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The multi-phase gaseous halos of star forming late-type galaxies. I. XMM-Newton observations of the hot ionized medium
This study presents first results from an X-ray mini-survey carried outwith XMM-Newton to investigate the diffuse Hot Ionized Medium in thehalos of nine nearby star-forming edge-on spiral galaxies. Diffusegaseous X-ray halos are detected in eight of our targets, covering awide range of star formation rates from quiescent to starburst cases.For four edge-on spiral galaxies, namely NGC 3044, NGC 3221, NGC 4634,and NGC 5775, we present the first published high resolution/sensitivitydetections of extended soft X-ray halos. EPIC X-ray contour mapsoverlaid onto Hα imaging data reveals that in all cases thepresence of X-ray halos is correlated with extraplanar Diffuse IonizedGas. Moreover, these halos are also associated with non-thermal cosmicray halos, as evidenced by radio continuum observations. SupplementalUV-data obtained with the OM-telescope at 210 nm show Diffuse IonizedGas to be well associated with UV emission originating in the underlyingdisk. Beside NGC 891, NGC 4634 is the second non-starburst galaxy with adiffuse soft X-ray halo (|z|≤ 4 kpc). In case of NGC 3877, for whichwe also present the first high resolution X-ray imaging data, no haloemission is detectable. EPIC pn spectra (0.3-12 keV) of the diffuseX-ray emission are extracted at different offset positions from thedisk, giving evidence to a significant decrease of gas temperatures,electron densities, and gas masses with increasing distance to theplane. A comparison between dynamical and radiative cooling time scalesimplies that the outflow in all targets is likely to be sustained. Wefind very strong indications that spatially correlated multi-phasegaseous halos are created by star forming activity in the disk plane. Ina forthcoming paper, we will present multi-frequency luminosityrelations and evaluate key parameters which might trigger the formationof multi-phase galaxy halos.
| The distribution of atomic gas and dust in nearby galaxies - III. Radial distributions and metallicity gradients
The radial distribution of dust and gas in 38 nearby galaxies isinvestigated, using a sample of galaxies for which matched resolution(25 arcsec) neutral hydrogen (HI) and 850-μm images are available.Most of these radial profiles are fitted well by an exponential model,and the derived 850-μm scalelengths are proportional to the HIscalelengths. From this relation, it is found that the metallicitygradients of these galaxies are much shallower than previous studies,unless the dust temperature is constant within the disc, or asignificant component of molecular gas exists at large radii that is nottraced by CO observations.
| Revised masses of dust and gas of SCUBA Local Universe Survey far-infrared bright galaxies based on a recent CO survey
Recent CO measurements of an essentially complete subsample of galaxiesfrom the SCUBA Local Universe Survey (SLUGS) are used to examine theirimplications for dust and gas masses in this sample. Estimates of dustmasses are affected by a contribution to the SCUBA brightnessmeasurements by CO(3-2) emission, and molecular gas masses by the use ofa modified value of the CO-to-H2 conversion factor X. Theaverage dust mass is reduced by 25-38 per cent, which has no bearing onearlier conclusions concerning the shape of the dust mass luminosityfunction derived from the SLUGS. The value of X found from the COsurvey, when applied together with the reduction in dust masses, leadsto lower estimates for the mean gas-to-dust mass ratios, where the gasincludes both H2 and H I. For the CO sample, the mean globalratio is reduced from approximately 430 to about 320-360, but is furtherreduced to values near 50 when applied to the nuclear regions relevantto the CO observations. We discuss these results and suggest that thedifferences between the nuclear and outer regions may simply reflectdifferences in metallicity or the existence of considerable amounts ofunobserved cold dust in the outer regions of these galaxies.
| Dust masses and star formation in bright IRAS galaxies. Application of a physical model for the interpretation of FIR observations
We address the problem of modeling the far-infrared (FIR) spectrum andderiving the star-formation rate (SFR) and the dust mass of spiralgalaxies. We use the realistic physical model of Popescu et al.(\cite{popescu}) to describe the overall ultra-violet (UV), optical andFIR spectral energy distribution (SED) of a spiral galaxy. The modeltakes into account the 3-dimensional old and young stellar distributionsin the bulge and the disk of a galaxy, together with the dust geometry.The geometrical characteristics of the galaxy and the intrinsic opticaland near-infrared spectra are determined by the galaxy's observed K-bandphotometry. The UV part of the spectrum is assumed to be proportional tothe SFR through the use of population synthesis models. By solving theradiative transfer equation, we are able to determine the absorbedenergy, the dust temperature and the resulting FIR spectrum. The modelhas only three free parameters: SFR, dust mass, and the fraction of theUV radiation which is absorbed locally by dense dust in the HII regions.Using this model, we are able to fit well the FIR spectra of 62 brightIRAS galaxies from the ``SCUBA Local Universe Galaxy Survey" of Dunne etal. (\cite{dunne1}). As a result, we are able to determine, amongothers, their SFR and dust mass. We find that, on average, the SFR (inabsolute units), the star-formation efficiency, the SFR surface densityand the ratio of FIR luminosity over the total intrinsic luminosity, arelarger than the respective values of typical spiral galaxies of the samemorphological type. We also find that the mean gas-to-dust mass ratio isclose to the Galactic value, while the average central face-on opticaldepth of these galaxies in the V band is 2.3. Finally, we find a strongcorrelation between SFR or dust mass and observed FIR quantities liketotal FIR luminosity or FIR luminosity at 100 and 850 μm. Thesecorrelations yield well-defined relations, which can be used todetermine a spiral galaxy's SFR and dust-mass content from FIRobservations.
| CO Molecular Gas in Infrared-luminous Galaxies
We present the first statistical survey of the properties of the12CO(1-0) and 12CO(3-2) line emission from thenuclei of a nearly complete subsample of 60 infrared (IR) luminousgalaxies selected from SCUBA Local Universe Galaxy Survey (SLUGS). Thissubsample is flux limited at S60μm>=5.24 Jy with far-IR(FIR) luminosities mostly at LFIR>1010Lsolar. We compare the emission line strengths of12CO(1-0) and (3-2) transitions at a common resolution of~15". The measured 12CO(3-2) to (1-0) line intensity ratiosr31 vary from 0.22 to 1.72, with a mean value of 0.66 for thesources observed, indicating a large spread of the degree of excitationof CO in the sample. These CO data, together with a wide range of dataat different wavelengths obtained from the literature, allow us to studythe relationship between the CO excitation conditions and the physicalproperties of gas/dust and star formation in the central regions ofgalaxies. Our analysis shows that there is a nonlinear relation betweenCO and FIR luminosities, such that their ratioLCO/LFIR decreases linearly with increasingLFIR. This behavior was found to be consistent with theSchmidt law relating star formation rate to molecular gas content, withan index N=1.4+/-0.3. We also find a possible dependence of the degreeof CO gas excitation on the efficiency of star-forming activity. Usingthe large velocity gradient (LVG) approximation to model the observeddata, we investigate the CO-to-H2 conversion factor X for theSLUGS sample. The results show that the mean value of X for the SLUGSsample is lower by a factor of 10 compared to the conventional valuederived for the Galaxy, if we assume the abundance of CO relative toH2, ZCO=10-4. For a subset of 12galaxies with H I maps, we derive a mean total face-on surface densityof H2+HI of about 42 Msolar pc-2 withinabout 2 kpc of the nucleus. This value is intermediate between that ingalaxies like our own and those with strong star formation.
| The IRAS Revised Bright Galaxy Sample
IRAS flux densities, redshifts, and infrared luminosities are reportedfor all sources identified in the IRAS Revised Bright Galaxy Sample(RBGS), a complete flux-limited survey of all extragalactic objects withtotal 60 μm flux density greater than 5.24 Jy, covering the entiresky surveyed by IRAS at Galactic latitudes |b|>5°. The RBGS includes629 objects, with median and mean sample redshifts of 0.0082 and 0.0126,respectively, and a maximum redshift of 0.0876. The RBGS supersedes theprevious two-part IRAS Bright Galaxy Samples(BGS1+BGS2), which were compiled before the final(Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGSalso makes use of more accurate and consistent automated methods tomeasure the flux of objects with extended emission. The RBGS contains 39objects that were not present in the BGS1+BGS2,and 28 objects from the BGS1+BGS2 have beendropped from RBGS because their revised 60 μm flux densities are notgreater than 5.24 Jy. Comparison of revised flux measurements forsources in both surveys shows that most flux differences are in therange ~5%-25%, although some faint sources at 12 and 25 μm differ byas much as a factor of 2. Basic properties of the RBGS sources aresummarized, including estimated total infrared luminosities, as well asupdates to cross identifications with sources from optical galaxycatalogs established using the NASA/IPAC Extragalactic Database. Inaddition, an atlas of images from the Digitized Sky Survey with overlaysof the IRAS position uncertainty ellipse and annotated scale bars isprovided for ease in visualizing the optical morphology in context withthe angular and metric size of each object. The revised bolometricinfrared luminosity function, φ(Lir), forinfrared-bright galaxies in the local universe remains best fit by adouble power law, φ(L)~Lα, withα=-0.6(+/-0.1) and α=-2.2(+/-0.1) below and above the``characteristic'' infrared luminosityL*ir~1010.5Lsolar,respectively. A companion paper provides IRAS High Resolution (HIRES)processing of over 100 RBGS sources where improved spatial resolutionoften provides better IRAS source positions or allows for deconvolutionof close galaxy pairs.
| An Hα survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge-on spiral galaxies. II. The Hα survey atlas and catalog
In this second paper on the investigation of extraplanar diffuse ionizedgas in nearby edge-on spiral galaxies we present the actual results ofthe individual galaxies of our Hα imaging survey. A grand totalof 74 galaxies have been studied, including the 9 galaxies of a recentlystudied sub-sample \citep{Ro00}. 40.5% of all studied galaxies revealextraplanar diffuse ionized gas, whereas in 59.5% of the survey galaxiesno extraplanar diffuse ionized gas could be detected. The averagedistances of this extended emission above the galactic midplane rangefrom 1-2 kpc, while individual filaments in a few galaxies reachdistances of up to |z| ~ 6 kpc. In several cases a pervasive layer ofionized gas was detected, similar to the Reynolds layer in our MilkyWay, while other galaxies reveal only extended emission locally. Themorphology of the diffuse ionized gas is discussed for each galaxy andis compared with observations of other important ISM constituents in thecontext of the disk-halo connection, in those cases where publishedresults were available. Furthermore, we present the distribution ofextraplanar dust in these galaxies, based on an analysis of theunsharp-masked R-band images. The results are compared with thedistribution of the diffuse ionized gas.Based on observations collected at the European Southern Observatory,Chile (ESO No. 63.N-0070, ESO No. 64.N-0034, ESO No. 65.N.-0002).\ref{fig22}-\ref{fig54} are only available in electronic form athttp://www.edpsciences.org
| An Hα survey aiming at the detection of extraplanar diffuse ionized gas in halos of edge-on spiral galaxies. I. How common are gaseous halos among non-starburst galaxies?
In a series of two papers we present results of a new Hα imagingsurvey, aiming at the detection of extraplanar diffuse ionized gas inhalos of late-type spiral galaxies. We have investigated a sample of 74nearby edge-on spirals, covering the northern and southern hemisphere.In 30 galaxies we detected extraplanar diffuse emission at meandistances of |z| ~ 1-2 kpc. Individual filaments can be traced out to|z|<=6 kpc in a few cases. We find a good correlation between the FIRflux ratio (S60/S100) and the SFR per unit area(LFIR/D225), based on thedetections/non-detections. This is actually valid for starburst, normaland for quiescent galaxies. A minimal SFR per unit area for the lowestS60/S100 values, at which extended emission hasbeen detected, was derived, which amounts to dotEA25thres = (3.2+/-0.5)*E40ergs-1 kpc-2. There are galaxies where extraplanaremission was detected at smaller values ofLFIR/D225, however, only in combinationwith a significantly enhanced dust temperature. The results corroboratethe general view that the gaseous halos are a direct consequence of SFactivity in the underlying galactic disk.Based on observations collected at the European Southern Observatory,Chile (ESO No. 63.N-0070, ESO No. 64.N-0034, ESO No. 65.N.-0002).
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| The distribution of atomic gas and dust in nearby galaxies - I. Presentation of matched-resolution VLA H I and SCUBA 850-μm maps
We present matched-resolution VLA HI and SCUBA 850-μm maps of 20IRAS-bright galaxies. Of the galaxies observed, two were not detected inHI and two were detected in absorption. The HI distributions of thegalaxies have a range of morphologies. Some of the systems appear HIdeficient in the central regions which could be due to a high conversionrate of HI into molecules or HI absorption. In contrast to the HI, the850-μm emission has a smooth distribution which is concentratedtowards the optical centre of each galaxy. We also find evidence for850-μm emission extending to the periphery of the optical disc insome of the galaxies. Finally, we note that the relative lack of850-μm emission when compared with HI does not necessarily mean thatthe atomic gas and dust do not have similar mass distributions.
| The SCUBA Local Universe Galaxy Survey - I. First measurements of the submillimetre luminosity and dust mass functions
This is the first of a series of papers presenting results from theSCUBA Local Universe Galaxy Survey (SLUGS), the first statistical surveyof the submillimetre properties of the local Universe. As the initialpart of this survey, we have used the SCUBA camera on the James ClerkMaxwell Telescope to observe 104 galaxies from the IRAS Bright GalaxySample. We present here the 850-μm flux measurements. The 60-, 100-,and 850-μm flux densities are well fitted by single-temperature dustspectral energy distributions, with the sample mean and standarddeviation for the best-fitting temperature beingTd=35.6+/-4.9K and for the dust emissivity indexβ=1.3+/-0.2. The dust temperature was found to correlate with60-μm luminosity. The low value of β may simply mean that thesegalaxies contain a significant amount of dust that is colder than thesetemperatures. We have estimated dust masses from the 850-μm fluxesand from the fitted temperature, although if a colder component ataround 20K is present (assuming a β of 2), then the estimated dustmasses are a factor of 1.5-3 too low. We have made the first directmeasurements of the submillimetre luminosity function (LF) and of thedust mass function. Unlike the IRAS 60-μm LF, these are well fittedby Schechter functions. The slope of the 850-μm LF at lowluminosities is steeper than -2, implying that the LF must flatten atluminosities lower than we probe here. We show that extrapolating the60-μm LF to 850μm using a single temperature and β does notreproduce the measured submillimetre LF. A population of `cold' galaxies(Td<25K) emitting strongly at submillimetre wavelengthswould have been excluded from the 60-μm-selected sample. If suchgalaxies do exist, then this estimate of the 850-μm flux is biased(it is underestimated). Whether such a population does exist is unknownat present. We correlate many of the global galaxy properties with theFIR/submillimetre properties. We find that there is a tendency for lessluminous galaxies to contain hotter dust and to have a greater starformation efficiency (cf. Young). The average gas-to-dust ratio for thesample is 581+/-43 (using both the atomic and molecular hydrogen), whichis significantly higher than the Galactic value of 160. We believe thatthis discrepancy is probably due to a `cold dust' component atTd<=20K in our galaxies. There is a surprisingly tightcorrelation between dust mass and the mass of molecular hydrogen,estimated from CO measurements, with an intrinsic scatter of ~=50percent.
| High-Resolution Radio Continuum Observations of Edge-on Spiral Galaxies
Radio continuum emission at 20 cm has been observed in a sample of 16edge-on galaxies, using the VLA in its A configuration. These galaxieswere observed recently at lower resolution by Irwin et al., who foundevidence for extraplanar disk-halo features in 15 of the 16 galaxies.Twelve of the galaxies are detected in the new high-resolutionobservations. Of these, only two, which were previously known Seyferts,show convincing evidence for AGNs. For six of the galaxies, we provideimproved positions for the galaxy nuclei. In four galaxies, radiocontinuum loops extending perpendicular to the major axis have beendiscovered, confirming previous conclusions from lower resolutionobservations that extraplanar emission is present, as well as providingfurther evidence that radio ``halos'' consist, at least in part, ofunderlying discrete features. For several galaxies, the resolution issufficient to reveal individual star-forming regions in the disk. Weexamine NGC 3556 in detail since this galaxy has been shown by King& Irwin to display extremely large H I supershells. The estimatedinput energy from supernovae in the brightest radio component of thisgalaxy is insufficient to drive the observed H I supershells. We explorepossible resolutions to this energy deficit.
| Box- and peanut-shaped bulges. I. Statistics
We present a classification for bulges of a complete sample of ~ 1350edge-on disk galaxies derived from the RC3 (Third Reference Catalogue ofBright Galaxies, de Vaucouleurs et al. \cite{rc3}). A visualclassification of the bulges using the Digitized Sky Survey (DSS) inthree types of b/p bulges or as an elliptical type is presented andsupported by CCD images. NIR observations reveal that dust extinctiondoes almost not influence the shape of bulges. There is no substantialdifference between the shape of bulges in the optical and in the NIR.Our analysis reveals that 45% of all bulges are box- and peanut-shaped(b/p). The frequency of b/p bulges for all morphological types from S0to Sd is > 40%. In particular, this is for the first time that such alarge frequency of b/p bulges is reported for galaxies as late as Sd.The fraction of the observed b/p bulges is large enough to explain theb/p bulges by bars. Partly based on observations collected at ESO/LaSilla (Chile), DSAZ/Calar Alto (Spain), and Lowell Observatory/Flagstaff(AZ/U.S.A.). Tables 6 and 7 are only available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| High-Latitude Radio Emission in a Sample of Edge-on Spiral Galaxies
We have mapped 16 edge-on galaxies at 20 cm using the Very Large Arrayin its C configuration, and a subset of these galaxies in the Dconfiguration at 6 and/or 20 cm, in a search for extended (>~1 kpc)radio continuum emission above and below the plane. For five galaxies,we could form spectral index, energy, and magnetic field maps (assumingminimum energy). While the galaxies were partly chosen by radio fluxdensity, they span a variety of star formation rates (SFRs), and onlysix might be considered ``starburst'' galaxies. A range of Hubble typeand degree of isolation are also represented. The galaxies largely fallon the FIR-radio continuum correlation. They also display a correlationbetween IR surface brightness and warmth, extending the previouslyobserved relation of Lehnert & Heckman to galaxies with lower starformation rates. We find that all but one galaxy show evidence fornonthermal high-latitude radio continuum emission, suggesting thatcosmic-ray (CR) halos are common in star-forming galaxies. Of these,eight galaxies are new detections. The high-latitude emission is seenover a variety of spatial scales and in discrete and/or smooth features.In some cases, discrete features are seen on large scales, suggestingthat smooth radio halos may consist, in part, of discrete featurescombined with low spatial resolution. In general, the discrete featuresemanate from the disk, but estimates of CR diffusion lengths suggestthat diffusion alone is insufficient to transport the particles to thehigh latitudes seen (>15 kpc in one case). Thus CRs likely diffusethrough low-density regions and/or are assisted by other mechanisms(e.g., winds). We searched for correlations between the prevalence ofhigh-latitude radio emission and a number of other properties, includingthe global SFR, supernova input rate per unit star-forming area, E_A,and environment, and do not find clear correlations with any of theseproperties. A subset of the data allows, at best, for only a weakcorrelation with E_A. Our one nondetection (NGC 4517), however, occursat a threshold level consistent with that found by Dahlem, Lisenfeld,& Golla. The lack of a good correlation with star formationindicators could be the result of the different timescales for starformation processes compared with the duration of the radio emission.Correlations with other properties, such as environment, are moredifficult to assess. However, a few isolated galaxies display strongradio halos, indicating that an interaction is not necessary to producethe extraplanar emission.
| 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 bar-enhanced star-formation activities in spiral galaxies.
We use the ratio L_FIR_/L_B_ and the IRAS color index S_25_/S_12_ (bothwidely used as indices of relative star formation rates in galaxies) toanalyse subsets (containing no known AGNs or merging/interactinggalaxies) of: (a) the IRAS Bright Galaxy Sample, (b) galaxies from theoptically complete RSA sample which have IRAS detections in all fourbands, and (c) a volume-limited IR-unselected sample. We confirm thatIR-bright barred (SB) galaxies do, on average, have very significantlyhigher values of the FIR-optical and S_25_/S_12_ ratios (and presumably,higher relative star formation rates, SFR) than that do unbarred ones;the effect is most obvious in the IR colors. We also confirm that thesedifferences are confined to early-type (S0/a-Sbc) spirals and are notevident among late-type systems (Sc-Sdm). Unlike others, we see noenhancement of the SFR in weakly-barred (SAB) galaxies. We furtherconfirm that the effect of bars on the SFR is associated with therelative IR luminosity and show that it is detectable only in galaxieswith L_FIR_/L_B_>1/3, suggesting that as soon as they have anyeffect, bars translate their host galaxies into this relativelyIR-luminous group. Conversely, for galaxies with L_FIR_/L_B_ below ~0.1this luminosity ratio is lower among barred than unbarred systems, againconfirming and quantifying an earlier result. Although there is nosimple physical relation between H I content and star formation, astrong correlation of H I content with the presence of bars has beenfound for early-type spirals with L_FIR_/L_B_>1/3. This suggests thatthe availability of fuel is the factor determining just which galaxiesundergo bar-induced starbursts.
| The FCRAO Extragalactic CO Survey. I. The Data
Emission from the CO molecule at λ = 2.6 mm has been observed at1412 positions in 300 galaxies using the 14 m telescope of the FiveCollege Radio Astronomy Observatory (HPBW = 45"); these data comprisethe FCRAO Extragalactic CO Survey. In this paper we describe the galaxysample, present the data, and determine global CO fluxes and radialdistributions for the galaxies in the Survey. Future papers will dealwith the data analysis, both with regard to the global properties ofgalaxies and the radial distributions within them. CO emission wasdetected in 236 of the 300 Survey galaxies for an overall detection rateof 79%; among the 52 Sc galaxies in the Survey, the detection rate wasas high as 96%. most of the 193 galaxies observed in multiple positionsexhibit CO distributions which peak at the center. However, a smallnumber (10-primarily Sb galaxies) exhibit CO rings at 45" resolution,and a similar number (18-primarily Sc galaxies) have CO distributionswhich peak on one side of the center. We derive CO isophotal diametersfor 151 galaxies and find the mean ratio of CO to optical isophotaldiameters to be 0.5. We also find a trend along the Hubble sequence suchthat the mean ratio of CO to optical isophotal diameters is smallestamong the early-type spirals (SO/a, Sa, and Sab) and the mean ratioincreases for Sb, Sbc, and Sc galaxies, finally decreasing among thelater types. Comparison of the global fluxes we derive for the Surveygalaxies with independent measurements from the literature indicatesthat the global fluxes we derive are accurate to ~40%.
| Multiwavelength Energy Distributions and Bolometric Luminosities of the 12 Micron Galaxy Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...453..616S&db_key=AST
| Radio Identifications of Extragalactic IRAS Sources
Extragalactic sources detected at λ= 60 microns were selectedfrom the IRAS Faint Source Catalog, Version 2 by the criterion S_60microns_ >= S_12_ microns. They were identified by positioncoincidence with radio sources stronger than 25 mJy at 4.85 GHz in the6.0 sr declination band 0^deg^ < δ < +75^deg^ (excluding the0.05 sr region 12^h^40^m^< α < 14^h^40^m^, 0^deg^<+5^deg^) and with radio sources stronger than 80 mJy in the 3.4 sr areao^h^ <α < 2o^h^, -40^deg^ < δ < 0^deg^ (plus theregion 12^h^40^m^ < α < 14^h^40^m^, 0^deg^<δ<+5^deg^). Fields containing new candidate identifications weremapped by the VLA at 4.86 GHz with about 15" FWHM resolution. Difficultcases were confirmed or rejected with the aid of accurate (σ ~ 1")radio and optical positions. The final sample of 354 identifications in{OMEGA} = 9.4 sr is reliable and large enough to contain statisticallyuseful numbers of radio-loud FIR galaxies and quasars. The logarithmicFIR radio flux ratio parameter q can be used to distinguish radiosources powered by "starbursts" from those powered by "monsters."Starbursts and normal spiral galaxies in a λ = 60 micronflux-limited sample have a narrow (σ_q_ = 0.14 +/- 0.01) qdistribution with mean = 2.74 +/- 0.01, and none have "warm"FIR spectra [α(25 microns, 60 microns) < 1.5]. The absence ofradio- quiet (but not completely silent) blazars indicates that nearlyall blazars become optically thin at frequencies v<~100 GHz.Nonthermal sources with steep FIR/optical spectra and dusty-embeddedsources visible only at FIR and radio wavelengths must be very rare.
| X-ray study of starburst galaxies.
We present full results of a wide-energy, population study of X-rayemission from a sample of 51 candidate starburst galaxies selected fromthe IRAS Bright Galaxy Sample. Superposed low and high energy X-rayemission from these galaxies in the Einstein IPC and HEAO-1 A2 and A4energy bands, which span 0.5 to 160keV, is detected at the 99.99%confidence level, after allowing for confusion noise in the HEAO-1 data.Above 13keV the confidence level is only 85%. A power-law fit to themean spectral luminosity yields a (photon) index of 1.47+/-0.26. Weconsider and assess likely environments and mechanisms for X-rayemission in starburst galaxies. These include thermal emission frommassive binaries, supernova remnants, and galactic halos, and nonthermalemission resulting from Compton scattering of relativistic electrons bythe far IR and the cosmic microwave background radiation fields. Thecontribution of the population of sources represented by this sample tothe 3-50keV residual cosmic X-ray background is estimated to be at the3-4% level assuming no evolution. This contribution is significantlyhigher if the population evolved moderately.
| A volume-limited sample of IRAS galaxies to 4000 km/s, 3: CCD photometry from Palomar and Tololo observatories
An all-sky, quasi-volume-limited sample of 251 spiral galaxies within4000 km/s has been extracted from the redshift survey of InfraredAstronomy Satellite (IRAS) galaxies by Strauss (1992). Distance modulifor these objects estimated via the Tully-Fisher (TF) method allow thepeculiar velocity field and the cosmological density parameter to beconstrained within this volume. The TF relation we exploit relatesdeprojected neutral hydrogen line width to near-infrared luminosity.Herein we present I and V band photometry for 159 members of this sampleobtained with charge coupled device (CCD) cameras at Palomar and Tololoobservatories. Image processing and photometric calibration proceduresare described. Twenty seven objects with multiple calibratedobservations suggest that isophotal I band magnitudes are reproduced toequal to or less than 0.05 mag precision at sigmaI = 23.5 magarcsec-2, and that systematic run-to-run offsets are limitedto equal to or less than 0.05 I mag.
| The extended 12 micron galaxy sample
We have selected an all-sky (absolute value of b greater than or equalto 25 deg) 12 micron flux-limited sample of 893 galaxies from the IRASFaint Source Catalog, Version 2 (FSC-2). We have obtained accurate totalfluxes in the IRAS wavebands by using the ADDSCAN procedure for allobjects with FSC-2 12 micron fluxes greater than 0.15 Jy and increasingflux densities from 12 to 60 microns, and defined the sample by imposinga survey limit of 0.22 Jy on the total 12 micron flux. Its completenessis verified, by means of the classical log N - log S andV/Vmax tests, down to 0.30 Jy, below which we have measuredthe incompleteness down to the survey limit, using the log N - log Splot, for our statistical analysis. We have obtained redshifts (mostlyfrom catalogs) for virtually all (98.4%) the galaxies in the sample.Using existing catalogs of active galaxies, we defined a subsample of118 objects consisting of 53 Seyfert 1s and quasars, 63 Seyfert 2s, andtwo blazars (approximately 13% of the full sample), which is the largestunbiased sample of Seyfert galaxies ever assembled. Since the 12 micronflux has been shown to be about one-fifth of the bolometric flux forSeyfert galaxies and quasars, the subsample of Seyferts (includingquasars and blazars) is complete not only to 0.30 Jy at 12 microns butalso with respect to a bolometric flux limit of approximately 2.0 x10-10 ergs/s/sq cm. The average value of V/Vmaxfor the full sample, corrected for incompleteness at low fluxes, is 0.51+/- 0.04, expected for a complete sample of uniformly distributedgalaxies, while the value for the Seyfert galaxy subsample is 0.46 +/-0.10. We have derived 12 microns and far-infrared luminosity functionsfor the AGNs, as well as for the entire sample. We extracted from oursample a complete subsample of 235 galaxies flux-limited (8.3 Jy) at 60microns. The 60 micron luminosity function computed for this subsampleis in satisfactory agreement with the ones derived from the brightgalaxy sample (BGS) and the deep high-galactic latitude sample, bothselected at 60 microns.
| The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.
| Radio properties of extragalactic IRAS sources
The present study identifies extragalactic sources from the IRAS FaintSource Catalog by position coincidence with radio sources stronger than25 mJy and lying north of +5 deg on the Green Bank 4.85 GHz sky maps.Published VLA maps, new 4.86 GHz VLA maps made with 15-arcsecresolution, and accurate optical positions are used to confirm 122 ofthese candidate identifications. Normal and starburst spiral galaxieswere found to comprise about 97 percent of the FIR flux-limited sample.Radio-loud 'monsters' with q less than 2.25 dominate the radio emissionfrom about 2 percent of the FIR source sample, and radio-quiet monstersare responsible for the FIR emission from less than about 1 percent ofthe FIR sample. All of the radio-identified sources are opticallyidentified, mostly with relatively bright nearby galaxies. No evidencewas found for any new populations of high-redshift FIR sources,nonthermal sources with steep FIR/optical spectra, or dust-shroudedsources visible only at FIR and radio wavelengths.
| UGC galaxies stronger than 25 mJy at 4.85 GHz
UGC galaxies in the declination band +5 to +75 deg were identified byposition coincidence with radio sources stronger than 25 mJy on theGreen Bank 4.85 GHz sky maps. Candidate identifications were confirmedor rejected with the aid of published aperture-synthesis maps and new4.86 GHz VLA maps having 15 or 18 arcsec resolution, resulting in asample of 347 nearby radio galaxies plus five new quasar-galaxy pairs.The radio energy sources in UGC galaxies were classified as 'starbursts'or 'monsters' on the basis of their infrared-radio flux ratios, infraredspectral indices, and radio morphologies. The rms scatter in thelogarithmic infrared-radio ratio q is not more than 0.16 for starburstgalaxies selected at 4.85 GHz. Radio spectral indices were obtained fornearly all of the UGC galaxies, and S0 galaxies account for adisproportionate share of the compact flat-spectrum (alpha less than0.5) radio sources. The extended radio jets and lobes produced bymonsters are preferentially, but not exclusively, aligned within about30 deg of the optical minor axes of their host galaxies. The tendencytoward minor-axis ejection appears to be independent of radio-sourcesize and is strongest for elliptical galaxies.
| An Effelsberg/VLA radio continuum survey of an optically selected sample of edge-on spiral galaxies
The results of an extensive radio continuum survey at 5 GHz with the 100m Effelsberg telescope and the Very Large Array of a large sample ofedge-on spiral galaxies (181 galaxies) are presented. The aim of thissurvey was to find candidates for more extensive studies on radio halosand on outflow phenomena from the nuclei of these galaxies.
| Magnetism in the local Virgo-centered supercluster of galaxies (radius about 24 Mpc)
The warp excess in nearby spiral galaxies is investigated as well as itsearlier interpretation in terms of a magnetic field on a distance scaleout to a redshift of 0.3 (out to 1200 Mpc, for H(0) = 75 km/s Mpc). Itis shown from a study of the rotation measure data as a function ofredshift that such a large scale is unwarranted, and that any warpexcess may be rather local and spurious with a small S/N of 1.7. It isinferred that a local intergalactic magnetic field must be less than 50microG. To facilitate studies on the local supercluster of galaxies, aVirgo-center supercluster coordinate system is proposed, where longitude0 deg goes through the center of the Virgo cluster of galaxies at thecenter of the local supercluster.
| Magnetic fields in the Milky Way neighbourhood as deduced from WARPS in spiral galaxies
It is shown that warps of spiral galaxies are not randomly oriented inthe Milky Way neighborhood. By adopting a previous model, in which warpsare produced by intergalactic magnetic fields, and considering allNorthern Hemisphere warped edge-on NGC spiral galaxies, an analysis ofthe intergalactic magnetic field in the 100 Mpc neighborhood of theGalaxy is carried out. At the 100 Mpc scale the magnetic field is stillrather homogeneous, having a direction given by (alpha = 289 deg, delta= 8 deg), but a characteristic scale of about 25 Mpc is found, insidewhich the dispersion is very low. The region containing the VirgoCluster has a direction of the magnetic field different from thedirection found in adjacent regions.
| Frequency of Warped Spiral Galaxies at Visible Wavelengths
A list of optical warped spiral galaxies with basic position andgeometrical parameters is presented. From this list an attempt todetermine the frequency of warped discs has been made. All northern NGChigh inclined spirals were examined in the Palomar Observatory SkySurvey. Warps were observed in about half of these galaxies, whichindicate that nearly all spiral galaxies are warped.
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