Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Objective Classification of Spiral Galaxies Having Extended Rotation Curves Beyond the Optical Radius
We carry out an objective classification of four samples of spiralgalaxies having extended rotation curves beyond the optical radius. Amultivariate statistical analysis (viz., principal component analysis[PCA]) shows that about 96% of the total variation is due to twocomponents, one being the combination of absolute blue magnitude andmaximum rotational velocity beyond the optical region and the otherbeing the central density of the halo. On the basis of PCA a fundamentalplane has been constructed that reduces the scatter in the Tully-Fisherrelation up to a maximum of 16%. A multiple stepwise regression analysisof the variation of the overall shape of the rotation curves shows thatit is mainly determined by the central surface brightness, while theshape purely in the outer part of the galaxy (beyond the optical radius)is mainly determined by the size of the galactic disk.
| The Baryonic Tully-Fisher Relation of Galaxies with Extended Rotation Curves and the Stellar Mass of Rotating Galaxies
I investigate the baryonic Tully-Fisher relation for a sample ofgalaxies with extended 21 cm rotation curves spanning the range 20 kms-1<~Vf<=300 km s-1. A variety ofscalings of the stellar mass-to-light ratio Υ* areconsidered. For each prescription for Υ*, I give fitsof the form Md=AVxf.Presumably, the prescription that comes closest to the correct valuewill minimize the scatter in the relation. The fit with minimum scatterhas A=50 Msolar km-4 s4 andx=4. This relation holds over five decades in mass. Galaxy color,stellar fraction, and Υ* are correlated with eachother and with Md, in the sense that more massivegalaxies tend to be more evolved. There is a systematic dependence ofthe degree of maximality of disks on surface brightness. High surfacebrightness galaxies typically have Υ*~3/4 of themaximum disk value, while low surface brightness galaxies typicallyattain ~1/4 of this amount.
| The Westerbork HI survey of spiral and irregular galaxies. III. HI observations of early-type disk galaxies
We present Hi observations of 68 early-type disk galaxies from the WHISPsurvey. They have morphological types between S0 and Sab and absoluteB-band magnitudes between -14 and -22. These galaxies form the massive,high surface-brightness extreme of the disk galaxy population, few ofwhich have been imaged in Hi before. The Hi properties of the galaxiesin our sample span a large range; the average values of MHI/LB and DH I/D25 are comparableto the ones found in later-type spirals, but the dispersions around themean are larger. No significant differences are found between the S0/S0aand the Sa/Sab galaxies. Our early-type disk galaxies follow the same Himass-diameter relation as later-type spiral galaxies, but theireffective Hi surface densities are slightly lower than those found inlater-type systems. In some galaxies, distinct rings of Hi emissioncoincide with regions of enhanced star formation, even though theaverage gas densities are far below the threshold of star formationderived by Kennicutt (1989, ApJ, 344, 685). Apparently, additionalmechanisms, as yet unknown, regulate star formation at low surfacedensities. Many of the galaxies in our sample have lopsided gasmorphologies; in most cases this can be linked to recent or ongoinginteractions or merger events. Asymmetries are rare in quiescentgalaxies. Kinematic lopsidedness is rare, both in interacting andisolated systems. In the appendix, we present an atlas of the Hiobservations: for all galaxies we show Hi surface density maps, globalprofiles, velocity fields and radial surface density profiles.
| The mass distribution in early type disk galaxies
We are studying the mass distribution in a sample of 50 early typespiral galaxies, with morphological type between S0 and Sab and absolutemagnitudes M_B between -18 and -22; they form the massive andhigh-surface brightness extreme of the disk galaxy population. Our studyis designed to investigate the relation between dark and luminous matterin these systems, of which very little yet is known.From a combination of WSRT HI observations and long-slit opticalspectra, we have obtained high-quality rotation curves. The rotationvelocities always rise very fast in the center; in the outer regions,they are often declining, with the outermost measured velocity 10-25%lower than the maximum.We decompose the rotation curves into contributions from the luminous(stellar and gaseous) and dark matter. The stellar disks and bulgesalways dominate the rotation curves within the inner few disk scalelengths, and are responsible for the decline in the outer parts. As anexample, we present here the decompositions for UGC 9133. We are able toput tight upper and lower limits on the stellar mass-to-light ratios.
| The Mass Discrepancy-Acceleration Relation: Disk Mass and the Dark Matter Distribution
The mass discrepancy in disk galaxies is shown to be well correlatedwith acceleration, increasing systematically with decreasingacceleration below a critical scalea0~3700km2s-2kpc-1=1.2×10-10ms-2.For each galaxy, there is an optimal choice of stellar mass-to-lightratio that minimizes the scatter in this mass discrepancy-accelerationrelation. The same mass-to-light ratios also minimize the scatter in thebaryonic Tully-Fisher relation and are in excellent agreement with theexpectations of stellar population synthesis. Once the disk mass isdetermined in this fashion, the dark matter distribution is specified.The circular velocity attributable to the dark matter can be expressedas a simple equation that depends only on the observed distribution ofbaryonic mass. It is a challenge to understand how this very fine-tunedcoupling between mass and light comes about.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| The far-infrared/radio correlation in the ISO era. The warm and cold far-infrared/radio correlations
We present the correlation between the far-infrared (FIR) and radioemissions from a composite sample of 72 nearby normal galaxies observedwith the ISOPHOT instrument on board the Infrared Space Observatory. Thegalaxies in the sample have measurements at three FIR wavelengths (60,100 and 170 mu m), which allowed a direct determination of the warm andcold FIR emission components. This is the first time that thecorrelation has been established for the total FIR luminosity, of whichmost is carried by the cold dust component predominantly emittinglongwards of the spectral coverage of IRAS. The slope of thiscorrelation is slightly non-linear (1.10+/- 0.03). Separate correlationsbetween the warm and cold FIR emission components and the radio emissionhave also been derived. The slope of the warm FIR/radio correlation wasfound to be linear (1.03 +/- 0.03). For the cold FIR/radio correlationwe found a slightly non-linear (1.13 +/- 0.04) slope. We qualitativelyinterpret the correlations in terms of star formation rate and find thatboth the FIR and radio emissions may be consistent with a non-lineardependence on star formation rate for galaxies not undergoing starburstactivity.Based on observations with the Infrared Space Observatory (ISO), an ESAproject with instruments funded by ESA member States (especially the PIcountries: France, Germany, The Netherlands, and the UK) and with theparticipation of ISAS and NASA.Table \ref{Tab2} and Appendices A and B are only available in electronicform at http://www.edpsciences.org
| Modified Newtonian Dynamics as an Alternative to Dark Matter
Modified Newtonian dynamics (MOND) is an empirically motivatedmodification of Newtonian gravity or inertia suggested by Milgrom as analternative to cosmic dark matter. The basic idea is that ataccelerations below ao ~ 10-8 cm/s2 ~cHo/6 the effective gravitational attraction approaches√(gnao), where gn is the usualNewtonian acceleration. This simple algorithm yields flat rotationcurves for spiral galaxies and a mass-rotation velocity relation of theform M ∝ V4 that forms the basis for the observedluminosity-rotation velocity relation-the Tully-Fisher law. We reviewthe phenomenological success of MOND on scales ranging from dwarfspheroidal galaxies to superclusters and demonstrate that the evidencefor dark matter can be equally well interpreted as evidence for MOND. Wediscuss the possible physical basis for an acceleration-basedmodification of Newtonian dynamics as well as the extention of MOND tocosmology and structure formation.
| Bar Galaxies and Their Environments
The prints of the Palomar Sky Survey, luminosity classifications, andradial velocities were used to assign all northern Shapley-Ames galaxiesto either (1) field, (2) group, or (3) cluster environments. Thisinformation for 930 galaxies shows no evidence for a dependence of barfrequency on galaxy environment. This suggests that the formation of abar in a disk galaxy is mainly determined by the properties of theparent galaxy, rather than by the characteristics of its environment.
| Complex Formation History of the Lenticular Galaxies with Stellar Counterrotation: NGC 4138 and NGC 4550
Two lenticular galaxies with counterrotating stellar components in theirdisks have been studied with the Multi-Pupil Fiber Spectrograph of the 6m telescope (at the Special Astrophysical Observatory). In NGC 4138 thenucleus is certainly chemically distinct, with the central concentrationof magnesium enhancement marginally exceeding that of iron. The ionizedgas within R=4" of the nucleus rotates circularly in an inclined ring,perhaps a kind of a circumnuclear polar ring surrounding a compactstellar minibar. NGC 4550 exhibits complex extended structures in itscenter that can be identified by enhanced levels of magnesium and ironindices; the stellar population of the unresolved nucleus is youngerthan that of the circumnuclear region. We conclude that although NGC4550 does not possess a chemically distinct nucleus in the ordinarysense of the term, there are nevertheless clear signatures of asecondary star formation burst confined perhaps to the counterrotatingstellar gaseous disk. We argue that the inclination of thecounterrotating disk differs from that of the main stellar disk,implying that the two disks are not coplanar. Both galaxies seem to havepossessed bars, either actually present or already dissolved. Partlybased on observations collected with the 6 m telescope (BTA) at theSpecial Astrophysical Observatory of the Russian Academy of Sciences.
| Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of Hαemission line of a sample of 111 spiral galaxies with recognizable andwell defined spiral morphology and with a well determined environmentalstatus, ranging from isolation to non-disruptive interaction withsatellites or companions. The form and properties of the rotation curvesare considered as a function of the isolation degree, morphological typeand luminosity. The line ratios are used to estimate the metallicity ofall the detected HII regions, thus producing a composite metallicityprofile for different types of spirals. We have found that isolatedgalaxies tend to be of later types and lower luminosity than theinteracting galaxies. The outer parts of the rotation curves of isolatedgalaxies tend to be flatter than in interacting galaxies, but they showsimilar relations between global parameters. The scatter of theTully-Fisher relation defined by isolated galaxies is significantlylower than that of interacting galaxies. The [NII]/Hα ratios, usedas a metallicity indicator, show a clear trend between Z andmorphological type, t, with earlier spirals showing higher ratios; thistrend is tighter when instead of t the gradient of the inner rotationcurve, G, is used; no trend is found with the change in interactionstatus. The Z-gradient of the disks depends on the type, being almostflat for early spirals, and increasing for later types. The[NII]/Hα ratios measured for disk HII regions of interactinggalaxies are higher than for normal/isolated objects, even if all thegalaxy families present similar distributions of Hα EquivalentWidth. Tables 3 and 4 and Figs. 6, 7 and 21 are only available inelectronic form at http://www.edpsciences.org. Table 5 is only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on dataobtained Asiago/Ekar Observatory. Also based on observations made withINT operated on the island of La Palma by ING in the SpanishObservatorio del Roque de Los Muchachos of the Instituto deAstrofísica de Canarias.
| Chemically distinct nuclei and circumnuclear rings in lenticular galaxies NGC 4429 and NGC 7013
The central regions of the regular lenticular galaxies NGC 4429 and NGC7013 have been studied with the Multi-Pupil Field (Fiber) Spectrograph(MPFS) of the 6 m telescope of the Special Astrophysical Observatory RAS(Nizhnij Arkhyz, Russia) in two spectral ranges, the blue one includingthe strong absorption lines Mg I and Fe I and the red one including theemission lines Hα and [N II]lambda 6583. We confirm the presenceof the chemically distinct nucleus in NGC 7013 reported earlier. Besidesthis unresolved (in the magnesium index) structure, we have found a ringof younger stellar populations than those in the nucleus and in thebulge; the radius of this ring is about 6\arcsec (400 pc). A similarring, distinguished by high magnesium- and iron-index values andbordered by Hα emission at its inner edge, with a radius of6\arcsec (500 pc), is found in NGC 4429. We try to relate the ringedstructure of the chemically decoupled cores in these galaxies with past,now dissolved, large-scale bars whose remnants are now seen in NGC 4429and NGC 7013 as lenses between the bulges and global disks. An analysisof the gas and star kinematics in the centers of the galaxies hasrevealed the presence of an inclined circumnuclear disk in NGC 7013 andthe existence of minibar in NGC 4429. Based on observations collectedwith the 6 m telescope of the Special Astrophysical Observatory (SAO) ofthe Russian Academy of Sciences (RAS) which is operated under thefinancial support of Science Department of Russia (registration number01-43) and on data from the HST and ING Archives.
| On the apparent coupling of neutral hydrogen and dark matter in spiral galaxies
We have studied a mass model for spiral galaxies in which the darkmatter surface density is a scaled version of the observed Hi surfacedensity. Applying this mass model to a sample of 24 spiral galaxies withreliable rotation curves, one obtains good fits for most galaxies. Thescaling factors cluster around 7, after correction for the presence ofprimordial helium. For several cases, however, different, often larger,values are found. For galaxies that cannot be fitted well, thediscrepancy occurs at large radii and results from a fairly rapiddecline of the Hi surface density in the outermost regions. Because ofsuch imperfections and in view of possible selection effects, it is notpossible to conclude here that there is a real coupling between Hi anddark matter in spiral galaxies.
| Structure and Kinematics of NGC 615 and Its Nuclear Star Formation History
The results of a complex photometric and spectral investigation of theregular Sb galaxy NGC 615 are presented. The observations were made withthe 6 m, 1 m, and 0.6 m telescopes of the Special AstrophysicalObservatory RAS (Nizhnij Arkhyz, Russia) and the 1.5 m ESO telescope (LaSilla, Chile). The analysis of the radial brightness profiles revealsthe existence of at least two decoupled exponential components; theparameters of the outer component are typical for the global disks of Sbgalaxies, and the inner component seen in the radius range 9"-30"(1.0-3.5 kpc) is distinguished by compactness and high surfacebrightness. A combination of two-dimensional velocity fields for starsand ionized gas in the central part of the galaxy and of the long-slitvelocity profiles along the major axis up to the optical border of NGC615 provides some interesting findings. In the very center, R<3" (0.3kpc), stars and gas rotate together, and the dynamical and photometricmajor axes are turned with respect to the global line of nodes; weconclude that an inclined circumnuclear disk is detected. In the bulge,R=3"-6" (0.35-0.75 kpc), the stellar velocity dispersion is more than100 km s-1, the stars rotate twice as slowly as the ionizedgas, and a counterrotating gaseous component is observed. In the innerexponential component the stars rotate together with the ionized gas,and the stellar velocity dispersion drops to about 50 km s-1.As the photometric major axis of this component is turned with respectto the line of nodes, we call it ``an oval inner disk.'' The mean age ofthe stellar populations in the nucleus and in the inner disk beyond itsH II regions is 5 Gyr, while the bulge is much older. Both thechemically decoupled nucleus of NGC 615 and the inner disk probablyformed the bulk of their more luminous stars in a secondary burst ofstar formation, perhaps provoked by the close passage of another galaxysome gigayears ago. Based on observations collected with the 6 m, 1 m,and 0.6 m telescopes of the Special Astrophysical Observatory (SAO) ofthe Russian Academy of Sciences (RAS) and with the 1.52 m ESO telescopeat La Silla.
| HI observations of loose galaxy groups. I. Data and global properties
At Nançay, 21-cm H I line observations were made of 15spiral-dominated loose groups of galaxies, divided into two samples: an``interacting'' sample containing at least one pair of interactinggalaxies, and a ``control'' sample having no optical evidence ofinteractions or morphological disturbances among the group members. Theinteracting sample consists of 62 galaxies representing 9 differentgroups, and the control sample contains 40 galaxies representing 6groups. Of the 91 galaxy and galaxy pairs observed, 74 were detected,while upper limits were placed on the remaining 17 objects. Thesehomogeneous H I data, which will be used in future analyses, providecomparative information on the H I content of groups and serve as aprobe of the vicinity of the target spirals for H I clouds or very lowsurface brightness gas-rich galaxies.
| Deep-Imaging Observations of a Candidate of an Absorbed QSO at z=0.653, AX J131831+3341
The results of deep-imaging observations of a candidate of an absorbedQSO at z=0.653, AX J131831+3341, are presented. AX J131831+3341 wasfound during the course of optical follow-up observations of the ASCALarge Sky Survey, and has an X-ray luminosity of 1045 ergs-1 (2-10 keV), which corresponds to those of QSOs. Itsoptical spectrum shows no significant broad Hβ emission line,suggesting that the object is an absorbed QSO. Deep R and V band imagesreveal the presence of a point-like nucleus and an asymmetric extendedcomponent. The nuclear component has a blue color, and the opticalmagnitude is much fainter than that expected from the observed X-rayflux for typical type-1 AGNs. These photometric properties and thepresence of broad Mg II 2800 { Angstroms} emission can be explainedsimultaneously if the observed nuclear light is dominated by scatterednuclear light, though there is a possibility that the nuclear componentis a slightly absorbed nucleus if its intrinsic X-ray to optical fluxratio is the largest among X-ray selected AGNs. The size of the extendedcomponent, which is thought to be the host galaxy of the QSO, is largerthan those of normal disk galaxies at z=0-0.75, and the absolutemagnitude is similar to those of the brightest host galaxies of QSOs atredshifts smaller than 0.5. The V-R and R-I colors of the component areconsistent with a 1 Gyr-old stellar population model without absorption.
| 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.
| Is a Simple Collisionless Relic Dark Matter Particle Ruled Out?
The central densities of dark matter (DM) halos are much lower thanpredicted in cold DM models of structure formation. Confirmation thatthey have cores with a finite central density would allow us to rule outmany popular types of collisionless particles as candidates for DM. Anymodel that leads to cusped halos (such as cold DM) is already facingserious difficulties on small scales, and hot DM models have beenexcluded. Here I show that fermionic warm DM is inconsistent with thewide range of phase-space densities in the DM halos of well-observednearby galaxies.
| The Various Kinematics of Dwarf Irregular Galaxies in Nearby Groups and Their Dark Matter Distributions
Eight dwarf irregular galaxies, in the two nearby groups of galaxiesSculptor and Centaurus A (at 2.5 Mpc and 3.5 Mpc), have been imaged inneutral hydrogen (H I) with the Australia Telescope and the Very LargeArray. These galaxies have absolute magnitudes ranging fromMB=-15.7 to -11.3. Yet they are mostly rotationallysupported, with maximum velocities going from 19 to 67 kms-1. Multicomponent mass models have been fitted to therotation curves to investigate the properties of their dark matter halosand the scaling laws of dark matter halo parameters. Dwarf galaxieshave, on average, a higher dark to luminous mass ratio, as well ashigher dark halo central densities than spiral galaxies. They have alarger dispersion of their dark matter properties both in terms of theirtotal dark matter amount and of their dark halo parameters, compared tospiral galaxies. It is therefore very difficult to predict a dwarfgalaxy rotation curve shape based only on its optical properties. Dwarfsare not well fitted by cold dark matter (CDM) halos of the type proposedby Navarro, Frenk, & White, even for ΛCDM models withΩ0 as low as 0.3. For two of our dwarfs we also haveHα rotation curves confirming the H I velocities, so thediscrepancy with the CDM models cannot be attributed to beam-smearingeffects.
| Not Available
The regular isolated Sab galaxy NGC 7217 has been studied with theMulti-Pupil Fiber Spectrograph of the 6m telescope of the SpecialAstrophysical Observatory RAS (Nizhnij Arkhyz, Russia) in two spectralranges, the blue one including the strong absorption lines Mg I and Fe Iand the red one including the emission lines Hα and [N II]lambda6583. We confirm the existence of a circumnuclear gaseous polar diskwith a radius of 3'' which we reported earlier. The same area, with aradius of 3\arcsec -4\arcsec, elongated orthogonally to the line ofnodes, is distinguished by high values of the Lick index < Fe> andshows a Mg/Fe ratio lower than solar. This implies that there were atleast two discrete star formation bursts in the circumnuclear regionwith a temporal separation of a few Gyrs. We relate this pair of burststo the complex structure of the global brightness profile of the galaxy,which may be decomposed into three exponential segments with differentscalelengths.
| The ISOPHOT 170 μ m serendipity survey. I. Compact sources with galaxy associations
The first set of compact sources observed in the ISOPHOT 170 μmSerendipity Survey is presented. From the slew data with low(I100 μm <= 15 MJy/sr) cirrus background, 115well-observed sources with a high signal-to-noise ratio in all detectorpixels having a galaxy association were extracted. Of the galaxies withknown optical morphologies, the vast majority are classified as spirals,barred spirals, or irregulars. The 170 μm fluxes measured from theSerendipity slews have been put on an absolute flux level by usingcalibration sources observed additionally with the photometric mappingmode of ISOPHOT. For all but a few galaxies, the 170 μm fluxes aredetermined for the first time, which represents a significant increasein the number of galaxies with measured Far-Infrared (FIR) fluxes beyondthe IRAS 100 μm limit. The 170 μm fluxes cover the range 2 <~F170 μm la 100 Jy. Formulae for the integrated FIR fluxesF40-220μm and the total infrared fluxesF1-1000μm incorporating the new 170 μm fluxes areprovided. The large fraction of sources with a high F170μm / F100 μm flux ratio indicates that a cold(TDust la 20 K) dust component is present in many galaxies.The detection of such a cold dust component is crucial for thedetermination of the total dust mass in galaxies, and, in cases with alarge F170 μm / F100 μm flux ratio,increases the dust mass by a significant factor. The typical mass of thecoldest dust component is MDust = 107.5 +/- 0.5Msun , a factor 2-10 larger than that derived from IRASfluxes alone. As a consequence, the majority of the derived gas-to-dustratios are much closer to the canonical value of ~ 160 for the MilkyWay. By relaxing the selection criteria, it is expected that theSerendipity Survey will eventually lead to a catalog of 170 μm fluxesfor ~ 1000 galaxies. Based on observations with ISO, an ESA project withinstruments funded by ESA Member States (especially the PI countries:France, Germany, the Netherlands and the United Kingdom) and with theparticipation of ISAS and NASA. Members of the Consortium on the ISOPHOTSerendipity Survey (CISS) are MPIA Heidelberg, ESA ISO SOC Villafranca,AIP Potsdam, IPAC Pasadena, Imperial College London.
| The QDOT all-sky IRAS galaxy redshift survey
We describe the construction of the QDOT survey, which is publiclyavailable from an anonymous FTP account. The catalogue consists ofinfrared properties and redshifts of an all-sky sample of 2387 IRASgalaxies brighter than the IRAS PSC 60-μm completeness limit(S_60>0.6Jy), sparsely sampled at a rate of one-in-six. At |b|>10deg, after removing a small number of Galactic sources, the redshiftcompleteness is better than 98per cent (2086/2127). New redshifts for1401 IRAS sources were obtained to complete the catalogue; themeasurement and reduction of these are described, and the new redshiftstabulated here. We also tabulate all sources at |b|>10 deg with noredshift so far, and sources with conflicting alternative redshiftseither from our own work, or from published velocities. A list of 95ultraluminous galaxies (i.e. with L_60μm>10^12 L_solar) is alsoprovided. Of these, ~20per cent are AGN of some kind; the broad-lineobjects typically show strong Feii emission. Since the publication ofthe first QDOT papers, there have been several hundred velocity changes:some velocities are new, some QDOT velocities have been replaced by moreaccurate values, and some errors have been corrected. We also present anew analysis of the accuracy and linearity of IRAS 60-μm fluxes. Wefind that the flux uncertainties are well described by a combination of0.05-Jy fixed size uncertainty and 8per cent fractional uncertainty.This is not enough to cause the large Malmquist-type errors in the rateof evolution postulated by Fisher et al. We do, however, find marginalevidence for non-linearity in the PSC 60-μm flux scale, in the sensethat faint sources may have fluxes overestimated by about 5per centcompared with bright sources. We update some of the previous scientificanalyses to assess the changes. The main new results are as follows. (1)The luminosity function is very well determined overall but is uncertainby a factor of several at the very highest luminosities(L_60μm>5x10^12L_solar), as this is where the remainingunidentified objects are almost certainly concentrated. (2) Thebest-fitting rate of evolution is somewhat lower than our previousestimate; expressed as pure density evolution with density varying as(1+z)^p, we find p=5.6+/-2.3. Making a rough correction for the possible(but very uncertain) non-linearity of fluxes, we find p=4.5+/-2.3. (3)The dipole amplitude decreases a little, and the implied value of thedensity parameter, assuming that IRAS galaxies trace the mass, isΩ=0.9(+0.45, -0.25). (4) Finally, the estimate of density varianceon large scales changes negligibly, still indicating a significantdiscrepancy from the predictions of simple cold dark matter cosmogonies.
| 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.
| Magnesium-to-Iron Ratio in Nuclei and Bulges of Disk Galaxies
The results of magnesium-to-iron ratio estimates are presented for thenuclei and central bulges of disk galaxies. A great variety ofbehaviours is found: the nuclei have solar Mg/Fe ratio or areMg-overabundant, the bulges can be more or less Mg-overabundant than thenuclei. But the most bulges have nearly solar Mg/Fe ratios, irrespectiveof their luminosity.
| NGC 5533: decoupled nucleus and global structure
An isolated regular Sab galaxy NGC 5533 was observed at the 6m telescopeof the Special Astrophysical Observatory RAS (Nizhnij Arkhyz, Russia)with the Multi-Pupil Field Spectrograph and scanning Fabry-Perotinterferometer and at the 1m telescope of the Special AstrophysicalObservatory through the BVRI filters with a CCD detector. Its unresolvednucleus was found to be chemically and dynamically decoupled. Thecentral mass is estimated as 3.5 x 10^9 M_Sun. The global photometricstructure reveals a presence of two disk components, the inner one beingtypical for early-type galaxies and the outer one being more extendedand with low surface brightness. An attempt is made to relate an originof the decoupled nucleus and that of the multi-tier structure of theglobal disk.
| Testing the Hypothesis of Modified Dynamics with Low Surface Brightness Galaxies and Other Evidence
The rotation curves of low surface brightness galaxies provide a uniquedata set with which to test alternative theories of gravitation over alarge dynamic range in size, mass, surface density, and acceleration.Many clearly fail, including any in which the mass discrepancy appearsat a particular length scale. One hypothesis, Modified NewtonianDynamics (MOND), is consistent with the data. Indeed, it accuratelypredicts the observed behavior. We find no evidence on any scale thatclearly contradicts MOND and much that supports it.
| Testing the Dark Matter Hypothesis with Low Surface Brightness Galaxies and Other Evidence
The severity of the mass discrepancy in spiral galaxies is stronglycorrelated with the central surface brightness of their disks.Progressively lower surface brightness galaxies have ever larger massdiscrepancies. No other parameter (luminosity, size, velocity,morphology) is so well correlated with the magnitude of the massdeficit. The rotation curves of low surface brightness disks thusprovide a unique data set with which to probe the dark matterdistribution in galaxies. The mass discrepancy is apparent from R = 0,giving a nearly direct map of the halo mass distribution. The luminousmass is insignificant. Interpreting the data in terms of dark matterleads to troublesome fine-tuning problems. Different observationsrequire contradictory amounts of dark matter. Structure formationtheories are as yet far from able to explain the observations.
| Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles
We present one of the largest homogeneous sets of spiral and lenticulargalaxy brightness profile decompositions completed to date. The 659galaxies in our sample have been fitted with a de Vaucouleurs law forthe bulge component and an inner-truncated exponential for the diskcomponent. Of the 659 galaxies in the sample, 620 were successfullyfitted with the chosen fitting functions. The fits are generally welldefined, with more than 90% having rms deviations from the observedprofile of less than 0.35 mag. We find no correlations of fittingquality, as measured by these rms residuals, with either morphologicaltype or inclination. Similarly, the estimated errors of the fittedcoefficients show no significant trends with type or inclination. Thesedecompositions form a useful basis for the study of the lightdistributions of spiral and lenticular galaxies. The object base issufficiently large that well-defined samples of galaxies can be selectedfrom it.
| Systematics of Dark Halos in High Surface Brightness Spiral Galaxies
A study of mass distributions in 22 spiral galaxies, with rotationcurves taken from the literature and Hubble types ranging from Sa to Sd,is presented. It is demonstrated that a relation of the formM_d(r)=gammaM^1/2(r)r between the mass distribution of the luminouscomponents M(r) and that of the dark halo M_d(r) is consistent with theobserved kinematics with only the dark-to-visible mass ratio displayingsignificant variations between galaxies. The parameter gamma, which iscorrelated with M_dyn/M_lum, characterizes the relative importance ofthe dark-to-luminous mass. The model M/L ratio of the stellar component,M/L_B(stars), is correlated with the observed B - V color. In our samplethe average model of Sb galaxies is 2.7 M_ȯL^-1_solar for an average color <(B - V)_0> = 0.71, that of theSc's is = 1.5 M_solar L^-1_solar for <(B -V)_0> = 0.54, both values being in very good agreement withpopulation synthesis models. A large part of the intrinsic scatter inthe Tully-Fisher relation is due to the spread in gamma. The relation ofcoupling accounts for the disk-halo conspiracy in HSB spirals and isalso valid in LSB dwarf galaxies. Its universality in disk rotatingsystems implies the existence of a physical mechanism responsible forthe continuity between visible and dark mass distributions.
| 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
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
Kataloglar ve belirtme:
|
