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A Spitzer Space Telescope Infrared Spectrograph Survey of Warm Molecular Hydrogen in Ultraluminous Infrared Galaxies
We have conducted a survey of ultraluminous infrared galaxies (ULIRGs)with the Infrared Spectrograph on the Spitzer Space Telescope, obtainingspectra from 5.0 to 38.5 μm for 77 sources with 0.022 Jy.The average warm molecular gas mass is ~2×108Msolar. High extinction, inferred from the 9.7 μm silicateabsorption depth, is not observed along the line of sight to themolecular gas. The derived H2 mass does not depend onF25μm/F60μm, which has been used to infereither starburst or AGN dominance. Similarly, the molecular mass doesnot scale with the 25 or 60 μm luminosities. In general, theH2 emission is consistent with an origin in photodissociationregions associated with star formation. We detect the S(0) 28.22 μmemission line in a few ULIRGs. Including this line in the model fitstends to lower the temperature by ~50-100 K, resulting in a significantincrease in the gas mass. The presence of a cooler component cannot beruled out in the remainder of our sample, for which we do not detect theS(0) line. The measured S(7) 5.51 μm line fluxes in six ULIRGsimplies ~3×106 Msolar of hot (~1400 K)H2. The warm gas mass is typically less than 1% of the coldgas mass derived from 12CO observations.Based on observations obtained with the Spitzer Space Telescope, whichis operated by the Jet Propulsion Laboratory, California Institute ofTechnology, for the National Aeronautics and Space Administration.
| Outflows in Infrared-Luminous Starbursts at z < 0.5. I. Sample, Na I D Spectra, and Profile Fitting1,
We have conducted a spectroscopic survey of 78 starburstinginfrared-luminous galaxies at redshifts up to z=0.5. We usemoderate-resolution spectroscopy of the Na I D interstellar absorptionfeature to directly probe the neutral phase of outflowing gas in thesegalaxies. Over half of our sample are ultraluminous infrared galaxiesthat are classified as starbursts; the rest have infrared luminositiesin the range log(LIR/Lsolar)=10.2-12.0. The sampleselection, observations, and data reduction are described here. Theabsorption-line spectra of each galaxy are presented. We also discussthe theory behind absorption-line fitting in the case of a partiallycovered, blended absorption doublet observed at moderate-to-highresolution, a topic neglected in the literature. A detailed analysis ofthese data is presented in a companion paper.Some of the observations reported here were obtained at the MMTObservatory, a joint facility of the Smithsonian Institution and theUniversity of Arizona.Some of the observations reported here were obtained at the Kitt PeakNational Observatory, National Optical Astronomy Observatory, which isoperated by the Association of Universities for Research in Astronomy,Inc. (AURA), under cooperative agreement with the National ScienceFoundation.
| Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Optical and Near-Infrared Imaging of the IRAS 1 Jy Sample of Ultraluminous Infrared Galaxies. I. The Atlas
An imaging survey of the IRAS 1 Jy sample of 118 ultraluminous infraredgalaxies was conducted at optical (R) and near-infrared (K')wavelengths using the University of Hawaii 2.2 m telescope. The methodsof observation and data reduction are described. An R and K'atlas of the entire sample is presented along with some of the basicastrometric and photometric parameters derived from these images. A moredetailed analysis of these data is presented in a companion paper.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Molecular Gas Depletion and Starbursts in Luminous Infrared Galaxy Mergers
Most luminous infrared galaxies (LIGs) are closely interacting/mergingsystems that are rich in molecular gas. Here we study the relationshipbetween the stage of the galaxy-galaxy interactions, the molecular gasmass, and the star formation rate as deduced from the infraredluminosity L_IR in LIGs. We find a correlation between the CO (1-0)luminosity [a measure of molecular mass M(H_2)] and the projectedseparation of merger nuclei (the indicator of merging stages) in asample of 50 LIG mergers, which shows that the molecular gas contentdecreases as merging advances. The starburst is due to enhanced starformation in preexisting molecular clouds and not to the formation ofmore molecular clouds from atomic gas. Because of the starbursts, themolecular content is being rapidly depleted as merging progresses. Thisis further supported by an anticorrelation between L_IR/M(H_2), theglobal measure of the star formation rate per unit gas mass, and theprojected separation that implies an enhanced star formation``efficiency'' in late-stage mergers compared with that of earlymergers. This is the first evidence connecting the depletion ofmolecular gas with starbursts in interacting galaxies.
| A Large Mid-Infrared Spectroscopic and Near-Infrared Imaging Survey of Ultraluminous Infrared Galaxies: Their Nature and Evolution
We present a low-resolution mid-infrared spectroscopic survey of anunbiased sample of 62 ultraluminous infrared galaxies (ULIRGs)(LIR>1012Lsolar, z<=0.3) usingISOPHOT-S on board the Infrared Space Observatory (ISO). For comparison,we also present ISOPHOT-S spectra for 23 active galactic nuclei (AGNs)and 15 starburst and normal galaxies. The line-to-continuum ratio of the7.7 μm polycyclic aromatic hydrocarbon (PAH) emission feature is usedas a discriminator between starburst and AGN activity in ULIRGs. We findthat the majority of ULIRGs are predominantly powered by starbursts. Theratio of PAH over infrared luminosities, LPAH/LIR,for starburst-dominated ULIRGs is very similar to the ratio found fortemplate starbursts. The shapes of the PAH features are sometimesunusual. Extinction has a noticeable effect on the PAH spectra of ULIRGstarbursts. We have obtained high-resolution near-infrared imaging forthe southern ISOPHOT-S ULIRGs in order to investigate their evolutionstage. The majority (68%) of the ULIRGs imaged are double systems, andall show distorted morphologies. Of the 23 double-nuclei systems, 17appear at linear separations between 4 and 14 kpc, with a meanseparation of 6.5 kpc. Using the separations measured from our newnear-infrared imaging as well as from the literature, we have examinedwhether ULIRGs that are advanced mergers are more AGN-like. We havefound no such evidence, contrary to what is postulated by the classicalevolutionary scenario. No correlation is found between the stage ofmerger in ULIRGs and their infrared luminosity. In fact, we find thatsystems in the early stages of merging may well put out maximumluminosity. We also find that the total mass of interstellar gas, asestimated from the CO (1-->0) luminosity, does not decrease withdecreasing merger separation. When both an AGN and a starburst occurconcurrently in ULIRGs, we find that the starburst dominates theluminosity output. We propose that the available gas reservoir and theindividual structure of the interacting galaxies plays a major role inthe evolution of the system. Based on observations with ISO, an ESAproject with instruments funded by ESA member states (especially the PIcountries: France, Germany, the Netherlands, and the United Kingdom)with the participation of ISAS (Japan) and NASA.
| The I-Band Tully-Fisher Relation for SC Galaxies: 21 Centimeter H I Line Data
A compilation of 21 cm line spectral parameters specifically designedfor application of the Tully-Fisher (TF) distance method is presentedfor 1201 spiral galaxies, primarily field Sc galaxies, for which opticalI-band photometric imaging is also available. New H I line spectra havebeen obtained for 881 galaxies. For an additional 320 galaxies, spectraavailable in a digital archive have been reexamined to allow applicationof a single algorithm for the derivation of the TF velocity widthparameter. A velocity width algorithm is used that provides a robustmeasurement of rotational velocity and permits an estimate of the erroron that width taking into account the effects of instrumental broadeningand signal-to-noise. The digital data are used to establish regressionrelations between measurements of velocity widths using other commonprescriptions so that comparable widths can be derived throughconversion of values published in the literature. The uniform H I linewidths presented here provide the rotational velocity measurement to beused in deriving peculiar velocities via the TF method.
| The I-Band Tully-Fisher Relation for SC Galaxies: Optical Imaging Data
Properties derived from the analysis of photometric I-band imagingobservations are presented for 1727 inclined spiral galaxies, mostly oftypes Sbc and Sc. The reduction, parameter extraction, and errorestimation procedures are discussed in detail. The asymptotic behaviorof the magnitude curve of growth and the radial variation in ellipticityand position angle are used in combination with the linearity of thesurface brightness falloff to fit the disk portion of the profile. TotalI-band magnitudes are calculated by extrapolating the detected surfacebrightness profile to a radius of eight disk scale lengths. Errors inthe magnitudes, typically ~0.04 mag, are dominated by uncertainties inthe sky subtraction and disk-fitting procedures. Comparison is made withthe similar imaging database of Mathewson, Ford, & Buchhorn, both aspresented originally by those authors and after reanalyzing theirdigital reduction files using identical disk-fitting procedures. Directcomparison is made of profile details for 292 galaxies observed incommon. Although some differences occur, good agreement is found,proving that the two data sets can be used in combination with onlyminor accommodation of those differences. The compilation of opticalproperties presented here is optimized for use in applications of theTully-Fisher relation as a secondary distance indicator in studies ofthe local peculiar velocity field.
| The Interchangeability of CO and H I in the Tully-Fisher Relation
We investigate the viability and precision of using ^12CO (J = 1 -->0) emission lines from galaxies in lieu of 21 cm emission in theTully-Fisher distance indicator (TF). Here we combine CO data gatheredspecifically for Tully-Fisher analysis with I-band photometry (both newand from the literature) for cluster galaxies between 3500 and 8000 kms^-1 and compare the luminosity-line width relation using CO with theresults of recent, large TF surveys using H i and Hα. We cull someCO data as suggested by previously published numerical simulations andfind that CO line widths, with corrections for turbulence andnoise-broadening on the order of 35 km s^-1, behave identically to H iand Hα in luminosity-line width analyses. We also examine therelation between CO line shapes and other parameters of the galaxies.
| The Molecular Interstellar Medium in Ultraluminous Infrared Galaxies
We present observations with the IRAM 30 m telescope of CO in a largesample of ultraluminous IR galaxies out to redshift z = 0.3. Most of theultraluminous galaxies in this sample are interacting, but notcompleted, mergers. The CO(1--0) luminosity of all but one of theultraluminous galaxies is high, with values of log (L^{'}_{{CO}}/{K} kms-1 pc2 ) = 9.92 +/- 0.12. The extremely small dispersion of only 30% isless than that of the far-infrared luminosity. The integrated CO lineintensity is strongly correlated with the 100 mu m flux density, asexpected for a blackbody model in which the mid- and far-IR radiation isoptically thick. We use this model to derive sizes of the FIR- andCO-emitting regions and the enclosed dynamical masses. Both the IR andCO emission originate in regions a few hundred parsecs in radius. Themedian value of L_{{FIR}}/L^{'}_{{CO}}=160 Lȯ/K km s-1 pc2, withina factor of 2 or 3 of the blackbody limit for the observed far-IRtemperatures. The entire ISM is a scaled-up version of a normal galacticdisk with the ambient densities a factor of 100 higher, making even theintercloud medium a molecular region. We compare three differenttechniques of H2 mass estimation and conclude that the ratio of gas massto CO luminosity is about a factor of 4 times lower than for giantmolecular clouds (GMCs) but that the gas mass is a large fraction of thedynamical mass. Our analysis of CO emission from ultraluminous galaxiesreduces the H2 mass from previous estimates of 2--5 x 1010 Mȯ to0.4--1.5 x 1010 Mȯ, which is in the range found for moleculargas-rich spiral galaxies. A collision involving a molecular gas-richspiral could lead to an ultraluminous galaxy powered by centralstarbursts triggered by the compression of infalling preexisting GMCs.The extremely dense molecular gas in the center of an ultraluminousgalaxy is an ideal stellar nursery for a huge starburst.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| The Local LY alpha Forest: Association of Clouds with Superclusters and Voids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...451...24S&db_key=AST
| Molecular gas mass and far-infrared emission from distant luminous galaxies
Molecular line observations suggest the central few hundred parsecs ofultraluminous IR galaxies have high mean gas densities, of about 3000 to10,000/cu cm, unlike the centers of normal galaxies and very differentfrom the disks of spiral galaxies. The CO line emission may not trace anensemble of gravitationally bound gas clouds but instead a medium boundby the total potential of the Galactic center (gas and stars). Thismeans the CO luminosity no longer measures gas mass alone, as in normalgalaxies, but instead the geometric mean of the gas mass and thedynamical mass. In practice, molecular gas dominates the dynamicalmasses of the centers of ultraluminous galaxies, which suggests gasmasses estimated from CO luminosities are basically correct. We presenta model in which the 100/micron radiation from ultraluminous galaxies isoptically thick and the CO line flux is proportional to the 100-micronflux, with S(CO)Delta(V)/S(100 microns) = 2-4 km/s. Our measurements ofCO flux from 35 ultraluminous galaxies support this model of opticallythick dust at 100 microns, providing additional evidence that the dustmass is high and the gas mass is a large fraction of the dynamical mass.We derive a relation between the M(gas)/L-prime(CO) ratio and theluminosity distance that we apply to Arp 220.
| Neutral hydrogen observations of galaxies in superclusters
Neutral hydrogen observations of spiral galaxies in the Uppsala GeneralCatalog were made with the 91 m telescope in Green Bank. Results of theH I observations are presented for 309 objects north of declination +38deg in the right ascension range between 10 h and 22 h and for a sampleof 46 objects just south of the equator in the region around R.A.between 0 h and 3 h. Many of these objects are outlying members ofsuperclusters and may be useful in the study of deviations from Hubbleflow on supercluster scales. Velocity widths as measured by fivedifferent algorithms are presented along with a profile quality index.
| The A2197 and A2199 galaxy clusters
Seventy-four new galaxy redshifts in the A2197/A2199 region arepresented. When these are added to data in the literature, 117 galaxieswith known redshifts are found within the two clusters, and 19 galaxieswith known redshifts are found generally north of A2197. These samplesare used to determine the dynamical properties and M/L ratios for thetwo clusters and to examine the broad supercluster properties of thisregion.
| Catalogue no.10 of nebulae discovered at the Warner observatory.
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