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Molecular Disks in the Elliptical Galaxies NGC 83 and NGC 2320
The molecular gas in (some) early-type galaxies holds important clues tothe history and the future of these galaxies. In pursuit of these clues,we have used the BIMA millimeter array to map CO emission in the giantelliptical galaxies NGC 83 and NGC 2320 and to search for CO emissionfrom the S0 galaxy NGC 5838. We also present V and R images of NGC 83and NGC 2320 that trace their dust distributions and enable a search fordisky stellar structures. The molecular gas in NGC 83 is well relaxed,but both CO and dust in NGC 2320 show asymmetric structures that may belinked to a recent acquisition of the gas. However, the specific angularmomentum distribution of molecular gas in NGC 2320 is consistent withthat of the stars. Internal origin of the gas (stellar mass loss)cannot, therefore, be ruled out on angular momentum grounds alone. Wealso consider the evidence for star formation activity and disk growthin these two elliptical galaxies. Radio continuum and FIR fluxes of NGC83 suggest star formation activity. NGC 2320 has bright [O III]emission, but its large radio-FIR flux ratio and the mismatch betweenthe kinematics of CO and [O III] suggest that the ionized gas should notbe attributed to star formation. The origin and future of these twoCO-rich early-type galaxies are thus complex, multifaceted stories.
| Gas and Stars in an H I-Selected Galaxy Sample
We present the results of a J-band study of the H I-selected AreciboDual-Beam Survey and Arecibo Slice Survey galaxy samples using TwoMicron All Sky Survey data. We find that these galaxies span a widerange of stellar and gas properties. However, despite the diversitywithin the samples, we find a very tight correlation between luminosityand size in the J band, similar to that found in a previous paper byRosenberg & Schneider between the H I mass and size. We also findthat the correlation between the baryonic mass and the J-band diameteris even tighter than that between the baryonic mass and the rotationalvelocity.
| Cold Dust in Early-Type Galaxies. I. Observations
We describe far-infrared observations of early-type galaxies selectedfrom the Infrared Space Observatory (ISO) archive. This ratherinhomogeneous sample includes 39 giant elliptical galaxies and 14 S0 (orlater) galaxies. These galaxies were observed with the array photometerPHOT on-board the ISO satellite using a variety of different observingmodes-sparse maps, mini-maps, oversampled maps, and singlepointings-each of which requires different and often rather elaboratephotometric reduction procedures. The ISO background data agree wellwith the COBE-DIRBE results to which we have renormalized ourcalibrations. As a further check, the ISO fluxes from galaxies at 60 and100 μm agree very well with those previously observed with IRAS atthese wavelengths. The spatial resolution of ISO is several timesgreater than that of IRAS, and the ISO observations extend out to 200μm, which views a significantly greater mass of colder dust notassessable to IRAS. Most of the galaxies are essentially point sourcesat ISO resolution, but a few are clearly extended at FIR wavelengthswith image sizes that increase with FIR wavelength. The integratedfar-infrared luminosities do not correlate with optical luminosities,suggesting that the dust may have an external, merger-related origin. Ingeneral, the far-infrared spectral energy distributions can be modeledwith dust at two temperatures, ~43 and ~20 K, which probably representlimits of a continuous range of temperatures. The colder dust componentdominates the total mass of dust, 106-107Msolar, which is typically more than 10 times larger than thedust masses previously estimated for the same galaxies using IRASobservations. For S0 galaxies we find that the optically normalizedfar-infrared luminosity LFIR/LB correlatesstrongly with the mid-infrared luminosityL15μm/LB, but that correlation is weaker forelliptical galaxies.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, theNetherlands, and United Kingdom) and with the participation of ISAS andNASA.
| Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks
Long-slit stellar kinematic observations were obtained along the majoraxis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped(B/PS) bulge and six with other bulge types for comparison. Such B/PSbulges are identified in at least 45% of highly inclined systems, and agrowing body of theoretical and observational work suggests that theyare the edge-on projection of thickened bars. Profiles of the meanstellar velocity V, the velocity dispersion σ, as well as theasymmetric (h3) and symmetric (h4) deviations froma pure Gaussian are presented for all objects. Comparing these profileswith stellar kinematic bar diagnostics developed from N-bodysimulations, we find bar signatures in 24 of our sample galaxies (80%).Galaxies with a B/PS bulge typically show a double-humped rotation curvewith an intermediate dip or plateau. They also frequently show a ratherflat central velocity dispersion profile accompanied by a secondary peakor plateau, and numerous galaxies have a local central σ minimum(>~40%). The h3 profiles display up to three slopereversals. Most importantly, h3 is normally correlated with Vover the presumed bar length, contrary to expectations from axisymmetricdisks. These characteristic bar signatures strengthen the case for aclose relationship between B/PS bulges and bars and leave little roomfor other explanations of the bulges' shape. We also find thath3 is anticorrelated with V in the very center of mostgalaxies (>~60%), indicating that these objects additionally harborcold and dense decoupled (quasi-) axisymmetric central stellar disks,which may be related to the central light peaks. These central diskscoincide with previously identified star-forming ionized-gas disks(nuclear spirals) in gas-rich systems, and we argue that they formed outof gas accumulated by the bar at its center through inflow. As suggestedby N-body models, the asymmetry of the velocity profile (h3)appears to be a reliable tracer of asymmetries in disks, allowing us todiscriminate between axisymmetric and barred disks seen in projection.B/PS bulges (and thus a large fraction of all bulges) appear to be madeup mostly of disk material, which has acquired a large vertical extentthrough bar-driven vertical instabilities. Their formation is thusprobably dominated by secular evolution processes rather than merging.
| CO (3-2) Observations of Early-Type Galaxies with the Heinrich Hertz Telescope
We present Heinrich Hertz Telescope CO (3-2) observations of a sample of10 early-type galaxies detected both in far-infrared (IRAS) and in CO(1-0). Six of the objects (i.e., 60% of the sample) were detected in theCO (3-2) transition. Comparison of the beam-matched CO (3-2)/CO (1-0)and CO (2-1)/CO (1-0) intensity ratios with simple large velocitygradient and photodissociation region models reveals that early-typeobjects can be broadly classified into two categories. The majority ofobjects have a molecular interstellar medium of moderate density(nH2<=1000 cm-3) and temperature(T<=30 K). Two objects, NGC 3593 and NGC 4691, show indications ofquite denser and warmer environments, as well as gradients in theirphysical properties, compatible with their classification as starbursts.The heating source of the molecular gas and dust in all the objects inour sample appears to be ongoing star formation.
| Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
We present central velocity dispersions and Mg2 line indicesfor an all-sky sample of ~1178 elliptical and S0 galaxies, of which 984had no previous measures. This sample contains the largest set ofhomogeneous spectroscopic data for a uniform sample of ellipticalgalaxies in the nearby universe. These galaxies were observed as part ofthe ENEAR project, designed to study the peculiar motions and internalproperties of the local early-type galaxies. Using 523 repeatedobservations of 317 galaxies obtained during different runs, the dataare brought to a common zero point. These multiple observations, takenduring the many runs and different instrumental setups employed for thisproject, are used to derive statistical corrections to the data and arefound to be relatively small, typically <~5% of the velocitydispersion and 0.01 mag in the Mg2 line strength. Typicalerrors are about 8% in velocity dispersion and 0.01 mag inMg2, in good agreement with values published elsewhere.
| Redshift-Distance Survey of Early-Type Galaxies: Circular-Aperture Photometry
We present R-band CCD photometry for 1332 early-type galaxies, observedas part of the ENEAR survey of peculiar motions using early-typegalaxies in the nearby universe. Circular apertures are used to tracethe surface brightness profiles, which are then fitted by atwo-component bulge-disk model. From the fits, we obtain the structuralparameters required to estimate galaxy distances using theDn-σ and fundamental plane relations. We find thatabout 12% of the galaxies are well represented by a pure r1/4law, while 87% are best fitted by a two-component model. There are 356repeated observations of 257 galaxies obtained during different runsthat are used to derive statistical corrections and bring the data to acommon system. We also use these repeated observations to estimate ourinternal errors. The accuracy of our measurements are tested by thecomparison of 354 galaxies in common with other authors. Typical errorsin our measurements are 0.011 dex for logDn, 0.064 dex forlogre, 0.086 mag arcsec-2 for<μe>, and 0.09 for mRC,comparable to those estimated by other authors. The photometric datareported here represent one of the largest high-quality and uniformall-sky samples currently available for early-type galaxies in thenearby universe, especially suitable for peculiar motion studies.Based on observations at Cerro Tololo Inter-American Observatory (CTIO),National Optical Astronomy Observatory, which is operated by theAssociation of Universities for Research in Astronomy, Inc., undercooperative agreement with the National Science Foundation (NSF);European Southern Observatory (ESO); Fred Lawrence Whipple Observatory(FLWO); and the MDM Observatory on Kitt Peak.
| On the nature of the galaxy NGC 5666
We present B and R CCD images and optical spectroscopy in the range3700-8900 Å for the galaxy NGC 5666, which until now wasconsidered as a low-luminosity elliptical. The high-resolution imagesshow a conspicuous spiral pattern which is limited to the inner region(r <=5arcsec , or 1/6 of the isophotal radius) and a faint(presumably tidal) outer feature dotted with small knots resembling starclusters or tidal dwarf galaxies. The patchy spiral structure and theluminosity profiles suggest a late-type morphological type, but the diskis of high central surface brightness and the bulge weak and veryextended. The nuclear spectrum reveals typical emission lines found inlate-type galaxies, but the underlying nuclear stellar population andcontinuum only match that of an elliptical galaxy combined with a young(<1 Gyr) stellar population. These and other properties of the galaxysuggest that this could be a minor merger, at an intermediate stage,between a gas-rich dwarf and a small early-type disk galaxy. If this isthe case, the galaxy NGC 5666 will provide important constraints to thetheory of hierarchical galaxy formation.
| 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
| Molecular Gas in Elliptical Galaxies: Distribution and Kinematics
I present interferometric images (~7" resolution) of CO emission in fiveelliptical galaxies and nondetections in two others. These data doublethe number of elliptical galaxies whose CO emission has been fullymapped. The sample galaxies have 108 to5×109 Msolar of molecular gas distributed inmostly symmetric rotating disks with diameters of 2-12 kpc. Four out ofthe five molecular disks show remarkable alignment with the opticalmajor axes of their host galaxies. The molecular masses are a fewpercent of the total dynamical masses that are implied if the gas is oncircular orbits. If the molecular gas forms stars, it will makerotationally supported stellar disks that will be very similar incharacter to the stellar disks now known to be present in manyellipticals. Comparison of stellar kinematics to gas kinematics in NGC4476 implies that the molecular gas did not come from internal stellarmass loss because the specific angular momentum of the gas is about 3times larger than that of the stars.
| The Arecibo Dual-Beam Survey: Arecibo and VLA Observations
The Arecibo Dual-Beam Survey is a ``blind'' 21 cm search for galaxiescovering ~430 deg2 of sky. We present the data from thedetection survey as well as from the follow-up observations to confirmdetections and improve positions and flux measurements. We find 265galaxies, many of which are extremely low surface brightness. Some ofthese previously uncataloged galaxies lie within the zone of avoidance,where they are obscured by the gas and dust in our Galaxy. Eighty-one ofthese sources are not previously cataloged optically, and there are 11galaxies that have no associated optical counterpart or are onlytentatively associated with faint wisps of nebulosity on the DigitizedSky Survey images. We discuss the properties of the survey, and inparticular we make direct determinations of the completeness andreliability of the sample. The behavior of the completeness and itsdependencies is essential for determining the H I mass function. Weleave the discussion of the mass function for a later paper, but do notethat we find many low surface brightness galaxies and seven sources withMHI<108 Msolar. The AreciboObservatory is part of the National Astronomy and Ionosphere Center,which is operated by Cornell University under cooperative agreement withthe National Science Foundation. in Puerto Rico.
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| H I in Four Star-forming Low-Luminosity E/S0 and S0 Galaxies
We present H I data cubes of four low-luminosity early-type (E/S0 andS0) galaxies that are currently forming stars. These galaxies haveabsolute magnitudes in the range MB=-17.9 to -19.9(H0=50 km s-1 Mpc-1). Their H I massesrange between a few times 108 and a few times 109Msolar, and the corresponding values forMHI/LB are between 0.07 and 0.42, so these systemsare H I-rich for their morphological type. In all four galaxies, the H Iis strongly centrally concentrated with high central H I surfacedensities, in contrast to what is typically observed in more luminousearly-type galaxies. Star formation is occurring only in the centralregions. In two galaxies (NGC 802 and ESO 118-G34), the kinematics ofthe H I suggests that the gas is in a strongly warped disk, which wetake as evidence for recent accretion of H I. In the other two galaxies(NGC 2328 and ESO 027-G21), the H I must have been part of the systemsfor a considerable time. The H I properties of low-luminosity early-typegalaxies appear to be systematically different from those of many moreluminous early-type galaxies, and we suggest that these differences aredue to a different evolution of the two classes. The star formationhistory of these galaxies remains unclear. Their UBV colors and Hαemission-line strengths are consistent with having formed stars at aslowly declining rate for most of the past 1010 yr. If so,their star formation history would be intermediate between late-typespiral disks and giant elliptical galaxies. However, the current data donot rule out a small burst of recent star formation overlaid on an olderstellar population. Three of the galaxies have weak radio continuumemission, and the ratio of the far-infrared (FIR) to radio continuumemission is very similar to that of spirals of similar FIR or radioluminosity. We find that, except in the largest galaxy observed, theradio continuum emission can be accounted for solely by thermal(free-free) emission from H II regions, with no nonthermal (synchrotron)disk component. Thus, although these galaxies have gaseous disks, a diskmagnetic field may be very weak or absent. Based on observations withthe Australia Telescope Compact Array. The Australia Telescope is fundedby the Commonwealth of Australia for operation as a National Facilitymanaged by CSIRO.
| 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.
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Cool dense gas in early-type galaxies
CO observations have shown that many lenticular and elliptical galaxiescontain significant amounts of cool dense gas. This review summarizesthe observational results related to the neutral gas phase and presentsa systematic comparison with other interstellar and stellar data. Thediscovery of very dense molecular gas in the nuclear regions ofearly-type galaxies, the possible existence of a dust component neitherseen optically nor in CO, internal inconsistencies of cooling flowscenarios, the origin of the cool gas, the presence of massive stars,aspects of galaxy evolution, and possibilities for future research arediscussed in the light of the new data.
| Study of the Virgo Cluster Using the B-Band Tully-Fisher Relation
The distances to spiral galaxies of the Virgo cluster are estimatedusing the B-band Tully-Fisher (TF) relation, and the three-dimensionalstructure of the cluster is studied. The analysis is made for a completespiral sample taken from the Virgo Cluster catalog of Binggeli, Sandage,& Tammann. The sample contains virtually all spiral galaxies down toM_{BT}=-15 mag at 40 Mpc. A careful examination is made ofthe selection effect and errors of the data. We estimate distance to 181galaxies, among which distances to 89 galaxies are reasonably accurate.We compare these distances to those obtained by other authors on agalaxy-by-galaxy basis. We find reasonable consistency of theTully-Fisher distance among various authors. In particular, it is foundthat the discrepancy in the distance among the different analyses withdifferent data is about 15%, when good H I and photometric data areavailable. We clarify that the different results on the Virgo distanceamong authors arise from the choice of the sample and interpretation ofthe data. We confirm that the Tully-Fisher relation for the Virgocluster shows an unusually large scatter sigma = 0.67 mag, compared tothat for other clusters. We conclude that this scatter is not due to theintrinsic dispersion of the Tully-Fisher relation, but due to a largedepth effect of the Virgo cluster, which we estimate to be extended from12 Mpc to 30 Mpc. The distribution of H I--deficient galaxies isconcentrated at around 14--20 Mpc, indicating the presence of a core atthis distance, and this agrees with the distance estimated for M87 andother elliptical galaxies with other methods. We show also that thespatial number density of spiral galaxies takes a peak at this distance,while a simple average of all spiral galaxy distances gives 20 Mpc. Thefact that the velocity dispersion of galaxies takes a maximum at 14--18Mpc lends an additional support for the distance to the core. Thesefeatures cannot be understood if the large scatter of the TF relation ismerely due to the intrinsic dispersion. The structure of the VirgoCluster we infer from the Tully-Fisher analysis looks like a filamentwhich is familiar to us in a late phase of structure formation in thepancake collapse in hierarchical clustering simulations. This Virgofilament lies almost along the line of sight, and this is the originthat has led a number of authors to much confusion in the Virgo distancedeterminations. We show that the M87 subcluster is located around 15--18Mpc, and it consists mainly of early-type type spiral galaxies inaddition to elliptical and S0 galaxies. There are very few late-typespiral galaxies in this subcluster. The spiral rich M49 subclusterconsists of a mixture of all types of spiral galaxies and is located atabout 22 Mpc. The two other known clouds, W and M, are located at about30--40 Mpc and undergo infall toward the core. The M cloud contains fewearly type spirals. We cannot discriminate, however, whether thesesubclusters or clouds are isolated aggregates or merely parts offilamentary structure. Finally, we infer the Hubble constant to be 82+/- 10 km s-1 Mpc-1.
| 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.
| Neutral hydrogen observations of elliptical galaxies. II. The IRAS sample.
HI observations are reported for a total of 53 IRAS elliptical galaxies.Nearby confusing sources may be responsible for some of the 33detections. There are 24 isolated detected galaxies, which can be splitinto two groups, one having the same M_HI_/L_B_ ratio as the ellipticalgalaxies from the RSA (M_HI_/L_B_=0.030+/-0.026). A second group is morethan six times richer in HI (M_HI_/L_B_=0.206+/-0.105). The "HI-rich"galaxies have blue colors like spiral galaxies and have a tendencytowards higher average dust temperatures. The large number of ellipticalgalaxies in compact groups (in this sample) suggests that gravitationalinteractions and mergers may be an important source of interstellarmatter for elliptical galaxies.
| Cold dust in elliptical galaxies.
We have observed the λ1250 µm flux in 8 elliptical galaxiesusing the MPIfR 7-channel bolometer system attachet to the IRAM 30-mtelescope. Five of the galaxies are detected at more than 3σ, twoare tentatively detected and for one we obtained an upper limit. For twoof the detected galaxies, the CO(2-1) line makes a significantcontribution to the measured λ1250 µm flux. A comparison ofthe λ1250 µm fluxes, corrected for the CO(2-1) linecontribution, with IRAS 60 and 100µm data shows that there is acolt dust component (Td~<20K) in two of the ellipticals. The othergalaxies have λ1250 µm fluxes consistent with aone-temperature component, with Td typically between 20-30K.
| The molecular cloud content of early-type galaxies. V. CO in elliptical galaxies.
A survey of CO emission in 29 far-IR selected elliptical galaxiesresulted in 16 detections, of which 3 remain tentative. The moleculargas masses range from 2x10^6^Msun_ to1x10^9^Msun_, and appear to be unrelated to the underlyingstellar population. This suggests an external origin of the gas. Most ofthe elliptical galaxies with a molecular gas component have agas-to-dust mass ratio of ~700, where dust masses are derived from theIRAS fluxes, but some appear to have a ratio as low as 50. A smallapparent gas-to-dust mass ratio is also found for some late-typegalaxies, and is correlated with a low dust temperature. We suggest thata large part of the far-infrared emission from these galaxies (bothearly- and late-types) comes from dust associated with the atomic gascomponent rather than star forming regions associated with the moleculargas, and that they contain a cold dust component. Low excitationtemperatures for CO transitions in galaxies with cold dust could lead toan underestimate of the molecular gas mass by a factor of 5. The averageM_H_2__/M_HI_ ratio for the elliptical galaxies is 2-5 times lower thanfor normal spiral galaxies. Field ellipticals appear more likely tocontain an observable molecular gas component than those ellipticalsresiding in groups and clusters.
| Far-Infrared Mapping of Dusty Elliptical Galaxies
The initial results from a program to map the thermal far-infraredemission from dusty elliptical galaxies are presented. Using the Yerkes60-Channel Far-Infrared Camera on the Kuiper Airborne Observatory wehave imaged three elliptical galaxies at 160mu with a resolution of44('') (NGC 5666, NGC 6524, and the interacting system NGC 7463/4/5) andone at 100mu with a resolution of 25('') (NGC 6524). Observations of NGC1275 (Per A) are scheduled for December 1993 and may also be discussed.The E/S0 system NGC 6524 is dominated by a central point source at both100 and 160mu with a dust temperature of 29(deg) K, in agreement withIRAS data and recent submillimeter observations of the central regionsfrom the James Clark Maxwell Telescope on Mauna Kea. In addition, NGC6524 shows low-level extended dust emission at 160mu which is notdetected at 100mu . The temperature of this dust is apparently less than20(deg) K. Preliminary results from JCMT submillimeter observations ofother dusty ellipticals may also be presented. This research wassupported by NASA grant NGR 14-001-227 to the University of Chicago.
| Structure and dynamics of elliptical galaxies.
Not Available
| Infrared emission and mass loss from evolved stars in elliptical galaxies
Small aperture 10.2-micron measurements of normal elliptical galaxiesshow that for almost all of these galaxies the 12-micron emission seenby IRAS is extended on the scale of the galaxy. NGC 1052 and NGC 3998are exceptions to this; much of their 10-12-micron emission comes fromthe inner regions of the galaxies and may be associated with theiractive nuclei, as is the case for many radio galaxies. The distributionof the IR light and the IR colors of elliptical galaxies suggest thatthe most plausible source of the 12-micron emission is photospheric andcircumstellear emission from cool evolved red giant stars. The 12-micronemission is well in excess of that expected from photospheric emissionalone; about 40 percent of it probably comes from circumstellar dust.
| 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.
| Structure and dynamics of elliptical galaxies
Research on the structure and dynamics of elliptical galaxies isreviewed. Recent work on dynamical models is summarized, emphasizingtriaxial systems. The role played by observations in improvingunderstanding of the global relations, rotation, detailed kinematics,intrinsic shapes, and mass-to-light ratios of elliptical galaxies isexamined. Formation processes of elliptical galaxies are brieflyaddressed.
| Molecular gas in elliptical galaxies
C-12O(2-1) observations of 24 FIR-bright ellipticals, as well as fiveother early-type galaxies, including one FIR-faint elliptical, IC 2006,are reported. The detected ellipticals are found to have typicalmolecular gas masses of about 10 to the 7th - 10 to the 8th solarmasses, similar to their H I masses, and an approximately power-lawdistribution of M(H2)/L(B), extending to much lower values than for thespirals. The lenticular galaxies have CO properties intermediate betweenthe elliptical and spiral systems. It is concluded that theseellipticals have global interstellar medium properties similar to thosein late-type galaxies, but on a much smaller scale. A comparison of theproperties of those ellipticals which have been detected in CO with theundetected galaxies indicates that the molecular gas may occurpreferentially in the bluer, lower luminosity dwarf ellipticals, whichhave more than twice the detection rate of the brighter galaxies.
| Detection of CO emission in the elliptical galaxies NGC 3265 and NGC 5666
From observations of seven elliptical galaxies selected by the strengthof their far-infrared (FIR) fluxes, the detection of CO (2 - 1) in thecentral regions of NGC 3265 and NGC 5666, classified as E4 and Ec,respectively, is reported. Observed with the FWHM beam of 17 arcsec ofthe IRAM telescope, the CO radial velocities and line widths agree wellwith H I spectra emitted from a much more extended region, caused partlyby rigid rotation in their nuclear regions but also implying acontribution from extensive noncircular motions in the interstellar gas.The shapes of the CO profiles indicate velocity structure within thebeam. The observational ratios of CO/H I fluxes are similar to thosefound in early-type galaxies. The data also imply H2 masses of 1.7 x 10to the 8th and 3.8 x 10 to the 8th solar masses for the central regionsof NGC 3265 and NGC 5666, respectively, giving for those regions H2/H Imass ratios of about three that are comparable to what is observed forthe inner region of the Milky Way.
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