Found 6 talks width keyword infrared galaxies

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Thursday May 7, 2015
Dr. Jiasheng Huang
National Astronomical Observatories of China, Beijing and Harvard-Smithsonian Centre for Astrophysics, Cambridge, MA

Abstract

 I will present a multiwavelength study of a large MIPS selected galaxies and satisfy a certain IRAC color criterion. Stellar population modeling and IRS spectra together demonstrate that the double criteria used to select this sample have efficiently isolated massive star-forming galaxies at /z/ ~ 1.9. This is the first starburst (SB)-dominated ultraluminous infrared galaxies (ULIRG) sample at high redshift with total infrared luminosity measured directly from Spitzer, Herschel FIR and millimeter photometry, and as such gives us the first accurate view of broadband spectral energy distributions for SB galaxies at extremely high luminosity and at all wavelengths. The HST images in optical and NIR bands show that most objects have very extended morphologies in the rest-frame ultraviolet and optical band, thus extended distribution of PAH molecules. We conclude that objects in this sample are ULIRGs powered mainly by SB; and the total infrared luminosity density contributed by this type of objects at /z/ ~ 1.9.


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Thursday December 19, 2013
Dr. Daniel Rosa
Instituto Nacional de Astrofisica, Optica y Electronica, Mexico

Abstract

I will present the first Large Millimiter Telescope spectra of 4 nearby galaxies with known high star formation rates. The individual spectra were acquired with the Redshift Search Receiver, a 3 mm spectrograph that covers simultaneously the 3 mm band from 75 to 110 GHz. The spectra show rms temperatures of around 4 mK that allow us to detect not only common molecular species such as CO, HCN, HCO+, HCN, 13CO reported widely in the literature but also other more rare molecular transitions (HC3N, CN, CH3OH, CH3C2H) and even Hydrogen recombination lines (from H39alpha to H42alpha). We are making use of theoretical radiative transfer models to analize these spectra in order to understand the variations of the observed line ratios of different lines in galaxies classified as ultraluminous infrared galaxies where the star formation rate may be as high as 100 solar masses per year. These data will help to understand the physical conditions of the gas in regions that are forming stars very efficiently. The observed line ratios in star forming galaxies are also compared to those galaxies that is known to contain an AGN.


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Thursday October 17, 2013
Dr. B-G Anderson
SOFIA Science Center-USRA

Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is now performing scientific observations and the results of the second open observing cycle solicitation is about to be announced.  With an available wavelength coverage from the visual to sub-mm wavelengths and a long life time - including planned instrument upgrades, SOFIA will provide critical resource for the astronomical community for the next decade and beyond.  Current and expected SOFIA instruments provide heterodyne spectroscopy in the THz band, including the line of [O I], [C II] and [N II] as well as OH, HD and many other hydrides, at high spectral resolution.  Echelle spectroscopy in the Mid-infrared (MIR) which will allow observations of e.g. fine-structure lines of and H2 pure rotational lines.  These will help address questions of interstellar chemistry and physics in star forming regions, PDRs and galaxies.  Mid-infrared (MIR) grism spectroscopy, of e.g. dust and ices, can be used to address questions of the freeze-out of molecules from the gas phase to better understand the formation, destruction and characteristics of interstellar ices.  Imaging in the MIR and FIR and FIR polarimetry can provide a more complete picture of the temperature, density and magnetic field structure of e.g. star forming cores. I will highlight the current and expected capabilities of SOFIA and some of the early science results achieved.


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Thursday May 10, 2012
Dr. Rachel Mason
Gemini Observatory

Abstract

Low-luminosity AGN (LLAGN; LINERs and low-luminosity Seyferts) are present in numerous nearby galaxies and are often suggested to be the "missing link" between bright AGN and "normal", quiescent systems. Their accretion physics appear to differ from those of higher-luminosity AGN, and their place in the AGN unified scheme is not yet clear. Mid-IR observations promise new constraints on the accretion mechanisms and obscuring medium in LLAGN. However, their mid-IR emission remains almost completely unexplored at the high angular resolution needed to separate the weak nucleus from the host galaxy. I will show the results of an exploratory imaging study of ~20 LLAGN using Michelle and T-ReCS on the Gemini telescopes. Combined with Spitzer spectroscopy and high-resolution multi-wavelength information, the data establish, for the first time, the general nuclear IR properties of these objects. There are some hints that the obscuring torus disappears at low AGN luminosities, and we are also able to provide "dust-free" candidates for detailed study of the disk and jets.


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Tuesday February 28, 2012
Dr. Almudena Alonso Herrero
Instituto de Astrofísica de Cantabria, Spain

Abstract

Luminous Infrared Galaxies (LIR=10^11-10^12Lsun) have star formation rates in the range of ~20-200Msun/yr. In the local Universe ~50% LIRGs show AGN or AGN/SB composite nuclear activity from optical spectroscopy. We decompose Spitzer/IRS 5-35micron spectra of a complete sample of 50 local (d<75Mpc) LIRGs using SB and AGN clumpy torus model templates. We derive a mid-IR AGN detection rate in our sample of local LIRGs of 50%. We also compare the continuum mid-IR AGN detection with other indicators in the mid-IR, optical and X-rays. We estimate for the first time the AGN bolometric contribution to the IR luminosity of the galaxies in local LIRGs. We find that one-third of local LIRGs have LAGN(bol)/LIR>0.05, with only ~10% having a significant contribution LAGN(bol)/LIR>0.25. This is in line with results of Nardini et al. (2010) that only at LIR>3x10^12Lsun the AGN starts dominating bolometrically the IR luminosity in the majority of the systems.


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Tuesday April 26, 2011
Dr. Cristina Ramos Almeida
University of Sheffield, UK

Abstract

I will present new mid-infrared imaging data for a sample of ~20 nearby Seyfert galaxies obtained with T-ReCS and MICHELLE on the Gemini Telescopes at subarcsecond resolution. Our aim is to compare the properties of Type-1 and Type-2 Seyfert tori using clumpy torus models and a Bayesian approach to fit the infrared nuclear spectral energy distributions (SEDs). These dusty tori have physical sizes smaller than 10 pc radius, as derived from our fits. Unification schemes of AGN account for a variety of observational differences in terms of viewing geometry. However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Type-1 and Type-2 Seyfert nuclei are intrinsically different. The Type-2 tori studied here are broader, have more clumps, and these clumps have lower optical depths than those of Type-1 tori. The larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In our sample, Seyfert 2 tori have larger covering factors and smaller escape probabilities than those of Seyfert 1. Thus, on the basis of the results presented here, the classification of a Seyfert galaxy as a Type-1 or Type-2 depends more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.


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