Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
The evolution of actively star-forming galaxies in the mid-infrared
In this paper we analyze the evolution of actively star-forming galaxiesin the mid-infrared (MIR). This spectral region, characterized bycontinuum emission by hot dust and by the presence of strong emissionfeatures generally ascribed to polycyclic aromatic hydrocarbon (PAH)molecules, is the most strongly affected by the heating processesassociated with star formation and/or active galactic nuclei (AGNs).Following the detailed observational characterization of galaxies in theMIR by the Infrared Space Observatory (ISO), we have updated themodelling of this spectral region in our spectrophotometric modelGRASIL. In the diffuse component we have updated the treatment of PAHsaccording to the model by Li & Draine. As for the dense phase of theinterstellar medium associated with the star-forming regions, themolecular clouds, we strongly decrease the abundance of PAHs as comparedto that in the cirrus, based on the observational evidence of the lackor weakness of PAH bands close to the newly formed stars, possibly dueto the destruction of the molecules in strong ultraviolet fields. Therobustness of the model is checked by fitting near-infrared to radiobroad-band spectra and the corresponding detailed MIR spectra of a largesample of galaxies, at once. With this model, we have analyzed thelarger sample of actively star-forming galaxies by Dale et al. We showthat the observed trends of galaxies in the ISO-IRAS-radio colour-colourplots can be interpreted in terms of the different evolutionary phasesof star formation activity, and the consequent different dominance inthe spectral energy distribution of the diffuse or dense phase of theISM. We find that the observed colours indicate a surprising homogeneityof the starburst phenomenon, allowing only a limited variation of themost important physical parameters, such as the optical depth of themolecular clouds, the time-scale of the escape of young stars from theirfor mation sites, and the gas consumption time-scale. In this paper wedo not attempt to reproduce the far-infrared coolest region in thecolour-colour plots, as we concentrate on models meant to reproduceactive star-forming galaxies, but we discuss possible requirements of amore complex modelling for the coldest objects.
| Simulating the Spitzer Mid-Infrared Color-Color Diagrams
We use a simple parameterization of the mid-IR spectra of a wide rangeof galaxy types in order to predict their distribution in the InfraredArray Camera (IRAC) 3.6, 4.5, 5.8, and 8.0 μm and MultibandPhotometer for Spitzer 24 μm color-color diagrams. We distinguishthree basic spectral types by the energetically dominant component inthe 3-12 μm regime: stellar-dominated, polycyclic aromatichydrocarbon (PAH)-dominated, and continuum-dominated. We use a Markovchain Monte Carlo approach to arrive at a more systematic and robustrepresentation of the mid-IR spectra of galaxies than do moretraditional approaches. We find that IRAC color-color plots are wellsuited to distinguishing the above spectral types, while the addition of24 μm data allows us to suggest practical three-color cuts thatpreferentially select higher redshift sources of a specific type. Wecompare our simulations with the color-color plot obtained by theSpitzer First Look Survey and find reasonable agreement. Lastly, wediscuss other applications as well as future directions for this work.
| 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).
| Infrared Emission of Normal Galaxies from 2.5 to 12 Micron: Infrared Space Observatory Spectra, Near-Infrared Continuum, and Mid-Infrared Emission Features
We present ISOPHOT spectra of the regions 2.5-4.9 μm and 5.8-11.6μm for a sample of 45 disk galaxies from the US Infrared SpaceObservatory Key Project on Normal Galaxies. The galaxies were selectedto span the range in global properties of normal, star-forming diskgalaxies in the local universe. The spectra can be decomposed into threespectral components: (1) continuum emission from stellar photospheres,which dominates the near-infrared (NIR; 2.5-4.9 μm) spectral region;(2) a weak NIR excess continuum, which has a color temperature of~103 K, carries a luminosity of a few percent of the totalfar-infrared (FIR) dust luminosity LFIR and most likelyarises from the interstellar medium (ISM); and (3) the well-known broademission features at 6.2, 7.7, 8.6, and 11.3 μm, which are generallyattributed to aromatic carbon particles. These aromatic features inemission (AFEs) dominate the mid-infrared (MIR; 5.8-11.6 μm) part ofthe spectrum and resemble the so-called type A spectra observed in manynonstellar sources and the diffuse ISM in our own Galaxy. The fewnotable exceptions include NGC 4418, where a dust continuum replaces theAFEs in MIR, and NGC 1569, where the AFEs are weak and the strongestemission feature is [S IV] 10.51 μm. The relative strengths of theAFEs vary by 15%-25% among the galaxies. However, little correlation isseen between these variations and either IRAS 60 μm/100 μm fluxdensity ratio R(60/100) or the FIR/blue luminosity ratioLFIR/LB, two widely used indicators of the currentstar formation activity, suggesting that the observed variations are nota consequence of the radiation field differences among the galaxies. Wedemonstrate that the NIR excess continuum and AFE emission arecorrelated, suggesting that they are produced by similar mechanisms andsimilar (or the same) material. On the other hand, as the current starformation activity increases, the overall strengths of the AFEs and theNIR excess continuum drop significantly with respect to that of the FIRemission from large dust grains. In particular, the summed luminosity ofthe AFEs falls from ~0.2 LFIR for the most ``IR-quiescent''galaxies to ~0.1 LFIR for the most ``IR-active'' galaxies.This is likely a consequence of the preferential destruction in intenseradiation fields of the small carriers responsible for the NIR/AFEemission.Based on observations with ISO, an ESA project with instruments fundedby ESA member states (especially the PI countries, France, Germany, theNetherlands, and the United Kingdom) and with the participation of ISASand NASA.
| COLA. II. Radio and Spectroscopic Diagnostics of Nuclear Activity in Galaxies
We present optical spectroscopic observations of 93 galaxies taken fromthe infrared-selected COLA (compact objects in low-power AGNs) sample.These are all galaxies for which we have previously obtainedlow-resolution radio observations and high-resolution (<0.05")Australian Long Baseline Array snapshots. The sample spans the range offar-IR luminosities from normal galaxies to luminous infrared galaxiesand contains a significant number of galaxies involved in galaxy-galaxyinteractions. Of the galaxies observed, 78 (84%) exhibit emission linesindicating that they are either AGNs or actively forming stars(starburst galaxies). Using a newly developed, theoretically based,optical emission line scheme to classify the spectra, we find that 15%of the emission-line galaxies are Seyfert galaxies, 77% are starbursts,and the rest are either borderline AGN/starburst or show ambiguouscharacteristics. We find little evidence for an increase in the fractionof AGNs in the sample as a function of far-IR (FIR) luminosity, incontrast to previous studies, but our sample covers only a small rangein infrared luminosity(1010.5Lsolar<=LFIR<=1011.7 Lsolar), and thus a weak trend may be masked. Instead,as the infrared luminosity increases, so does the fraction of metal-richstarbursts, objects that on more traditional diagnostic diagrams wouldhave been classified as weak, low-ionization, narrow emission lineregions. As a whole the Seyfert galaxies exhibit a small, butstatistically significant, radio excess on the radio-FIR correlationcompared to the galaxies classified as starbursts. Compact (<0.05")radio cores are detected in 55% of the Seyfert galaxies, and thesegalaxies exhibit a significantly larger radio excess than the Seyfertgalaxies in which compact cores were not detected. Our results indicatethat there may be two distinct populations of Seyfert galaxies,``radio-excess'' Seyfert galaxies, which exhibit extended radiostructures and compact radio cores, and ``radio-quiet'' Seyfertgalaxies, in which the majority of the radio emission can be attributedto star formation in the host galaxy. No significant difference is seenbetween the IR and optical spectroscopic properties of Seyfert galaxieswith and without radio cores.
| 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.
| A catalog of warps in spiral and lenticular galaxies in the Southern hemisphere
A catalog of optical warps of galaxies is presented. This can beconsidered complementary to that reported by Sánchez-Saavedra etal. (\cite{sanchez-saavedra}), with 42 galaxies in the northernhemisphere, and to that by Reshetnikov & Combes(\cite{reshetnikov99}), with 60 optical warps. The limits of the presentcatalog are: logr 25 > 0.60, B_t< 14.5, delta (2000) <0deg, -2.5 < t < 7. Therefore, lenticular galaxies havealso been considered. This catalog lists 150 warped galaxies out of asample of 276 edge-on galaxies and covers the whole southern hemisphere,except the Avoidance Zone. It is therefore very suitable for statisticalstudies of warps. It also provides a source guide for detailedparticular observations. We confirm the large frequency of warpedspirals: nearly all galaxies are warped. The frequency and warp angle donot present important differences for the different types of spirals.However, no lenticular warped galaxy has been found within the specifiedlimits. This finding constitutes an important restriction fortheoretical models.
| First Results from the COLA Project: The Radio-Far-Infrared Correlation and Compact Radio Cores in Southern COLA Galaxies
We present the first results from the COLA (compact objects in low-powerAGNs) project, which aims to determine the relationship between onefacet of AGN activity, the compact radio core, and star formation in thecircumnuclear region of the host galaxy. This will be accomplished bythe comparison of the multiwavelength properties of a sample of AGNswith compact radio cores to those of a sample of AGNs without compactcores and a matched sample of galaxies without AGNs. In this paper wediscuss the selection criteria for our galaxy samples and present theinitial radio observations of the 107 southern(δ<0deg) galaxies in our sample. Low-resolution ATCAobservations at 4.8, 2.5, and 1.4 GHz and high-resolution,single-baseline snapshots at 2.3 GHz with the Australian Long BaselineArray (LBA) are presented. We find that for the majority of the galaxiesin our sample, the radio luminosity is correlated with the far-infrared(FIR) luminosity. However, a small number of galaxies exhibit a radioexcess causing them to depart from the FIR-radio correlation. Compactradio cores are detected at fluxes greater than 1.5 mJy in nine of the105 galaxies observed with the LBA. The majority (8/9) of these galaxiesexhibit a radio excess, and 50% (7/14) of the galaxies that lie abovethe radio-FIR correlation by more than 1 σ have compact radiocores. The emission from the compact cores is too weak to account forthis radio excess, implying that there are radio structures associatedwith the compact cores that extend farther than the 0.05" resolution(corresponding to a linear scale 11-22 pc) of the LBA. There is noevidence that the radio luminosity of the compact cores is correlatedwith the FIR galaxy luminosity, indicating that the core contributeslittle to the overall FIR emission of the galaxy. The galaxies withcompact cores tend to be classified optically as AGNs, with two-thirds(6/9) exhibiting Seyfert-like optical emission line ratios, and theremaining galaxies classified either as composite objects (2/9) orstarburst (1/9). The galaxies classified optically as AGNs also exhibitthe largest radio excesses, and we therefore conclude that a large radioexcess on the radio-FIR correlation is a strong indication of an AGNwith a compact radio core.
| A Catalog of H I-Selected Galaxies from the South Celestial Cap Region of Sky
The first deep catalog of the H I Parkes All Sky Survey (HIPASS) ispresented, covering the south celestial cap (SCC) region. The SCC areais ~2400 deg2 and covers δ<-62°. The average rmsnoise for the survey is 13 mJy beam-1. Five hundredthirty-six galaxies have been cataloged according to their neutralhydrogen content, including 114 galaxies that have no previous catalogedoptical counterpart. This is the largest sample of galaxies from a blindH I survey to date. Most galaxies in optically unobscured regions of skyhave a visible optical counterpart; however, there is a small populationof low-velocity H I clouds without visible optical counterparts whoseorigins and significance are unclear. The rms accuracy of the HIPASSpositions is found to be 1.9′. The H I mass range of galaxiesdetected is from ~106 to ~1011 Msolar.There are a large number of late-type spiral galaxies in the SCC sample(66%), compared with 30% for optically selected galaxies from the sameregion in the NASA Extragalactic Database. The average ratio of H I massto B luminosity of the sample increases according to optical type, from1.8 Msolar/Lsolar for early types to 3.2Msolar/Lsolar for late-type galaxies. The HI-detected galaxies tend to follow the large-scale structure traced bygalaxies found in optical surveys. From the number of galaxies detectedin this region of sky, we predict the full HIPASS catalog will contain~5000 galaxies, to a peak flux density limit of ~39 mJy (3 σ),although this may be a conservative estimate as two large voids arepresent in the region. The H I mass function for this catalog ispresented in a subsequent paper.
| Warps and correlations with intrinsic parameters of galaxies in the visible and radio
From a comparison of the different parameters of warped galaxies in theradio, and especially in the visible, we find that: a) No large galaxy(large mass or radius) has been found to have high amplitude in thewarp, and there is no correlation of size/mass with the degree ofasymmetry of the warp. b) The disc density and the ratio of dark toluminous mass show an opposing trend: smaller values give moreasymmetric warps in the inner radii (optical warps) but show nocorrelation with the amplitude of the warp; however, in the externalradii is there no correlation with asymmetry. c) A third anticorrelationappears in a comparison of the amplitude and degree of asymmetry in thewarped galaxies. Hence, it seems that very massive dark matter haloeshave nothing to do with the formation of warps but only with the degreeof symmetry in the inner radii, and are unrelated to the warp shape forthe outermost radii. Denser discs show the same dependence.
| Far-Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the Interstellar Medium
The most important cooling lines of the neutral interstellar medium(ISM) lie in the far-infrared (FIR). We present measurements by theInfrared Space Observatory Long Wavelength Spectrometer of seven linesfrom neutral and ionized ISM of 60 normal, star-forming galaxies. Thegalaxy sample spans a range in properties such as morphology, FIR colors(indicating dust temperature), and FIR/blue ratios (indicating starformation activity and optical depth). In two-thirds of the galaxies inthis sample, the [C II] line flux is proportional to FIR dust continuum.The other one-third show a smooth decline inL[CII]/LFIR with increasing Fν(60μm)/Fν(100 μm) and LFIR/LB,spanning a range of a factor of more than 50. Two galaxies at the warmand active extreme of the range haveL[CII]/LFIR<2×10-4 (3 σupper limit). This is due to increased positive grain charge in thewarmer and more active galaxies, which leads to less efficient heatingby photoelectrons from dust grains. The ratio of the two principalphotodissociation region (PDR) cooling linesL[OI]/L[CII] shows a tight correlation withFν(60 μm)/Fν(100 μm), indicating thatboth gas and dust temperatures increase together. We derive atheoretical scaling between [N II] (122 μm) and [C II] from ionizedgas and use it to separate [C II] emission from neutral PDRs and ionizedgas. Comparison of PDR models of Kaufman et al. with observed ratios of(1) L[OI]/L[CII] and(L[CII]+L[OI])/LFIR and (2)L[OI]/LFIR and Fν(60μm)/Fν(100 μm) yields far-UV flux G0 andgas density n. The G0 and n values estimated from the twomethods agree to better than a factor of 2 and 1.5, respectively, inmore than half the sources. The derived G0 and n correlatewith each other, and G0 increases with n asG0~nα, where α~1.4 . We interpret thiscorrelation as arising from Strömgren sphere scalings if much ofthe line and continuum luminosity arises near star-forming regions. Thehigh values of PDR surface temperature (270-900 K) and pressure(6×104-1.5×107 K cm-3)derived also support the view that a significant part of grain and gasheating in the galaxies occurs very close to star-forming regions. Thedifferences in G0 and n from galaxy to galaxy may be due todifferences in the physical properties of the star-forming clouds.Galaxies with higher G0 and n have larger and/or denserstar-forming clouds.
| ISO Mid-Infrared Observations of Normal Star-Forming Galaxies: The Key Project Sample
We present mid-infrared maps and preliminary analysis for 61 galaxiesobserved with the ISOCAM instrument aboard the Infrared SpaceObservatory. Many of the general features of galaxies observed atoptical wavelengths-spiral arms, disks, rings, and bright knots ofemission-are also seen in the mid-infrared, except the prominent opticalbulges are absent at 6.75 and 15 μm. In addition, the maps are quitesimilar at 6.75 and 15 μm, except for a few cases where a centralstarburst leads to lower Iν(6.75μm)/Iν(15 μm) ratios in the inner region. We alsopresent infrared flux densities and mid-infrared sizes for thesegalaxies. The mid-infrared color Iν(6.75μm)/Iν(15 μm) shows a distinct trend with thefar-infrared color Iν(60 μm)/Iν(100μm). The quiescent galaxies in our sample [Iν(60μm)/Iν(100 μm)<~0.6] show Iν(6.75μm)/Iν(15 μm) near unity, whereas this ratio dropssignificantly for galaxies with higher global heating intensity levels.Azimuthally averaged surface brightness profiles indicate the extent towhich the mid-infrared flux is centrally concentrated, and provideinformation on the radial dependence of mid-infrared colors. Thegalaxies are mostly well resolved in these maps: almost half of themhave <10% of their flux in the central resolution element. Acomparison of optical and mid-infrared isophotal profiles indicates thatthe flux at 4400 Å near the optical outskirts of the galaxies isapproximately 8 (7) times that at 6.75 μm (15 μm), comparable toobservations of the diffuse quiescent regions of the Milky Way. Thispaper is based on observations with the Infrared Space Observatory(ISO). ISO is an ESA project with instruments funded by ESA memberstates (especially the PI countries: France, Germany, The Netherlands,and the United Kingdom) and with the participation of ISAS and NASA.
| 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
| 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.
| Redshift Distribution of Galaxies in the Southern Milky Way Region 210 degrees < L < 360 degrees and B < 15 degrees
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..107..521V&db_key=AST
| Parameters of 2447 Southern Spiral Galaxies for Use in the Tully-Fisher Relation
I-band luminosities, rotational velocities, and redshifts of 1092 spiralgalaxies have been measured by CCD photometry and Hα spectroscopyusing the 1 m and 2.3 m telescopes at Siding Spring Observatory,respectively. The results are tabulated. Luminosity profiles andHα rotation curves are given for the galaxies. When these resultsare combined with similar data for 1355 spiral galaxies publishedpreviously (Mathewson, Ford, & Buchhorn, hereafter Paper I), itprovides a large, uniform, and unique data set with which to measure,via the Tully-Fisher relation, the peculiar velocities of galaxies inthe local universe to a distance of 11,000 km s^-1^ (Mathewson &Ford). Taking advantage of the opportunity for publishing this data inmachine-readable form, in the CD-ROM, we have also included similar datafor the 1355 galaxies in Paper I.
| The IRAS Bright Galaxy Survey - Part II: Extension to Southern Declinations (delta ~< -30), and Low Galactic Latitudes (f<|b|
Complete IRAS Observations and redshifts are reported for all sourcesidentified in the IRAS Bright Galaxy Survey-Part II (hereafter referredto as BGS_2_). Source positions, radial velocities, optical magnitudes,and total flux densities, peak flux densities, and spatial extents at12, 25, and 100 ,microns are reported for 288 sources having 60 micronflux densities > 5.24 Jy, the completeness limit of the originalBright Galaxy Survey [Soifer et al., AJ, 98,766(1989)], hereafterreferred to as BGS_1_. These new data represent the extension of theIRAS Bright Galaxy Survey to southern declinations,δ<~-30^deg^, and low Galactic latitudes,5^deg^<|b|<30^deg^. Although the sky coverage of the BGS_2_ (~19935 deg^2^) is 37% larger than the sky coverage of the BGS_1_, thenumber of sources is 8% smaller due primarily to large scale structurein the local distribution of galaxies. Otherwise, the sources in theBGS_2_ show similar relationships between number counts and flux densityas observed for the 313 sources in the BGS_1_. The BGS_2_ along with theearlier BGS, represents the best sample currently available for definingthe infrared properties of galaxies in the local (z <~ 0.1) Universe.
| 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.
| A search for IRAS galaxies behind the southern Milky Way
We systematically searched for IRAS galaxies with 60 micrometer fluxdensity larger than 0.6 Jy by using the UK Schmidt Infrared and IIIa-JAtlases in the Milky Way region (absolute value of b less than 15 deg)between l = 210 deg and 360 deg. We first selected about 4000 IRAS pointsources by using our far-infrared criteria, which are optimized for thesearch of IRAS galaxies behind the Milky Way region, and then inspectedvisually the optical counterparts of them on the Schmidt Atlas filmcopies. We found 966 IRAS sources associated with galaxy-like objects.The list of the objects is presented here with the IRAS source name,Galactic coordinates, IRAS flux densities, field number and emulsion ofthe Atlas, type and size of galaxy (-like) image, redshift,multiplicity, and cross-identification. Of these, 423 galaxies arealready cataloged in the Catalog of Galaxies and Quasars Observed in theIRAS Survey, and most of the remaining 543 galaxy candidates are newlyidentified in this search. Although the radial velocities are known foronly 387 galaxies, of which 60 were newly measured by us so far, weinferred the contamination by Galactic objects to be small from the goodcorrelation between the sky distributions of the newly identified galaxycandidates and the previously cataloged galaxies. In the regions wherethe Galactic molecular clouds dominate, almost all the sources were notidentified as galaxies. The detected galaxies are clustered in the threeregions around l = 240 deg, 280 deg, and 315 deg, where the projectednumber densities are higher than the whole-sky average of IRAS galaxiesof the same flux limit.
| A southern sky survey of the peculiar velocities of 1355 spiral galaxies
The paper presents data from photometric and spectroscopic observationsof 1355 southern spiral galaxies and uses them to determine theirdistances and peculiar velocities via the Tully-Fisher (TF) relation.I-band CCD surface photometry was carried out using the 1-m and 3.9-mtelescopes at Siding Spring Observatory. H-alpha rotation curves for 965galaxies and 551 H I profiles are presented. The physical parameters,photometric and velocity data, distances, and peculiar velocities of thegalaxies are presented in tabular form. The mean distance, systemicvelocity, and average peculiar velocity of 24 clusters in the sample aregiven. TF diagrams are presented for each cluster.
| The supergalactic plane redshift survey
Redshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s.
| Neutral hydrogen observations of southern galaxies
21-cm neutral hydrogen observations, made using the 64-m Parkes radiotelescope, are presented for 48 galaxies, 39 of which are cleardetections. The HI properties and homogeneous optical data, includingnew photometry, are tabulated for the galaxies. A high signal-to-noiseratio subset of these observations is used to demonstrate that theoverall flux-density scale is within a few per cent of northern (JodrellBank, and Green Bank) scales. HI-optical diameter correlations are shownto be a useful discriminant between competing diameter systems andindicate that the Lauberts ESO(B) catalogue is the most useful currentlyavailable source of southern galaxy diameters.
| Kinematics of star forming regions
The cubic approximation of a general two-dimensional velocity field isused to study the radial velocities of 218 star forming regions up to 10kpc from the sun. It is found that departures from the Galactic circularflow are generally related to complexes of star forming regions 1-2 kpcin size. It is suggested that complexes are a consequence of clumpedstar formation and subsequent expansion of multisupernova remnants. Theresults imply that the negative departure from circular motion observedin complexes P(1)-P(4) may be due to the influence of the Perseus spiralarm.
| Southern Galaxy Catalogue.
Not Available
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
Cataloghi e designazioni:
|
NEWS@SKY (Science&Space News)
