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We explore the properties of early-type galaxies (ETGs) in rich environments such as clusters of galaxies. The L24/LK distribution of ETGs in both Virgo and Coma clusters shows that some lenticulars (S0, 10 in Coma and 3 in Virgo) have a much larger L24/LK ratio (0.5 to ~2 dex) than the bulk of the ETG population. We call these sources Mid-Infrared Enhanced Galaxies (MIEGs). In Coma, they are mostly located in the South-West part of the cluster where a substructure is falling onto the main cluster. MIEGs present lower g-r color than the rest of the ETGs, because of a blue continuum. We interpret the excess L24/LK ratio as evidence for an enhanced star-formation induced as a consequence of their infall into the main cluster.
We present a multi-wavelength study of a nearby radio loud elliptical galaxy NGC 708, selected from the Bologna B2 sample of radio galaxies. We obtained optical broad band and narrow images from IGO 2m telescope (Pune, India). We supplement the multi-wavelength coverage of the observation by using X-ray data from Chandra, infrared data from 2MASS, Spitzer and WISE and optical image from DSS and HST. In order to investigate properties of interstellar medium, we have generated unsharp-masked, color, residual, quotient, dust extinction, Hα emission maps. From the derived maps it is evident that cool gas, dust, warm ionized Hα and hot X-ray gas are spatially associated with each other. We investigate the inner and outer photometric and kinematic properties of the galaxy using surface brightness profiles. From X-ray 2d beta model, unsharp masking, surface brightness profiles techniques, it is evident that pair of X-ray cavities are present in this system and which are ~5.6 Kpc away from the central X-ray source.
We present high resolution molecular line observations of dusty AGN and starburst in nearby luminous infrared galaxies (LIRGs), VV 114 (band 3/4/7) and NGC 1614 (band 3/6/7/9), with ALMA. Multi-frequency imaging from 4.8 GHz to 691 GHz of NGC 1614 allows us to study spatial properties of the radio-to-FIR continuum and multiple CO transitions, and we find the CO excitation up to Jupp = 6 can be explained by a single ISM model powered by nuclear starbursts. Our processing line imaging survey for VV 114 detected at least 30 molecular lines which show different chemical composition from region to region. Multi-molecule imaging helps us to diagnose the chemical differences of dusty ISM, while multi-transition imaging allows us to investigate gas physical conditions affected by nuclear activities directly.
We performed three-dimensional hydrodynamical simulations of idealized giant molecular cloud collisions including star formation and radiative transfer. We found that the characteristics of the colliding systems are similar to the observations of the Spitzer bubbles, suggesting these objects could be created in such interactions. A high velocity collision creates a top-heavy core mass distribution but is not strongly affected by radiation. At lower collision speeds, the HII regions have time to expand within the shock and promote the formation of massive cores.
The stellar initial mass function (IMF) is a fundamental astrophysical quantity that impacts a wide range of astrophysical problems from heavy element distribution to galactic evolution to planetary system formation. However, the origin and universality of the IMF are hotly debated both observationally and theoretically. I review recent observations of the IMF across a variety of environments. These suggest the IMF is surprisingly invariant between star-forming regions, star clusters, and spiral galaxies but that it may also vary under extreme conditions, including within the Galactic center and early type galaxies.
We present star formation rates and nebular abundances of 59 different star-forming regions in 16 nearby galaxies. The star-forming regions were selected to be bright in Hα and were observed with the SNIFS integral field spectrograph on the UH 2.2m telescope. The spectra span the wavelength range between 3200Å and 1μm. We find that the local star formation rates depend on the local abundances in that low SFRs show a dependence but high SFR appear insensitive to it.
It is crucially important to observe dense cores in order to investigate the initial condition of star formation since protostars are formed via dynamical collapse of dense cores, inhering the physical properties from their natal dense cores. Here we present the results of ALMA Cycle 0 and Cycle 1 observations of dust continuum emission and molecular rotational lines toward a dense core, MC27 (aka L1521F), which is considered to be very close to the first protostellar core phase. We revealed the spatial/velocity structures of the core are very complex and and suggest that the star formation is highly dynamical.
Star formation and interstellar medium (ISM) structure were investigated in the Taurus, Auriga, Perseus and California (TAP) nearby star forming regions. Properties of the cold ISM was derived using AKARI FIR all sky maps, the Osaka-1.85m CO survey focusing to the all-sky Planck catalogue of Galactic Cold Clumps (PGCC). As many as 1041 infrared point sources were classified as young stellar object (YSO) based on multiband photometric data, and 384 of those are associated to a PGCC object. About 30% of the TAP PGCC clumps have associated YSOs.
We summarize results from our recent SDSS survey for CaII quasar absorbers. The survey finds 435 absorbers at z<1.34, which corresponds to ~9 Gyrs of the Universe's history. Two CaII absorber populations are identified, which we call weak and strong. Metal abundance ratios derived from normalized composite spectra show that weak absorbers can be identified with halo-like gas, while strong absorbers are a mix of halo+disk-like gas. Consistent with these abundance ratio results, fluxed composites show that strong absorbers are ~6 times more reddened than weak absorbers (i.e., they contain more dust). Four individual examples of galaxies associated with CaII absorption are found in the SDSS images, and three are star forming galaxies (SFGs). Image composites show that galaxies associated with strong absorbers have mean luminosity-weighted impact parameters, b, which are ~2.4 times smaller than the weak absorbers (bstrong ~ 19 kpc versus bweak 45 kpc). Studies of CaII absorbers suggest links to molecular clouds, SFGs, and circumgalactic gas (CGG).
We present our approach of visibility modeling of disks around low-mass (< 2 M⊙) young stellar objects (YSOs). We compiled an atlas based on mid-infrared interferometric observations from the MIDI instrument at the VLTI. We use three different models to fit the data. These models allow us to determine overall sizes (and the extent of the inner gaps) of the modeled circumstellar disks.
We created the Herschel1 Footprint Database and web services for the Herschel Space Observatory imaging data. For this database we set up a unified data model for the PACS and SPIRE Herschel instruments, from the pointing and header information of each observation, generated and stored sky coverages (footprints) of the observations in their exact geometric form. With this tool we extend the capabilities of the Herschel Science Archive by providing an effective search tool that is able to find observations for selected sky locations (objects), or even in larger areas in the sky.
We have analyzed multi-wavelength mid-infrared images of the central parsec of the Galactic Center using a two-temperature line-of-sight (LOS) radiative transfer model at each pixel of the images, giving maps of temperatures, luminosities and opacities of the hot, warm, cold (dark) dust components. The data consists of images at nine wavelengths in the mid-infrared (N-band and Q-band) from the Thermal Region Camera and Spectrograph (T-ReCS) instrument operating at the Gemini South Observatory. The results of the LOS modeling indicate that the extinction optical depth is quite large and varies substantially over the FOV.
IC5146 is one of the filamentary clouds observed in Herschel Gould Belt Survey. Here we present our polarization observations toward IC5146 taken with AIMPOL, TRIPOL and Mimir. Our results reveal that the large scale structure of magnetic field is well perpendicular to the main filament, but is likely parallel to the sub-filaments, which are structure extended out from the main filaments. We have also conducted CO observations to reveal the gas kinematics along the filaments or magnetic field; this result suggests the gas is possibly confined by magnetic field in most of the region until reaching supercritical. Based on our results, we suggests that at least four types of filaments can be found in IC5146, behaving different physical properties and consistent with different formation mechanisms. Our conclusions reveal that filaments are a combination of a variety types of objects.
Recent surveys at infrared and submillimeter wavelengths with the Spitzer and Herschel space observatories suggest that star formation in dense molecular gas is governed by essentially the same “laws” in nearby Galactic clouds and distant external galaxies. This raises the possibility of a unified picture for star formation in the Universe from individual-cloud scales to galaxy–wide scales. We summarize the star formation scenario favored by Herschel studies of the nearest molecular clouds of the Galaxy which point to the key role of the quasi-universal filamentary structure pervading the cold interstellar medium.
At distances of ~50 kpc and ~60 kpc for the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) respectively the Magellanic Clouds present us with a unique opportunity to study star formation in environments outside our own galaxy. Through Spitzer and Herschel photometry and spectroscopy, samples of Young Stellar Objects (YSOs) have been selected and spectroscpically confirmed in the Magellanic Clouds. Here we present some of the key results of our SINFONI K-band observations towards massive YSOs in the Magellanic Clouds. We resolve a number of Spitzer sources into multiple, previously unresolved, components and our analysis of emission lines suggest higher accretion rates and different disc properties compared with massive YSOs in the Milky Way.
Recent Fabry-Pérot observations towards the galaxy NGC 1325 with the Southern African Large Telescope (SALT) led to the serendipitous discovery of an emission feature centered at 661.3 nm arising from material in the interstellar medium (ISM) of our Galaxy; this emission feature lies at the wavelength of one of the sharper and stronger diffuse bands normally seen in absorption. The flux of the feature is 4.2 ± 0.5 × 10−18 es−1 cm−2 arcsec−2. It appears that this is the first observation of emission from a diffuse band carrier in the ISM, excited in this case by the interstellar radiation field. We present the discovery spectra and describe follow-up measurements proposed for SALT.
In this study, we examine the effect of surface density of disks on chemical evolution of galaxies. We find that, higher surface brightness galaxies on average possess higher gas-phase metallicity compared to lower surface brightness galaxies with the same stellar and gas mass. The surface brightness effect is more significant for low-mass galaxies. Using an analytical model of chemical evolution involving gas outflow and accretion, we find that the surface brightness dependence can be attributed to the strength of inflowing pristine gas. Galaxies with lower surface brightness experience stronger inflow than galaxies with a higher surface brightness of a similar mass.
We have observed 3 pairs of interacting galaxies (the Antennae, Arp 236, and NGC 1614) using the Fabry-Perot interferometer GHαFaS (Galaxy Hα Fabry-Perot system) on the 4.2m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos, La Palma. We have extracted the physical properties (sizes, Hα luminosity and velocity dispersion) of Hii regions. We have combined also these observations with ALMA archival observations of these interacting galaxies, finding that there is a set of brighter and denser star forming regions. We have been able to compare these properties with those of two SMGs at redshift ~ 2.
I review some steps in the conversion of molecular cloud gas into stars and planets, with an emphasis in this presentation on the early stage molecular cloud fragmentation that leads to elongated filaments/ribbons. Magnetic fields can play a crucial role in all stages and need to be invoked particularly for early stage fragmentation as well as in late core collapse where it may control disk formation. I also review some elements of hydrodynamic modeling of disk evolution.
All 119 OH maser galaxies (110 out of them are megamasers, i.e., LOH > 10 L⊙, OHMs) published so far were compiled and were cross-identified with the Wide-Field Infrared Survey Explorer (WISE) catalog. Our aim is to investigate intrinsic middle-infrared properties of OH maser galaxies and try to find some hints on sample selections on OHM surveys through the coming Five hundred aperture spherical telescope (FAST). In addition, enormous potentials for OHM surveys by future FAST are investigated, based on its innovative designs and its expected best sensitivity among single dish telescopes.