation. Since ISOCAM galaxies contribute significantly to the Cosmic Infrared Background our results imply that a relatively small number of very massive and IR luminous objects contribute significantly to the IR background and star formation activity near z~0.7.Comment: accepted for publication in the Astrophysical Journal (Part 1