Physical Sciences and Mathematics Commons^™

Pumping Up The [N I] Nebular Lines, Gary J. Ferland, W. J. Henney, C. R. O'Dell, R. L. Porter, P. A. M. Vanhoof, R. J. R. Williams

Physics and Astronomy Faculty Publications

The optical [N I] doublet near 5200 Å is anomalously strong in a variety of emission-line objects. We compute a detailed photoionization model and use it to show that pumping by far-ultraviolet (FUV) stellar radiation previously posited as a general explanation applies to the Orion Nebula (M42) and its companion M43; but, it is unlikely to explain planetary nebulae and supernova remnants. Our models establish that the observed nearly constant equivalent width of [N I] with respect to the dust-scattered stellar continuum depends primarily on three factors: the FUV to visual-band flux ratio of the stellar population, the optical properties …

Herschel Observations Of Extended Atomic Gas In The Core Of The Perseus Cluster, R. Mittal, J. B. R. Oonk, Gary J. Ferland, A. C. Edge, C. P. O'Dea, S. A. Baum, J. T. Whelan, R. M. Johnstone, F. Combes, P. Salomé, A. C. Fabian, G. R. Tremblay, M. Donahue, Russell H. H.

Physics and Astronomy Faculty Publications

We present Herschel observations of the core of the Perseus cluster of galaxies. Especially intriguing is the network of filaments that surround the brightest cluster galaxy, NGC 1275, previously imaged extensively in Hα and CO. In this work, we report detections of far-infrared (FIR) lines, in particular, [C II] 158, [O I] 63, [N II] 122, [O IB] 145 and [O III] 88  μm, withHerschel. All lines are spatially extended, except [O III], with the [C II] line emission extending up to 25 kpc from the core. [C II] emission is found to be co-spatial with Hα and …

Dust And The Type Ii-Plateau Supernova 2004dj, W. P. S. Meikle, R. Kotak, D. Farrah, S. Mattila, S. D. Van Dyk, A. C. Andersen, R. Fesen

Dartmouth Scholarship

We present mid-infrared (MIR) spectroscopy of a Type II-plateau supernova, SN 2004dj, obtained with the Spitzer Space Telescope, spanning 106-1393 days after explosion. MIR photometry plus optical/near-IR observations are also reported. An early-time MIR excess is attributed to emission from non-silicate dust formed within a cool dense shell (CDS). Most of the CDS dust condensed between 50 days and 165 days, reaching a mass of 0.3 × 10^–5 M _☉. Throughout the observations, much of the longer wavelength (>10 μm) part of the continuum is explained as an IR echo from interstellar dust. The MIR excess …

Kingfish -- Key Insights On Nearby Galaxies: A Far-Infrared Survey With Herschel: Survey Description And Image Atlas, R. C. Kennicutt, Daniela Calzetti, G. Aniano, P. Appleton, L. Armus, P. Beirão, A. D. Bolatto, B. Brandl, A. Crocker, K. Croxall, D. A. Dale, J. Donovan Meyer, B. T. Draine, C. W. Engelbracht, M. Galametz, K. D. Gordon, B. Groves, C.-N. Hao, G. Helou, J. Hinz, L. K. Hunt, B. Johnson, J. Koda, O. Krause, A. K. Leroy, Y. Li, S. Meidt, E. Montiel, E. J. Murphy, N. Rahman, H.-W. Rix, H. Roussel, K. Sandstrom, M. Sauvage, E. Schinnerer, K. Skibba, J. D. T. Smith, S. Srinivasan, L. Virgroux, F. Walter, C. D. Wilson, M. Wolfire, S. Zibetti

Daniela Calzetti

The KINGFISH project (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) is an imaging and spectroscopic survey of 61 nearby (d < 30 Mpc) galaxies, chosen to cover a wide range of galaxy properties and local interstellar medium (ISM) environments found in the nearby Universe. Its broad goals are to characterize the ISM of present-day galaxies, the heating and cooling of their gaseous and dust components, and to better understand the physical processes linking star formation and the ISM. KINGFISH is a direct descendant of the Spitzer Infrared Nearby Galaxies Survey (SINGS), which produced complete Spitzer imaging and spectroscopic mapping and a comprehensive set of multi-wavelength ancillary observations for the sample. The Herschel imaging consists of complete maps for the galaxies at 70, 100, 160, 250, 350, and 500 microns. The spectal line imaging of the principal atomic ISM cooling lines ([OI]63um, [OIII]88um, [NII]122,205um, and [CII]158um) covers the subregions in the centers and disks that already have been mapped in the mid-infrared with Spitzer. The KINGFISH and SINGS multi-wavelength datasets combined provide panchromatic mapping of the galaxies sufficient to resolve individual star-forming regions, and tracing the important heating and cooling channels of the ISM, across a wide range of local extragalactic ISM environments. This paper summarizes the scientific strategy for KINGFISH, the properties of the galaxy sample, the observing strategy, and data processing and products. It also presents a combined Spitzer and Herschel image atlas for the KINGFISH galaxies, covering the wavelength range 3.6 -- 500 microns. All imaging and spectroscopy data products will be released to the Herschel user generated product archives.

Dust-Corrected Star Formation Rates Of Galaxies. Ii. Combinations Of Ultraviolet And Infrared Tracers, Cai-Na Hao, C. Kennicutt Kr., Benjamin D. Johnson, Daniela Calzetti, Daniel A. Dale, John Moustakas

Daniela Calzetti

We present new calibrations of far-ultraviolet (FUV) attenuation as derived from the total infrared to FUV luminosity ratio (IRX) and the FUV-NUV color. We find that the IRX-corrected FUV luminosities are tightly and linearly correlated with the attenuation-corrected H\alpha\ luminosities (as measured from the Balmer decrement), with a rms scatter of $\pm 0.09$ dex. The ratios of these attenuation-corrected FUV to H\alpha\ luminosities are consistent with evolutionary synthesis model predictions, assuming a constant star formation rate over 100 Myr, solar metallicity and either a Salpeter or a Kroupa IMF with lower and upper mass limits of 0.1 and 100\msun. The …

The Emission By Dust And Stars Of Nearby Galaxies In The Herschel Kingfish Survey, Ramin A. Skibba, Charles W. Engelbracht, Daniel Dale, Joannah Hinz, Stefano Zibetti, Alison Crocker, Brent Groves, Leslie Hunt, Benjamin D. Johnson, Sharon Meidt, Eric J. Murphy, Philip Appleton, Lee Armus, Alberto Bolatto, Bernhard Brandl, Daniela Calzetti, Kevin Croxall, Maud Galametz, Karl. D. Gordon, Robert C. Kennicutt, Jin Koda, Oliver Krause, Edward Montiel, Hans-Walter Rix, Hélène Roussel, Karin Sandstrom, Marc Sauvage, Eva Schinnerer, J. D. Smith, Fabian Walter, Christine D. Wilson, Mark Wolfire

Daniela Calzetti

Using new far-infrared imaging from the Herschel Space Observatory with ancillary data from ultraviolet to submillimeter wavelengths, we estimate the total emission from dust and stars of 62 nearby galaxies in the KINGFISH survey in a way that is as empirical and model-independent as possible. We collect and exploit these data in order to measure from the spectral energy distributions (SEDs) precisely how much stellar radiation is intercepted and re-radiated by dust, and how this quantity varies with galaxy properties. By including SPIRE data, we are more sensitive to emission from cold dust grains than previous analyses at shorter wavelengths, …

Monster In The Dark: The Ultraluminous Grb 080607 And Its Dusty Environment, D.A. Perley, A.N. Morgan, Adria Updike, F. Yuan, C.W. Akerlof, A.A. Miller, J.S. Bloom, S.B. Cenko, W. Li, A.V. Filippenko, J.X. Prochaska, D.A. Kann, N.R. Tanvir, A.J. Levan, N.R. Butler, P. Christian, D.H. Hartmann, P. Milne, E.S. Rykoff, W. Rujopakarn, J.C. Wheeler, G.G. Williams

Arts & Sciences Faculty Publications

We present early-time optical through infrared photometry of the bright Swift gamma-ray burst (GRB) 080607, starting only 6 s following the initial trigger in the rest frame. Complemented by our previously published spectroscopy, this high-quality photometric data set allows us to solve for the extinction properties of the redshift 3.036 sightline, giving perhaps the most detailed information to date on the ultraviolet continuum absorption properties of any sightline outside our Local Group. The extinction properties are not adequately modeled by any ordinary extinction template (including the average Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud curves), partially because the …

The Seds And Host Galaxies Of The Dustiest Grb Afterglows, T. Krühler, J. Greiner, P. Schady, S. Savaglio, P. M.J. Afonso, C. Clemens, J. Elliott, R. Filgas, D. Gruber, D. A. Kann, S. Klose, A. Küpcü-Yoldas, S. Mcbreen, F. Olivares, D. Pierini, A. Rau, A. Rossi, M. Nardini, A. Nicuesa Guelbenzu, V. Sudilovsky, Adria Updike

Arts & Sciences Faculty Publications

No abstract provided.

Gamma Ray Bursts As Probes Of Dust In The Evolving Universe, Adria Updike

All Dissertations

Dust is ubiquitous in the universe. Understanding where it comes from and where we observe it can have major implications to all astronomical observations. In this study, we investigate how gamma ray bursts (GRBs) can be used as probes of dust in the evolving universe. Making the simplification that silicate dust comes from core collapse supernovae and that graphite dust is produced in the winds of low- to intermediate-mass stars, we present numerical simulations of the resulting dust evolution in GRB hosts and show how the SEDs evolve. Dust extinction laws are re-derived from scattering theory of small particles and …

Monster In The Dark: The Ultraluminous Grb 080607 And Its Dusty Environment, Dieter H. Hartmann, D. A. Perley, A. N. Morgan, A. Updike, F. Yuan, C. W. Awkerlof, A. A. Miller, J. S. Bloom, S. B. Cenko, W. Li

Publications

We present early-time optical through infrared photometry of the bright gamma-ray burst GRB 080607, starting only 6 s following the initial trigger in the rest frame. Complemented by our previously published spectroscopy, this high-quality photometric dataset allows us to solve for the extinction properties of the redshift 3.036 sightline, giving perhaps the most detailed information on the ultraviolet continuum absorption properties of any sightline outside our Local Group to date. The extinction properties are not adequately modeled by any ordinary extinction template (including the average Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud curves), partially because the 2175 A …

Herschel Images Of Ngc 6720: H2 Formation On Dust Grain, P. A. M. Van Hoof, G. C. Van De Steene, M. J. Barlow, K. M. Exter, B. Sibthorpe, T. Ueta, V. Peris, M. A. T. Groenewegen, J. A. D. L. Blommaert, M. Cohen, W. De Meester, Gary J. Ferland, W. K. Gear, H. L. Gomez, P. C. Hargrave, E. Huygen, R. J. Ivison, C. Jean, S. J. Leeks, T. L. Lim, G. Olofsson, E. T. Polehampton, S. Regibo, P. Royer, B. M. Swinyard, B. Vandenbussche, H. Van Winckel, C. Waelkens, H. J. Walker, R. Wesson

Physics and Astronomy Faculty Publications

Herschel PACS and SPIRE images have been obtained of NGC 6720 (the Ring nebula). This is an evolved planetary nebula with a central star that is currently on the cooling track, due to which the outer parts of the nebula are recombining. From the PACS and SPIRE images we conclude that there is a striking resemblance between the dust distribution and the H₂ emission, which appears to be observational evidence that H₂ forms on grain surfaces. We have developed a photoionization model of the nebula with the Cloudy code which we used to determine the physical conditions of …

An Investigation Of The Dust Content In The Galaxy Pair Ngc 1512/1510 From Near-Infrared To Millimeter Wavelengths, Gl Liu, D Calzetti, Min Yun, Gw Wilson, Bt Draine, K Scott, J Austermann, T Perera, D Hughes, I Aretxaga, K Kohno, R Kawabe, H Ezawa

Astronomy Department Faculty Publication Series

We combine new ASTE/AzTEC 1.1 mm maps of the galaxy pair NGC 1512/1510 with archival Spitzer IRAC and MIPS images covering the wavelength range 3.6-160 μm from the SINGS project. The availability of the 1.1 mm map enables us to measure the long-wavelength tail of the dust emission in each galaxy, and in sub-galactic regions in NGC 1512, and to derive accurate dust masses. The two galaxies form a pair consisting of a large, high-metallicity spiral (NGC 1512) and a low-metallicity, blue compact dwarf (NGC 1510), which we use to compare similarities and contrast differences. Using the models of Draine …

Pacs And Spire Photometer Maps Of M 33: First Results Of The Herschel M 33 Extended Survey (Herm33es), C Kramer, C Buchbender, E Xilouris, M Boquien, J Braine, D Calzetti

Astronomy Department Faculty Publication Series

Context. Within the framework of the HERM33ES key program, we are studying the star forming interstellar medium in the nearby, metal-poor spiral galaxy M 33, exploiting the high resolution and sensitivity of Herschel. Aims. We use PACS and SPIRE maps at 100, 160, 250, 350, and 500 μm wavelength, to study the variation of the spectral energy distributions (SEDs) with galacto-centric distance. Methods. Detailed SED modeling is performed using azimuthally averaged fluxes in elliptical rings of 2 kpc width, out to 8 kpc galacto-centric distance. Simple isothermal and two-component grey body models, with fixed dust emissivity index, are fitted to …

Mapping Far-Ir Emission From The Central Kiloparsec Of Ngc 1097, K Sandstrom, O Krause, H Linz, E Schinnerer, G Dumas, S Meidt, H Rix, M Sauvage, F Walter, R Kennicutt, D Calzetti

Astronomy Department Faculty Publication Series

Using photometry of NGC 1097 from the Herschel PACS (Photodetector Array Camera and Spectrometer) instrument, we study the resolved properties of thermal dust continuum emission from a circumnuclear starburst ring with a radius ~900 pc. These observations are the first to resolve the structure of a circumnuclear ring at wavelengths that probe the peak (i.e. λ ~ 100 μm) of the dust spectral energy distribution. The ring dominates the far-infrared (far-IR) emission from the galaxy – the high angular resolution of PACS allows us to isolate the ring's contribution and we find it is responsible for 75, 60 and 55% …

Enhanced Dust Heating In The Bulges Of Early-Type Spiral Galaxies, C Engelbracht, L Hunt, R Skibba, J Hinz, D Calzetti

Astronomy Department Faculty Publication Series

Stellar density and bar strength should affect the temperatures of the cool (T ~ 20–30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 μm. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of …

The Afterglows Of Swift-Era Gamma-Ray Bursts. I. Comparing Pre-Swift And Swift-Era Long/Soft (Type Ii) Grb Optical Afterglows, D. A. Kann, S. Klose, B. Zhang, D. Malesani, E. Nakar, A. Pozanenko, A. C. Wilson, N. R. Butler, P. Jakobsson, S. Schulze, M. Andreev, L. A. Antonelli, I. F. Bikmaev, V. Biryukov, M. B¨Ottcher, R. A. Burenin, J. M. Castro Cer´On, A. J. Castro-Tirado, G. Chincarini, B. E. Cobb, S. Covino, P. D’Avanzo, V. D’Elia, M. Della Valle, A. De Ugarte Postigo, Yu Efimov, P. Ferrero, D. Fugazza, D. Fugazza, J. P.U. Fynbo, M. Gålfalk, F. Grundahl, J. Gorosabel, S. Gupta, S. Guziy, B. Hafizov, J. Hjorth, K. Holhjem, M. Ibrahimov, M. Im, G. L. Israel, M. Je´Linek, B. L. Jensen, R. Karimov, I. M. Khamitov, U. KizilogˇLu, E. Klunko, P. Kuba´Nek, A. S. Kutyrev, P. Laursen, A. J. Levan, F. Mannucci, C. M. Martin, A. Mescheryakov, N. Mirabal, J. P. Norris, J. -E. Ovaldsen, D. Paraficz, E. Pavlenko, S. Piranomonte, A. Rossi, V. Rumyantsev, R. Salinas, A. Sergeev, D. Sharapov, J. Sollerman, B. Stecklum, L. Stella, G. Tagliaferri, N. R. Tanvir, J. Telting, V. Testa, Adria Updike, A. Volnova, D. Watson, K. Wiersema, D. Xu

Arts & Sciences Faculty Publications

We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing …

Evidence For Supernova-Synthesized Dust From The Rising Afterglow Of Grb071025 At Z ∼ 5, Daniel A. Perley, J. S. Bloom, C. R. Klein, S. Covino, T. Minezaki, P. Wo´Zniak, W. T. Vestrand, G. G. Williams, P. Milne, N. R. Butler, Adria Updike, T. Kr¨Uhler, P. Afonso, A. Antonelli, L. Cowie, P. Ferrero, J. Greiner, D. H. Hartmann, Y. Kakazu, A. K¨Upc¨U Yoldas¸, A. N. Morgan, P. A. Price, J. X. Prochaska, Y. Yoshii

Arts & Sciences Faculty Publications

No abstract provided.

An Extended Dust Disk In A Spiral Galaxy : An Occulting Galaxy Pair In The Acs Nearby Galaxy Survey Treasury., Benne W. Holwerda, W. C. Keel, B. Williams, J. J. Dalcanton, R. S. De Jong

Faculty Scholarship

We present an analysis of an occulting galaxy pair, serendipitously discovered in the ACS Nearby Galaxy Survey Treasury observations of NGC 253 taken with the Hubble Space Telescope’s (HST) Advanced Camera for Surveys in F475W, F606W, and F814W (SDSS − g, broad V, and I). The foreground disk system (at z 0.06) shows a dusty disk much more extended than the starlight, with spiral lanes seen in extinction out to 1.5 R25, approximately 6 half-light radii. This pair is the first where extinction can be mapped reliably out to this distance from the center. The spiral arms of the extended …

Dust-Corrected Star Formation Rates Of Galaxies. I. Combinations Of H Alpha And Infrared Tracers, Rc Kennicutt, Cn Hao, D Calzetti, J Moustakas, Da Dale, G Bendo, Cw Engelbracht, Bd Johnson, Jc Lee

Astronomy Department Faculty Publication Series

We combine Hα emission-line and infrared (IR) continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to H II regions in the Spitzer Infrared Nearby Galaxies Survey, and extend the methodology to integrated measurements of galaxies. We find that our composite Hα + IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01-80 M sun yr-1) and attenuations (0-2.5 mag) studied. We find that the combination of Hα and …

Sensitivity Of Pdr Calculations To Microphysical Details, N. P. Abel, P. A. M. Van Hoof, G. Shaw, Gary J. Ferland, T. Elwert

Physics and Astronomy Faculty Publications

Our understanding of physical processes in photodissociation regions or photon-dominated regions (PDRs) largely depends on the ability of spectral synthesis codes to reproduce the observed infrared emission-line spectrum. In this paper, we explore the sensitivity of a single PDR model to microphysical details. Our calculations use the Cloudy spectral synthesis code, recently modified to include a wealth of PDR physical processes. We show how the chemical/thermal structure of a PDR, along with the calculated spectrum, changes when the treatment of physical processes such as grain physics and atomic/molecular rates are varied. We find a significant variation in the intensities of …

Agn Dusty Tori. I. Handling Of Clumpy Media, Maia Nenkova, Matthew M. Sirocky, Željko Ivezić, Moshe Elitzur

Physics and Astronomy Faculty Publications

According to unified schemes of active galactic nuclei (AGNs), the central engine is surrounded by dusty, optically thick clouds in a toroidal structure. We have recently developed a formalism that for the first time takes proper account of the clumpy nature of the AGN torus. We now provide a detailed report of our findings in a two-paper series. Here we present our general formalism for radiative transfer in clumpy media and construct its building blocks for the AGN problem-the source functions of individual dusty clouds heated by the AGN radiation field. We show that a fundamental difference from smooth density …

Silicates In Ultraluminous Infrared Galaxies, M. M. Sirocky, N. A. Levenson, Moshe Elitzur, H. W. W. Spoon, L. Armus

Physics and Astronomy Faculty Publications

We analyze the mid-infrared (MIR) spectra of ultraluminous infrared galaxies (ULIRGs) observed with the Spitzer Space Telescope's Infrared Spectrograph. Dust emission dominates the MIR spectra of ULIRGs, and the reprocessed radiation that emerges is independent of the underlying heating spectrum. Instead, the resulting emission depends sensitively on the geometric distribution of the dust, which we diagnose with comparisons of numerical simulations of radiative transfer. Quantifying the silicate emission and absorption features that appear near 10 and 18 μm requires a reliable determination of the continuum, and we demonstrate that including …

Spitzer Irs Observations Of Seyfert 1.8 And 1.9 Galaxies: A Comparison With Seyfert 1 And Seyfert 2, R. P. Deo, D. M. Crenshaw, S. B. Kraemer, M. Dietrich, Moshe Elitzur, H. Teplitz, T. J. Turner

Physics and Astronomy Faculty Publications

We present Spitzer mid-infrared spectra of 12 Seyfert 1.8 and 1.9 galaxies over the 5-38 μm region. We compare the spectral characteristics of this sample to those of 58 Seyfert 1 and 2 galaxies from the Spitzer archives. An analysis of the spectral shapes, the silicate 10 μm feature and the emission-line fluxes have enabled us to characterize the mid-IR properties of Seyfert 1.8/1.9s. We find that the EWs of the 10 μm silicate feature are generally weak in all Seyfert galaxies, as previously reported by several studies. The few Seyfert galaxies in this sample that show …

Optically Thick [O I] And [C Ii] Emission Toward Ngc 6334a, N. P. Abel, A. P. Sarma, Thomas H. Troland, Gary J. Ferland

Physics and Astronomy Faculty Publications

This work focuses on [O I] and [C II] emission toward NGC 6334A, an embedded H⁺ region/PDR only observable at infrared or longer wavelengths. A geometry in which nearly all the emission escapes out the side of the cloud facing the stars, such as Orion, is not applicable to this region. Instead, we find the geometry to be one in which the H⁺ region and associated PDR is embedded in the molecular cloud. Constant-density PDR calculations are presented which predict line intensities as a function of A_V [or N(H)], hydrogen density (n_H), and …

Dust And Pah Emission In The Star-Forming Active Nucleus Of Ngc 1097, R. E. Mason, N. A. Levenson, C. Packham, Moshe Elitzur, J. Radomski, A. O. Petric, G. S. Wright

Physics and Astronomy Faculty Publications

The nucleus of the nearby galaxy NGC 1097 is known to host a young, compact (r < 9 pc) nuclear star cluster, as well as a low-luminosity active galactic nucleus (AGN). It has been suggested both that the nuclear stellar cluster is associated with a dusty torus and that low-luminosity AGNs like NGC 1097 do not have the torus predicted by the unified model of AGNs. To investigate these contradictory possibilities we have acquired Gemini/T-ReCS 11.7 and 18.3 μm images of the central few hundred parsecs of this galaxy at <45 pc angular resolution, in which the nucleus and spectacular, kiloparsec-scale star-forming ring are detected in both bands. The small-scale mid-IR luminosity implies thermal emission from warm dust close to the central engine. Fitting of torus models shows that the observed mid-IR emission cannot be accounted for by dust heated by the central engine. Rather, the principal source heating the dust in this object is the nuclear star cluster itself, suggesting that the detected dust is not the torus of AGN unified schemes (although it is also possible that the dusty starburst itself could provide the obscuration invoked by the unified model). Comparison of Spitzer IRS and Gemini GNIRS spectra shows that, although PAH bands are strong in the immediate circumnuclear region of the galaxy, PAH emission is weak or absent in the central 19 pc. The lack of PAH emission can probably be explained largely by destruction/ionization of PAH molecules by hard photons from the nuclear star cluster. If NGC 1097 is typical, PAH emission bands may not be a useful tool with which …

Initial Mass Function Effects On The Colour Evolution Of Disk Galaxies, P. Westera, M. Samland, Stefan Kautsch, R. Buser, K. Ammon

Chemistry and Physics Faculty Articles

Aims. In this work, we want to find out if the IMF can be determined from colour images, integrated colours, or mass-to-light ratios, especially at high redshift, where galaxies cannot be resolved into individual stars, which would enable us to investigate dependencies of the IMF on cosmological epoch.

Methods. We use chemo-dynamical models to investigate the influence of the Initial Mass Function (IMF) on the evolution of a Milky Way-type disk galaxy, in particular of its colours.

Results. We find that the effect of the IMF on the internal gas absorption is larger than its effect on …

The Structure Of The Homunculus. Ii. Modeling The Physical Conditions In Η Carinae's Molecular Shell, Nathan Smith, Gary J. Ferland

Physics and Astronomy Faculty Publications

We present models that reproduce the observed double-shell structure of the Homunculus Nebula around η Carinae, including the stratification of infrared H₂ and [Fe II] emission seen in data obtained with the Phoenix spectrograph on Gemini South, as well as the corresponding stratified grain temperature seen in thermal-infrared data. Tuning the model to match the observed shell thickness allows us to determine the threshold density that permits survival of H₂. An average density of n_H~=(0.5-1)×10⁷ cm^-3 in the outer zone is required to allow H₂ to exist at all latitudes in the …

The Opacity Of Spiral Galaxy Disks. Viii. Structure Of The Cold Ism, Bw Holwerda, B Draine, Kd Gordon, Ra Gonzalez, D Calzetti, M Thornley, B Buckalew, Rj Allen, Pc Van Der Kruit

Astronomy Department Faculty Publication Series

The quantity of dust in a spiral disk can be estimated using the dust's typical emission or the extinction of a known source. In this paper we compare two techniques, one based on emission and one on absorption, applied to sections of 14 disk galaxies. The two measurements reflect, respectively, the average and apparent optical depth of a disk section. Hence, they depend differently on the average number and optical depth of ISM structures in the disk. The small-scale geometry of the cold ISM is critical for accurate models of the overall energy budget of spiral disks. ISM geometry, relative …

Gaps In The Cloud Cover? Comparing Extinction Measures In Spiral Disks, Bw Holwerda, M Meyer, M Regan, D Calzetti, Kd Gordon, Jd Smith, D Dale, Cw Engelbracht, T Jarrett, M Thornley, C Bot, B Buckalew, Rc Kennicutt, Ra Gonzalez

Astronomy Department Faculty Publication Series

Dust in galaxies can be mapped either by the FIR/submillimeter emission, the optical or infrared reddening of starlight, or the extinction of a known background source. We compare two dust extinction measurements for a set of 15 sections in 13 nearby galaxies to determine the scale of the dusty interstellar medium (ISM) responsible for disk opacity: one using stellar reddening and the other a known background source. In our earlier papers, we presented extinction measurements of 29 galaxies, based on calibrated counts of distant background objects identified though foreground disks in Hubble Space Telescope WFPC2 images. For the 13 galaxies …

Goods-Herschel Measurements Of The Dust Attenuation Of Typical Star-Forming Galaxies At High Redshift: Observations Of Uv-Selected Galaxies At Z~2, N. Reddy, M. Dickinson, D. Elbaz, G. Morrison, Mauro Giavalisco, R. Ivison, C. Papovich, D. Scott, V. Buat, D. Burgarella, V. Charmandaris, E. Daddi, G. Magdis, E. Murphy, B. Altieri, H. Aussel, H. Dannerbauer, K. Dasyra, H. S. Hwang, J. Kartaltepe, R. Leiton, B. Magnelli, P. Popesso

Mauro Giavalisco

We take advantage of the sensitivity and resolution of Herschel at 100 and 160 micron to directly image the thermal dust emission and investigate the infrared luminosities, L(IR), and dust obscuration of typical star-forming (L*) galaxies at high redshift. Our sample consists of 146 UV-selected galaxies with spectroscopic redshifts 1.51e10 Lsun at z~2 are luminous infrared galaxies (LIRGs) with a median L(IR)=(2.2+/-0.3)e11 Lsun. Typical galaxies at 1.5