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Chandra Observations of Diffuse Gas and Luminous X-Ray Sources around the X-Ray-bright Elliptical Galaxy NGC 1600
We observed the X-ray-bright E3 galaxy NGC 1600 and nearby members ofthe NGC 1600 group with the Chandra X-Ray Observatory ACIS-S3 to studytheir X-ray properties. Unresolved emission dominates the observation;however, we resolved some of the emission into 71 sources, most of whichare low-mass X-ray binaries associated with NGC 1600. Twenty-one of thesources have LX>2×1039 ergss-1 (0.3-10.0 keV; assuming they are at the distance of NGC1600), marking them as ultraluminous X-ray point source (ULX)candidates; we expect that only 11+/-2 are unrelatedforeground/background sources. NGC 1600 may have the largest number ofULX candidates in an early-type galaxy to date; however, cosmic variancein the number of background active galactic nuclei cannot be ruled out.The spectrum and luminosity function (LF) of the resolved sources aremore consistent with sources found in other early-type galaxies thanwith sources found in star-forming regions of galaxies. The source LFand the spectrum of the unresolved emission both indicate that there area large number of unresolved point sources. We propose that thesesources are associated with globular clusters (GCs) and that NGC 1600has a large GC specific frequency. Observations of the GC population inNGC 1600 would be very useful for testing this prediction. Approximately50%-75% of the unresolved flux comes from diffuse gaseous emission. Thespectral fits, hardness ratios, and X-ray surface brightness profile allpoint to two gas components. We interpret the soft inner component(a<~25'', kT~0.85 keV) as the interstellar medium of NGC1600 and the hotter outer component (a>~25'', kT~1.5 keV)as the intragroup medium of the NGC 1600 group. The X-ray image showsseveral interesting structures. First, there is a central region ofexcess emission that is roughly cospatial with Hα and dustfilaments immediately west of the center of NGC 1600. There appear to beholes in the X-ray emission to the north and south of the galaxy centerthat are roughly coincident with the lobes of the NGC 1600 radio source.On larger scales, there is excess emission to the northeast, which wesuggest may indicate the center of the group potential. The group galaxyNGC 1603 shows a tail of X-ray emission to its west that is probably dueto ram pressure stripping.
| 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
| Kinematical data on early-type galaxies. V.
We present kinematical data for a sample of 26 galaxies. Rotation curvesand velocity-dispersion profiles are determined for all objects. This isour fifth paper in a series devoted to the presentation of data onelliptical and S0 galaxies, derived from long-slit absorptionspectroscopy; the series now gathers 119 galaxies with homogeneous data.Based on observations collected at the Observatoire de Haute-Provence.Tables 2 and 3 are presented in electronic form only; Tables 1 through 3are available from the CDS, Strasbourg, via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Large Stellar Disks in Small Elliptical Galaxies
We present stellar kinematics along the principal axes of sevenelliptical galaxies less luminous than M_B=-19.5, which extend beyondthe half-light radii for all systems in this photometrically selectedsample. At large radii, the kinematics not only confirm that rotationand ``diskiness'' are important in faint elliptical galaxies, as waspreviously known, but show that rotation dominates: the stars at largegalactocentric distances have (V/sigma)_max~2, similar to the disks inbona fide S0 galaxies. A comparison with published simulations ofdissipationless mergers is not straightforward. Yet, within R_e, theobserved galaxies seem to rotate somewhat faster than 3:1 mergerremnants, arguing against major mergers as the dominant mechanism in thefinal shaping of low-luminosity elliptical galaxies and favoring insteadthe dissipative formation of a disk.
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds
We present a full-sky 100 mu m map that is a reprocessed composite ofthe COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground andconfirmed point sources removed. Before using the ISSA maps, we removethe remaining artifacts from the IRAS scan pattern. Using the DIRBE 100and 240 mu m data, we have constructed a map of the dust temperature sothat the 100 mu m map may be converted to a map proportional to dustcolumn density. The dust temperature varies from 17 to 21 K, which ismodest but does modify the estimate of the dust column by a factor of 5.The result of these manipulations is a map with DIRBE qualitycalibration and IRAS resolution. A wealth of filamentary detail isapparent on many different scales at all Galactic latitudes. Inhigh-latitude regions, the dust map correlates well with maps of H Iemission, but deviations are coherent in the sky and are especiallyconspicuous in regions of saturation of H I emission toward denserclouds and of formation of H2 in molecular clouds. In contrast,high-velocity H I clouds are deficient in dust emission, as expected. Togenerate the full-sky dust maps, we must first remove zodiacal lightcontamination, as well as a possible cosmic infrared background (CIB).This is done via a regression analysis of the 100 mu m DIRBE map againstthe Leiden-Dwingeloo map of H I emission, with corrections for thezodiacal light via a suitable expansion of the DIRBE 25 mu m flux. Thisprocedure removes virtually all traces of the zodiacal foreground. Forthe 100 mu m map no significant CIB is detected. At longer wavelengths,where the zodiacal contamination is weaker, we detect the CIB atsurprisingly high flux levels of 32 +/- 13 nW m-2 sr-1 at 140 mu m andof 17 +/- 4 nW m-2 sr-1 at 240 mu m (95% confidence). This integratedflux ~2 times that extrapolated from optical galaxies in the Hubble DeepField. The primary use of these maps is likely to be as a new estimatorof Galactic extinction. To calibrate our maps, we assume a standardreddening law and use the colors of elliptical galaxies to measure thereddening per unit flux density of 100 mu m emission. We find consistentcalibration using the B-R color distribution of a sample of the 106brightest cluster ellipticals, as well as a sample of 384 ellipticalswith B-V and Mg line strength measurements. For the latter sample, weuse the correlation of intrinsic B-V versus Mg2 index to tighten thepower of the test greatly. We demonstrate that the new maps are twice asaccurate as the older Burstein-Heiles reddening estimates in regions oflow and moderate reddening. The maps are expected to be significantlymore accurate in regions of high reddening. These dust maps will also beuseful for estimating millimeter emission that contaminates cosmicmicrowave background radiation experiments and for estimating soft X-rayabsorption. We describe how to access our maps readily for general use.
| A catalogue of Mg_2 indices of galaxies and globular clusters
We present a catalogue of published absorption-line Mg_2 indices ofgalaxies and globular clusters. The catalogue is maintained up-to-datein the HYPERCAT database. The measurements are listed together with thereferences to the articles where the data were published. A codeddescription of the observations is provided. The catalogue gathers 3541measurements for 1491 objects (galaxies or globular clusters) from 55datasets. Compiled raw data for 1060 galaxies are zero-point correctedand transformed to a homogeneous system. Tables 1, 3, and 4 areavailable in electronic form only at the CDS, Strasbourg, via anonymousftp 130.79.128.5. Table 2 is available both in text and electronic form.
| 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.
| Scaleheights of 486 southern spiral galaxies and some statistical correlation
Based on Peng's method (1988), we obtain scaleheights of 486 southernspiral galaxies, the images of which are taken from the Digitized SkySurvey at Xinglong Station of Beijing Astronomical Observatory. Thefitted spiral arms of 70 galaxies are compared with their images to gettheir optimum inclinations. The scaleheights of other 416 ones arelisted in Table A1 in Appendix. After compiling and analyzing the data,we find some statistical correlations. The most interesting results arethat a flatter galaxy is bluer and looks brighter, and galaxies becomeflatter along the Hubble sequence Sab -- Scd. Based on photographic dataof the National Geographic Society -- Palomar Observatory Sky Survey(NGS-POSS) obtained using the Oschin Telescope Palomar Mountain. TheNGS-POSS was funded by a grant from the National Geographic Society tothe California Institute of Technology. The plates were processed intothe present compressed digital form with their permission. The DigitizedSky Survey was produced at the Space Telescope Science Institute underUS Government grant NAG W-2166. Table A1 is available in electronic fromonly, via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| 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.
| CCD observations linking the radio and optical references frames
Observations made with the U.S. Naval Observatory 20 cm transittelescope are presented for 104 FK5 and 13 radio stars that are directlytied into the J2000 extragalactic reference system. A comparison of thestar positions presented in this paper with the FK5 catalog findspossible warps in the FK5 reference system with amplitudes approximately0.1 arcsec and rotations for linking the optical and radio referencesystems with values omegax=-20 plus or minus 17 (s.e.),omegay=28 plus or minus 16 (s.e.), and omegaz=11plus or minus 13 (s.e.) mas. When the data of this paper are combinedwith other studies, these rotations become omegax=11 plus orminus 13 (s.e.), omegay=40 plus or minus 13 (s.e.), andomegaz=17 plus or minus 9 (s.e.) mas, indicating theomegay rotation might be real. Among the radio stars, thereare four stars (KQ Pup, 54 Cam, SZ Psc, and HD 244085) with significantoptical-radio offsets that exceed 0.15 arcsec in magnitude. Moreover,many other radio stars probably have appreciable offsets as determinedfrom a statistical investigation. Optical-radio offsets which aretypically accurate to sigma approximately plus or minus 42 (s.e.) masare also presented for 48 extragalactic objects observed with thetransit telescope. Among these objects, 21% have significant offsets.Radio galaxies are much more likely to have large offsets than QSOs andBL Lac objects, making many of them poor candidates for radio referenceobjects.
| Spectroscopy and photometry of elliptical galaxies. III - UBV aperture photometry, CCD photometry, and magnitude-related parameters
Photoelectric aperture photometry of nearly 2000 individual observationsof 449 elliptical galaxies combined with published measurements usingthe self-consistent UVB color catalog developed by Burstein et al.(1987) are presented. The data are placed on a standard magnitude andcolor system, and 'total' magnitudes and effective diameters are derivedby comparison with the standard elliptical magnitude growth curve. Agraphical representation of the standard growth curve and the residualsfrom it for each galaxy are given, and a new diameter measurement Dn ispresented which can be measured reliably for elliptical galaxies andserves as an accurate distance indicator when combined with centralvelocity dispersion. Individual magnitudes, surface brightnesses,effective diameters, and values of Dn are summarized for each galaxy incatalog form.
| Spectroscopy and photometry of elliptical galaxies. II - The spectroscopic parameters
Radial velocities, velocity dispersions, and Mg line-strength indicesare measured for 469 elliptical galaxies using four telescope/detectorconfigurations. The data have been put on a common scale; the scatter ofrepeat measurements indicates an uncertainty of + or - 10 percent and +or - 0.01 mag for single determinations of sigma and Mg2, respectively.A correction for the change in linear aperture size as a function ofdistance has been derived, and mean corrected values of sigma and Mg2are adopted. The galaxies have been assigned to groups by combining thepresent velocities with those in the redshift catalog of Huchra et al.(1983) and using the algorithm of Huchra and Geller (1982).
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