Home     Getting Started     To Survive in the Universe    
Inhabited Sky
    News@Sky     Astro Photo     The Collection     Forum     Blog New!     FAQ     Press     Login  

NGC 4675



Upload your image

DSS Images   Other Images

Related articles

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.

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.

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.

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.

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.

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.

Look-alike galaxies:. HI observations for look-alike galaxies of four calibrators
We present a programme aiming at applying the Tully-Fisher relation forgalaxies with the same morphological type and the same inclination(look-alike galaxies or sosie galaxies) as calibrating galaxies. Theadvantage of sosie galaxies is discussed. In particular, it is shownthat using sosies of bright calibrators will allow us to explore theuniverse deeper and more efficiently than the classical TF methodapplied to different morphological types and different inclinations. Asa preliminary part, we report in this paper new HI observationsperformed with the radiotelescope of Nançay (France) for sosiesof four calibrators NGC 224, NGC 3031, NGC 253 and NGC 5457. 82 galaxieswere detected. These observations made use of Nançayradiotelescope. The Nançay Radio Observatory is the Unitéscientifique de Nançay of the Observatoire de Paris,associated asUnité de Service et de Recherche (USR) No. B704 to the FrenchCentre National de la Recherche Scientifique (CNRS). The NançayObservatory also acknowledges the financial support of the ConseilRégional of the Région Centre in France.

Supernovae discovered in the period of July 1996-June 1997 at the BAO.
Not Available

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.

Supernova 1997Y in NGC 4675
IAUC 6557 available at Central Bureau for Astronomical Telegrams.

Supernova 1997Y in NGC 4675
IAUC 6556 available at Central Bureau for Astronomical Telegrams.

Optical Spectra of Recent Supernovae of Type Ia: SN1995AL, SN1997Y, =
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2054A&db_key=AST

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.

General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.

Hydroxyl in galaxies. I - Surveys with the NRAO 300 FT telescope
Results are presented of a search for 1667- and 1665-MHz mainline OHtransitions for 321 galaxies, which were observed during four separatesessions at the NRAO 300-ft telescope in the period 1984-1987. Threedetections of OH megamasers are reported, as well as detections of threenew OH absorption sources. The observational sample contains sourcesfrom a variety of catalogs and represents different criteria. Theresults for the whole sample confirm that FIR luminosity and colorcriteria used for these surveys are indeed optimized for findingmegamasers. The results also confirm that detecting distant highluminosity OH megamasers is considerably more successful than findingnearby weak masers.

Galaxy alignments
Large areas of the sky around the brightest apparent magnitude galaxieshave been examined. In almost every case where they are not crowded byother right galaxies, clearly marked lines of higher red shift galaxieshave been going through, or originating from, the positions of thesebright apparent magnitude galaxies. It is shown that galaxies of about3000 to 5000 km/s red shift define narrow filaments of from 10 to 50 degin length. It is found that galaxies of very bright apparent magnitudetend to occur at the center or ends of these alignments. The 20brightest galaxies in apparent magnitude north of delta = 0 deg areinvestigated here. Of the 14 which are uncrowded by nearby brightgalaxies, a total of 13 have well marked-lines and concentrations offainter, higher red shift galaxies.

Submit a new article

Related links

  • - No Links Found -
Submit a new link

Member of following groups:

Observation and Astrometry data

Constellation:Ursa Major
Right ascension:12h45m31.80s
Aparent dimensions:1.349′ × 0.427′

Catalogs and designations:
Proper Names   (Edit)
NGC 2000.0NGC 4675

→ Request more catalogs and designations from VizieR