Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Optical and Near-Infrared Observations of the Peculiar Type ia Supernova 1999ac
We present 39 nights of optical photometry, 34 nights of IR photometry,and 4 nights of optical spectroscopy of the Type Ia supernova 1999ac.This supernova was discovered 2 weeks before maximum light, andobservations were begun shortly thereafter. At early times its spectraresembled the unusual SN 1999aa and were characterized by very highvelocities in the Ca II H and K lines but very low velocities in the SiII λ6355 line. The optical photometry showed a slow rise to peakbrightness but, quite peculiarly, was followed by a more rapid declinefrom maximum. Thus, the B- and V-band light curves cannot becharacterized by a single stretch factor. We argue that the best measureof the nature of this object is not the decline rate parameterΔm15(B). The B-V colors were unusual from 30 to 90 daysafter maximum light in that they evolved to bluer values at a muchslower rate than normal Type Ia supernovae. The spectra and bolometriclight curve indicate that this event was similar to thespectroscopically peculiar slow decliner SN 1999aa.Based in part on observations taken at the Cerro Tololo Inter-AmericanObservatory, National Optical Astronomy Observatory, which is operatedby the Association of Universities for Research in Astronomy (AURA),Inc., under cooperative agreement with the National Science Foundation.This paper is also based in part on observations obtained with theApache Point Observatory 3.5 m telescope, which is owned and operated bythe Astrophysical Research Consortium.
| UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observedfrom 1997 to 2001 as part of a continuing monitoring campaign at theFred Lawrence Whipple Observatory of the Harvard-Smithsonian Center forAstrophysics. The data set comprises 2190 observations and is thelargest homogeneously observed and reduced sample of SNe Ia to date,nearly doubling the number of well-observed, nearby SNe Ia withpublished multicolor CCD light curves. The large sample of U-bandphotometry is a unique addition, with important connections to SNe Iaobserved at high redshift. The decline rate of SN Ia U-band light curvescorrelates well with the decline rate in other bands, as does the U-Bcolor at maximum light. However, the U-band peak magnitudes show anincreased dispersion relative to other bands even after accounting forextinction and decline rate, amounting to an additional ~40% intrinsicscatter compared to the B band.
| Chemistry and Star Formation in the Host Galaxies of Type Ia Supernovae
We study the effect of environment on the properties of Type Iasupernovae by analyzing the integrated spectra of 57 local Type Iasupernova host galaxies. We deduce from the spectra the metallicity,current star formation rate, and star formation history of the host andcompare these to the supernova decline rates. Additionally, we comparethe host properties to the difference between the derived supernovadistance and the distance determined from the best-fit Hubble law. Fromthis we investigate possible uncorrected systematic effects inherent inthe calibration of Type Ia supernova luminosities using light-curvefitting techniques. Our results indicate a statistically insignificantcorrelation in the direction of higher metallicity spiral galaxieshosting fainter Type Ia supernovae. However, we present qualitativeevidence suggesting that progenitor age is more likely to be the sourceof variability in supernova peak luminosities than is metallicity. We donot find a correlation between the supernova decline rate and hostgalaxy absolute B magnitude, nor do we find evidence of a significantrelationship between decline rate and current host galaxy star formationrate. A tenuous correlation is observed between the supernova Hubbleresiduals and host galaxy metallicities. Further host galaxyobservations will be needed to refine the significance of this result.Finally, we characterize the environmental property distributions forType Ia supernova host galaxies through a comparison with two larger,more general galaxy distributions using Kolmogorov-Smirnov tests. Theresults show the host galaxy metallicity distribution to be similar tothe metallicity distributions of the galaxies of the NFGS and SDSS.Significant differences are observed between the SN Ia distributions ofabsolute B magnitude and star formation histories and the correspondingdistributions of galaxies in the NFGS and SDSS. Among these is an abruptupper limit observed in the distribution of star formation histories ofthe host galaxy sample, suggesting a Type Ia supernovae characteristicdelay time lower limit of approximately 2.0 Gyr. Other distributiondiscrepancies are investigated and the effects on the supernovaproperties are discussed.
| Reddening, Absorption, and Decline Rate Corrections for a Complete Sample of Type Ia Supernovae Leading to a Fully Corrected Hubble Diagram to v < 30,000 km s-1
Photometric (BVI) and redshift data corrected for streaming motions arecompiled for 111 ``Branch-normal,'' four 1991T-like, seven 1991bg-like,and two unusual supernovae of Type Ia (SNe Ia). Color excessesE(B-V)host of normal SNe Ia, due to the absorption of thehost galaxy, are derived by three independent methods, giving excellentagreement leading to the intrinsic colors at maximum of(B-V)00=-0.024+/-0.010 and (V-I)00=-0.265+/-0.016if normalized to a common decline rate of Δm15=1.1. Thestrong correlation between redshift absolute magnitudes (based on anarbitrary Hubble constant of H0=60 km s-1Mpc-1), corrected only for the extrinsic Galactic absorption,and the derived E(B-V)host color excesses leads to thewell-determined yet abnormal absorption-to-reddening ratios ofRBVI=3.65+/-0.16, 2.65+/-0.15, and 1.35+/-0.21.Comparison with the canonical Galactic values of 4.1, 3.1, and 1.8forces the conclusion that the law of interstellar absorption in thepath length to the SN in the host galaxy is different from the localGalactic law, a result consistent with earlier conclusions by others.Improved correlations of the fully corrected absolute magnitudes (on thesame arbitrary Hubble constant zero point) with host galaxymorphological type, decline rate, and intrinsic color are derived. Werecover the result that SNe Ia in E/S0 galaxies are ~0.3 mag fainterthan in spiral galaxies for possible reasons discussed in the text. Thenew decline rate corrections to absolute magnitudes are smaller thanthose by some authors for reasons explained in the text. The fourspectroscopically peculiar 1991T-type SNe are significantly overluminousas compared to Branch-normal SNe Ia. The overluminosity of the seven1999aa-like SNe is less pronounced. The seven 1991bg types in the sampleconstitute a separate class of SNe Ia, averaging in B 2 mag fainter thanthe normal Ia. New Hubble diagrams in B, V, and I are derived out to~30,000 km s-1 using the fully corrected magnitudes andvelocities, corrected for streaming motions. Nine solutions for theintercept magnitudes in these diagrams show extreme stability at the0.02 mag level using various subsamples of the data for both low andhigh extinctions in the sample, proving the validity of the correctionsfor host galaxy absorption. We shall use the same precepts for fullycorrecting SN magnitudes for the luminosity recalibration of SNe Ia inthe forthcoming final review of our Hubble Space Telescope Cepheid-SNexperiment for the Hubble constant.
| Spectroscopic Observations and Analysis of the Unusual Type Ia SN 1999ac
We present optical spectra of the peculiar Type Ia supernova (SN Ia)1999ac. The data extend from -15 to +42 days with respect to B-bandmaximum and reveal an event that is unusual in several respects. Priorto B-band maximum, the spectra resemble those of SN 1999aa, a slowlydeclining event, but possess stronger Si II and Ca II signatures (morecharacteristic of a spectroscopically normal SN). Spectra after theB-band maximum appear more normal. The expansion velocities inferredfrom the iron lines appear to be lower than average, whereas theexpansion velocity inferred from calcium H and K are higher thanaverage. The expansion velocities inferred from Si II are among theslowest ever observed, although SN 1999ac is not particularly dim. Theanalysis of the parameters v10(Si II), R(Si II), v˙, andΔm15 further underlines the unique characteristics ofSN 1999ac. We find convincing evidence of C II λ6580 in the day-15 spectrum with ejection velocity v>16,000 km s-1, butthis signature disappears by day -9. This rapid evolution at early timeshighlights the importance of extremely early-time spectroscopy.
| Spectral homogeneity of type Ia supernovae
I present a newly defined set of spectral indicators for type Ia SNe. Iuse these indicators to characterize the evolution of these objects withphase and to study the issue of spectral homogeneity from a quantitativepoint of view. I present an example of a new spectral parameter and itscorrelation to the secondary lightcurve-shape parameter of the standardcandle, Δm15(B).
| 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
| Infrared Observations of Galaxies in the Local Universe. II. 391 Calibrated Images with Photometric and Structural Measurements
This paper presents empirical results from a deep imaging survey ofgalaxies in the local universe at the J and Ks wavelengths.Three hundred ninety-one images have been obtained and calibrated usingthe same camera and filter set with the Steward Observatory 1.6 m KuiperTelescope on Mount Bigelow and the 2.3 m Bok Telescope on Kitt Peak. Thelimiting magnitude is typically 22 mag arcsec-1 at J and 21mag arcsec-1 at Ks. The central surfacebrightness, apparent magnitudes, sizes, scale lengths, and inclinationsare tabulated from measurements made using these data. The purpose ofthis paper is to provide basic near-infrared data on a variety of galaxytypes.
| Cosmological Results from High-z Supernovae
The High-z Supernova Search Team has discovered and observed eight newsupernovae in the redshift interval z=0.3-1.2. These independentobservations, analyzed by similar but distinct methods, confirm theresults of Riess and Perlmutter and coworkers that supernova luminositydistances imply an accelerating universe. More importantly, they extendthe redshift range of consistently observed Type Ia supernovae (SNe Ia)to z~1, where the signature of cosmological effects has the oppositesign of some plausible systematic effects. Consequently, thesemeasurements not only provide another quantitative confirmation of theimportance of dark energy, but also constitute a powerful qualitativetest for the cosmological origin of cosmic acceleration. We find a ratefor SN Ia of(1.4+/-0.5)×10-4h3Mpc-3yr-1at a mean redshift of 0.5. We present distances and host extinctions for230 SN Ia. These place the following constraints on cosmologicalquantities: if the equation of state parameter of the dark energy isw=-1, then H0t0=0.96+/-0.04, andΩΛ-1.4ΩM=0.35+/-0.14. Includingthe constraint of a flat universe, we findΩM=0.28+/-0.05, independent of any large-scalestructure measurements. Adopting a prior based on the Two Degree Field(2dF) Redshift Survey constraint on ΩM and assuming aflat universe, we find that the equation of state parameter of the darkenergy lies in the range -1.48-1, we obtain w<-0.73 at 95% confidence.These constraints are similar in precision and in value to recentresults reported using the WMAP satellite, also in combination with the2dF Redshift Survey.Based in part on observations with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy (AURA), Inc.,under NASA contract NAS 5-26555. This research is primarily associatedwith proposal GO-8177, but also uses and reports results from proposalsGO-7505, 7588, 8641, and 9118.Based in part on observations taken with the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, le Centre National de la Recherche Scientifique de France, and the University of Hawaii. CTIO: Based in part on observations taken at the Cerro Tololo Inter-American Observatory.Keck: Some of the data presented herein were obtained at the W. M. KeckObservatory, which is operated as a scientific partnership among theCalifornia Institute of Technology, the University of California, and theNational Aeronautics and Space Administration. The Observatory was madepossible by the generous financial support of the W. M. Keck Foundation.UH: Based in part on observations with the University of Hawaii 2.2 mtelescope at Mauna Kea Observatory, Institute for Astronomy, University ofHawaii. UKIRT: Based in part on observations with the United KingdomInfrared Telescope (UKIRT) operated by the Joint Astronomy Centre on behalfof the UK. Particle Physics and Astronomy Research Council. VLT: Based inpart on observations obtained at the European Southern Observatory,Paranal, Chile, under programs ESO 64.O-0391 and ESO 64.O-0404. WIYN: Based in part on observations taken at the WIYN Observatory, a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories.
| Classifications of the Host Galaxies of Supernovae
Classifications on the DDO system are given for the host galaxies of 177supernovae (SNe) that have been discovered since 1997 during the courseof the Lick Observatory Supernova Search with the Katzman AutomaticImaging Telescope. Whereas SNe Ia occur in all galaxy types, it isfound, at a high level of statistical confidence, that SNe Ib, Ic, andII are strongly concentrated in late-type galaxies. However, attentionis drawn to a possible exception provided by SN 2001I. This SN IInoccurred in the E2 galaxy UGC 2836, which was not expected to harbor amassive young supernova progenitor.
| The Progenitors of Subluminous Type Ia Supernovae
We find that spectroscopically peculiar subluminous Type Ia supernovae(SNe Ia) come from an old population. Of the 16 subluminous SNe Iaknown, 10 are found in E/S0 galaxies, and the remainder are found inearly-type spiral galaxies. The probability that this is a chanceoccurrence is only 0.2%. The finding that subluminous SNe Ia areassociated with an older stellar population indicates that for asufficiently large look-back time (already accessible in currenthigh-redshift searches) they will not be found. Due to a scarcity in oldpopulations, hydrogen and helium main-sequence stars and He red giantstars that undergo Roche lobe overflow are unlikely to be theprogenitors of subluminous SNe Ia. Earlier findings that overluminousSNe Ia [Δm15(B)<~0.95] come from a young progenitorpopulation are confirmed. The fact that subluminous SNe Ia andoverluminous SNe Ia come from different progenitor populations and alsohave different properties is a prediction of the CO white dwarf mergerprogenitor scenario.
| A High Intrinsic Peculiarity Rate among Type IA Supernovae
We have compiled a sample of 45 Type Ia supernovae (SNe Ia) discoveredby the Lick Observatory Supernova Search (LOSS) and the BeijingAstronomical Observatory Supernova Survey (BAOSS), and determined therate of spectroscopically peculiar SNe Ia (i.e., SN 1986G-like, SN1991bg-like, and SN 1991T-like objects) and the luminosity function ofSNe Ia. Because of the nature of the two surveys (distance-limited withsmall baselines and deep limiting magnitudes), nearly all SNe Ia havebeen discovered in the sample galaxies of LOSS and BAOSS; thus, theobserved peculiarity rate and luminosity function of SNe Ia areintrinsic. We find that 36%+/-9% of nearby SNe Ia are peculiar;specifically, the luminosity function of SNe Ia consists of 20% SN1991T-like, 64% normal, and 16% SN 1991bg-like objects. We have comparedour results to those found by earlier studies, and to those found athigh redshift. The apparent dearth of SN 1991T-like objects at highredshift may be due to extinction, and especially to the difficulty ofrecognizing them from spectra obtained past maximum brightness or fromspectra with low signal-to-noise ratios. Implications of the highpeculiarity rate for the progenitor systems of SNe Ia are also brieflydiscussed.
| Supernova 1999by in NGC 2841
IAUC 7158 available at Central Bureau for Astronomical Telegrams.
| Supernovae 1998bu, 1999D, 1999E, 1999X, 1999Z, 1999ac, 1999ai
IAUC 7144 available at Central Bureau for Astronomical Telegrams.
| Comet C/1999 G2 (SOHO)
IAUC 7142 available at Central Bureau for Astronomical Telegrams.
| Supernova 1999ac in NGC 6063
IAUC 7122 available at Central Bureau for Astronomical Telegrams.
| Supernova 1999ac in NGC 6063
IAUC 7114 available at Central Bureau for Astronomical Telegrams.
| 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.
| Infrared Observations of Galaxies in the Local Universe. I. The Survey and Some Representative Results
This paper introduces a continuing survey of galaxies in the localuniverse. Consistent deep images are being acquired for a representativesample of 321 galaxies in the Uppsala General Catalogue down to 21.7 magarcsec-2 at Ks (2.16 mu m) and 22.4 mag arcsec-2 at J (1.25 mu m) usinga NICMOS camera with a 3.'8 x 3.'8 field of view attached to the 61 inch(1.5 m) telescope on Mount Bigelow. We provide some examples of theresults being obtained by employing 64 deep images of a subset of 44galaxies. Bulge-to-disk ratios are tabulated for 30 galaxies. Thebrightness of the central region of 44 galaxies declines approximately 5mag from Hubble type S0 to Sm. An exponential vertical scale height atKs is found to be 500 pc for the disk of UGC 5173. Arm amplitudes offour nearly face-on spiral galaxies are found to range between 11% and88% compared to the interarm region. There is some evidence that the armamplitude is larger at Ks than it is at J. Color gradients are measuredfor 15 galaxies with only one showing a significant nonzero result. Ameasurement of galactic symmetry applied to 64 deep images reveals anaverage asymmetry of 7.6% ( sigma = 4.6%) for these galaxies.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| Optical Rotation Curves and Linewidths for Tully-Fisher Applications
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2402C&db_key=AST
| Deep r-Band Photometry for Northern Spiral Galaxies
We present r-band surface photometry for 349 northern Sb-Sc UGCgalaxies, from a total of 627 CCD images. For each galaxy, we presentsurface brightness profiles, isophotal and total magnitudes, isophotalradii, and structural parameters from exponential fits to the disk. Onehundred ninety-five galaxies have been observed more than once. Allnights with a photometric transformation scatter greater than 0.022 magwere rejected. Sky errors are investigated carefully and yield profilesthat are reliable down to 26 r mag arcsec^-2^, Deep isophotal magnitudesare as accurate as +/-0.019, and extrapolated magnitudes are internallyconsistent to within 0.020. We compare visual (UGC) and CCD isophotaldiameters and show that axial ratio must be included as a thirdparameter. Comparison with the r-band CCD photometry of Kent andWillick, and accounting for sky errors, suggest typical errors for totalmagnitudes of +/-0.08. Our data are also shown to be zero-pointed on thesame Gunn r system as that of Kent and Willick. Ellipticity measurementsagree very well except for progressively face-on galaxies where spiralstructure is more conspicuous. The ellipticity internal error is lessthan 0.02, or about 3^deg^ for inclinations. Our internal extinctioncorrection implies that disks are semitransparent in their outer parts.We caution that comparison of central surface brightnesses and scalelengths is complicated by the subjective nature of their measurement;extreme care must be applied when using such quantities. We measure anapparent Freeman law of (μ_0,c_) = 20.08 +/- 0.55 r mag arcsec^-2^.This magnitude-limited sample was originally derived for studies oflarge-scale motions in the local universe. The deep CCD photometry isalso ideally suited for matching spectroscopic studies, mass modeling,galaxy structural analysis, etc.
| 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.
| Near-infrared surface photometry of spiral galaxies. I. The data.
We present K'-band surface photometry of a sample of 31 inclined Sa-Scdgalaxies, together with additional J- and H-band data for four of them.In this first paper of a series, profiles are presented, together withglobal and isophotal parameters. Our profiles are compared to similar B,R and I data collected from other sources. Three galaxies exhibitpreviously unknown small bars in their center, while in five others,such bars may also be present. Four objects present a narrow elongatedfeature in their center aligned with their major axis, which could be aninward extension of the disk. A few galaxies display very thin spiralarms. Color-color diagrams indicate that the extinction inside the fourgalaxies for which we have JHK' images is limited to A_V_<2.
| Galaxy structures in the Hercules region
216 redshifts have been obtained in a region of 981 sq deg south of theHercules supercluster. 172 of these redshifts are of galaxies withmpg less than or equal to 15.1, 110 of which had no previousvelocity measurement. 44 new redshifts are of galaxies fainter thanmpg = 15.1. With these new data we have been able to define asample in a vast region (approximately 1700 sq deg) around Herculeslimited to mpg less than or equal to 15.1 with a velocitycompleteness of 81.5%. 189 galaxies have been morphologically classifiedso that all galaxies in the sample with known velocity now also haveknown morphology. The magnitude limited sample, including 556 galaxies,is then used to identify and describe galaxy structures in the region.We find that the overdense volume is small, that its overall appearanceis that of a coral branch floating in a sea of nothing and that earlyand late type galaxies defined different structures.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
Katalógusok és elnevezések:
|
