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 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

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

VLT/VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies: 2D kinematic properties

We present and discuss the 2D kinematic properties of the ionized gas (Halpha) in a sample of 38 local (ultra) luminous infrared galaxies [(U)LIRGs] (31 LIRGs and 7 ULIRGs) observed with VIMOS at the VLT using integral field spectroscopy. This sample covers well the less studied LIRG luminosity range and includes isolated disks, interacting systems, and mergers. The majority of the galaxies have two main kinematically distinct components. One component (i.e., narrow or systemic) extends over the whole line-emitting region and is characterized by small to intermediate velocity dispersions (i.e., sigma from 30 to 160 km s^-1). It traces the overall velocity field. The second component (broad) has in general a larger velocity dispersion (up to 320 km s^-1), mainly found in the inner regions and generally blueshifted with respect to the systemic component. Most of the objects (76%) are dominated by rotation, more relevant in LIRGs than in ULIRGs. Isolated disks, interacting galaxies, and merging systems define a sequence of increasing mean velocity dispersion, and decreasing velocity field amplitude.The LIRGs classified as isolated disks have similar velocity amplitudes but larger mean velocity dispersions (44 vs. 24 km s^-1) than local spirals, implying a larger turbulence and thicker disks. Interacting systems and mergers have values closer to those of low velocity dispersion ellipticals/lenticular galaxies (E/SOs). The (U)LIRGs classified as mergers have kinematic properties similar to those shown by the Lyman break analogs (LBAs). The dynamical masses range from \sim 0.04 m* to 1.4 m* (i.e., m* = 1.4x10^{11} Msun), with ULIRGs (M{dyn} sim 0.5 +/- 0.2 m*) being more massive than LIRGs by, on average, a factor of about 2. The mass ratio of individual pre-coalescence galaxies is <2.5 for most of the systems, confirming that most (U)LIRG mergers involve sub-m* galaxies of similar mass.Comment: 66 pages, 5 figures plus 45 figures in App. A; accepted for publication in A&

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.

Effect of disulfide bond scrambling on protein stability, aggregation, and cytotoxicity

Proteins are nano-machines that carry out majority of the cellular functions. Thermodynamically they are functional and stable within a very narrow range (1 kcal/mol). External perturbations in the form of pH change, thermal, or oxidative/reducing stress can destabilize the protein resulting in misfolding and aggregation. Prolonged environmental stress can affect the cells adaptive response resulting in loss of ability to refold or recycle proteins. This can lead to accumulation of misfolded or aggregated proteins within the cell. Such accumulation of aggregated proteins have been associated with neurodegenerative disorders such as Amyotrophic Lateral Sclerosis (ALS), Parkinson’s, Huntington’s, and Alzheimer’s disease. There is a general consensus among scientists that aggregated proteins cause disease by a ‘toxic gain of function’. However, there is a huge debate among scientists on what are the toxic forms of protein aggregates. This is largely due to lack of research that have looked at the relationship between morphology of aggregates and their toxicity. Therefore, such studies that can help clarify the relationship between morphologically different forms of aggregates and their associated toxicity are needed. In this dissertation, we study how disulfide reducing environment can impact protein stability, aggregation, and cytotoxicity. We also study effect of molecular crowding agent polyethylene glycol (PEG) (600 and 2000 g/mol) on providing protection against reducing and thermal stress. Disulfide bonds are covalent interactions that provide major stability to the protein in conjunction with several non-covalent interactions such as hydrophobic interactions, hydrogen bonding, Van der Waal and electrostatic interactions. These interactions help the proteins to fold into its native three-dimensional fold. However, the cytoplasmic environment in cells is highly reducing and can compromise the disulfide bonds leading to protein aggregation. To better understand how disulfide bond scrambling can affect protein aggregation, we used insulin as a model protein. We made seeds of insulin by incubating the protein in presence of disulfide reducing agent for varying lengths of time at 37 °C. These seeds were labeled as ‘nascent’, ‘intermediate’, or ‘mature’ based on their ability to induce and promote aggregation of native protein with different kinetics. Nascent seeds promoted fastest insulin aggregation and formed amorphous aggregates. In another related study we used a combination of pH (acidic to basic) and temperature (37 and 65 °C) to generate morphologically different types of insulin aggregates under disulfide reducing/non-reducing conditions. These aggregates were characterized by different techniques and tested for their toxicity on SH-SY5Y cells. Cytotoxicity studies of insulin aggregates on neuroblastoma cells showed that aggregates formed from disulfide reduced proteins at acidic pH were more toxic compared to the aggregates formed at neutral or basic pH. Lastly, we wanted to study how these properties could be impacted by molecular crowding. We mimicked the intracellular crowded milieu in vitro by using PEG to investigate the effect of crowding on lysozyme stability and aggregation under thermal and reducing stress. We observed that PEG-2000 stabilized the molten globule intermediate of lysozyme in the presence of a non-thiol based reducing agent. Overall, the results indicates an intricate relationship of pH, temperature, and reducing environment impacting proteins aggregation and its associated toxicity