Integral field optical spectroscopy of a representative sample of ULIRGs: II. Two-dimensional kpc-scale extinction structure

We investigate the two-dimensional kpc-scale structure of the extinction in a representative sample of local ULIRGs using the Halpha/Hbeta line ratio.We use optical integral field spectroscopy obtained with the INTEGRAL instrument at the William Herschel Telescope. Complementary optical and near-IR high angular resolution HST images have also been used. The extinction exhibits a very complex and patchy structure in ULIRGs on kpc scales, from basically transparent regions to others deeply embedded in dust (Av~0.0 to Av~8.0 mag). Nuclear extinction covers a broad range in Av from 0.6 to 6 mag, 69% of the nuclei having Av>2.0 mag. Extinction in the external regions is substantially lower than in the nuclei with 64% of the ULIRGs in the sample having median Av of less than 2 mag for the entire galaxy. While post-coalescence nuclei tend to cluster around Av values of 2 to 3 mag, pre-coalescence nuclei appear more homogeneously distributed over the entire 0.4 mag <Av< 7.7 mag range. For the average extinction (Av~2.0 derived for the ULIRGs of the sample, the ratio of the de-reddened to observed SFR values is 6. The extinction-corrected, Halpha-based SFR ranges from 10 to 300 Msun/yr. For only 28% of the cases the de-reddened SFR is <20 Msun/yr, whereas for the observed SFR this percentage increases to 72%. The IR-based SFR is always higher than the optical-based one, with differences ranging from about 2 to up to 30. The nuclear observed SFR has an average contribution to the total one of 16% for the entire sample. Once corrected for extinction, the average value becomes 31%. Because of mostly extinction effects, the optical (I-band) half-light radius in the sample galaxies is on average a factor 2.3 larger than the corresponding near-IR (H-band) value.Comment: To appear in A&

Integral Field Spectroscopy of Mrk 273: Mapping 10^3 km/s Gas Flows and an Off-Nucleus Seyfert 2 Nebula

Integral field optical spectroscopy with the INTEGRAL fiber-based systemis used to map the extended ionized regions and gas flows in Mrk 273, one of the closest Ultraluminous Infrared galaxies (ULIRGs). The Hbeta and [OIII]5007 maps show the presence of two distinct regions separated by 4'' (3.1 kpc) along position angle (PA) 240. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [OIII] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [OIII] ionized gas shows (i) the presence of highly disturbed gas in the regions around the LINER nucleus, (ii) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 x 10^3 km/s, and (iii) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst, and that the quiescent gas is directly ionized by a nuclear source, like the ionization cones typically seen in Seyfert galaxies.Comment: ApJ Letters, in pres

Radio jets in colliding galaxies: Testing the interaction-activity connection

The idea that galaxy interactions and merging are related to the generation of starburst and AGN activity in galactic nuclei has been the subject of intensive investigations over the past several years and is still a matter of lively debate. Peculiar morphologies, indicative of tidal interactions, have been detected in high-luminosity radio galaxies, in quasars, and in ultraluminous IRAS galaxies. In addition, low-luminosity radio and active galaxies show similar evidence for a recent merger or for nearby companions. In a recent CCD optical study of galaxies selected on the basis that they all contain well defined radio jets, it was found that almost half of the sample consists of pairs of elliptical galaxies. Many of these low-luminosity radio galaxies with companions show a well defined distorted radio jet structure at the VLA scale with an S- or C-shaped morphology. We have developed a general numerical simulation algorithm for ballistic radio jets with the intention of applying this model to the study of the bent jets seen in colliding pairs of galaxies and with the hope of testing the well documented interaction-activity connection. In our model the morphological evolution of the jets is determined by their response to the simple mechanical forces (i.e., gravity and ram pressure) imposed on them from both the host and the companion galaxies. Radiative losses, jet precession, magnetic effects, relativistic terms, and hydrodynamic instabilities have all been ignored. Starting with a previously derived collision model for the interacting pair of elliptical galaxies NGC 4782/4783, we have used our algorithm to simulate the specific two-sided jet morphology seen in the radio source 3C 278, associated with NGC 4782. This is the first time that such jet simulations have been produced for a galaxy pair whose relative orbit was determined independently from the jet modeling

Radio monitoring of NGC 7469: Late time radio evolution of SN 2000ft and the circumnuclear starburst in NGC 7469

We present the results of an eight-year long monitoring of the radio emission from the Luminous Infrared Galaxy (LIRG) NGC 7469, using 8.4 GHz Very Large Array (VLA) observations at 0.3'' resolution. Our monitoring shows that the late time evolution of the radio supernova SN 2000ft follows a decline very similar to that displayed at earlier times of its optically thin phase. The late time radio emission of SN 2000ft is therefore still being powered by its interaction with the presupernova stellar wind, and not with the interstellar medium (ISM). Indeed, the ram pressure of the presupernova wind is \rho_w v_w^2 \approx 7.6E-9 dyn/cm^2, at a supernova age of approximately 2127 days, which is significantly larger than the expected pressure of the ISM around SN 2000ft. At this age, the SN shock has reached a distance r_{sh \approx 0.06 pc, and our observations are probing the interaction of the SN with dense material that was ejected by the presupernova star about 5820 years prior to its explosion. From our VLA monitoring, we estimate that the swept-up mass by the supernova shock after about six years of expansion is \approx 0.29 M_sun, assuming an average expansion speed of the supernova of 10000 km/s. We also searched for recently exploded core-collapse supernovae in our VLA images. Apart from SN 2000ft (S_\nu \approx 1760 microJy at its peak, corresponding to 1.1E28 erg/s/Hz, we found no evidence for any other radio supernova (RSN) more luminous than \approx 6.0E26 erg/s/Hz, which suggests that no other Type IIn SN has exploded since 2000 in the circumnuclear starburst of NGC 7469.Comment: 10 pages, 5 figures, accepted for publication in MNRA

Severe osteoarticular involvement in isotretinoin-triggered acne fulminans: two cases successfully treated with anakinra.

Acne fulminans (AF) is a severe form of inflammatory and ulcerated acne associated with fever, malaise, joint swellings and polyarthralgia.1 Osteoarticular lesions are often described and can be radiologically indistinguishable from those observed in synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome.2,3 SAPHO is an autoinflammatory disease characterized by osteoarticular and cutaneous manifestations, the latter including nodular and fulminans acne, hidradenitis suppurativa and palmoplantar pustulosis.3 Thus, AF is considered part of the SAPHO spectrum.

IC5063: A merger with a hidden luminous active nucleus

IC5063 is a nearby galaxy classified as an SO and containing a system of dust lanes parallel to its major optical axis (Danziger, Goss and Wellington, 1981; Bergeron, Durret and Boksenberg, 1983). Extended emission line regions with high excitation properties have been detected over distances of up to 19 kpc from the nucleus. This galaxy has been classified as Seyfert 2 on the basis of its emission line spectrum. These characteristics make IC5063 one of the best candidates for a merger remnant and an excellent candidate for a hidden luminous active nucleus. Based on new broad and narrow band images and long-slit spectroscopy obtained at the ESO 3.6 m telescope, the authors present some preliminary results supporting this hypothesis

Spatially resolved kinematics of the central regions of M83: hidden mass signatures and the role of supernovae

The barred grand-design spiral M83 (NGC 5236) is one of the most studied galaxies given its proximity, orientation, and particular complexity. Nonetheless, many aspects of the central regions remain controversial conveying our limited understanding of the inner gas and stellar kinematics, and ultimately of the nucleus evolution. In this work, we present AO VLT-SINFONI data of its central ~235x140 pc with an unprecedented spatial resolution of ~0.2 arcsec, corresponding to ~4 pc. We have focused our study on the distribution and kinematics of the stars and the ionised and molecular gas by studying in detail the Pa_alpha and Br_gamma emission, the H_2 1-0S(1) line at 2.122 micron and the [FeII] line at 1.644 micron, together with the CO absorption bands at 2.293 micron and 2.323 micron. Our results reveal a complex situation where the gas and stellar kinematics are totally unrelated. Supernova explosions play an important role in shaping the gas kinematics, dominated by shocks and inflows at scales of tens of parsecs that make them unsuitable to derive general dynamical properties. We propose that the location of the nucleus of M83 is unlikely to be related to the off-centre 'optical nucleus'. The study of the stellar kinematics reveals that the optical nucleus is a gravitationally bound massive star cluster with M_dyn = (1.1 \pm 0.4)x10^7 M_sun, formed by a past starburst. The kinematic and photometric analysis of the cluster yield that the stellar content of the cluster is well described by an intermediate age population of log T(yr) = 8.0\pm0.4, with a mass of M \simeq (7.8\pm2.4)x10^6 M_sun.Comment: 14 pages, 10 figures, accepted for publication in Ap