We use the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) to test the ubiquity of infall patterns around galaxy clusters and measure cluster mass profiles to large radii. The Cluster and Infall Region Nearby Survey (CAIRNS) found infall patterns in nine clusters, but the cluster sample was incomplete. Here we match X-ray cluster catalogs with SDSS, search for infall patterns, and compute mass profiles for a complete sample of X-ray-selected clusters. Very clean infall patterns are apparent in most of the clusters, with the fraction decreasing with increasing redshift due to shallower sampling. All 72 clusters in a well-defined sample limited by redshift (ensuring good sampling) and X-ray flux (excluding superpositions) show infall patterns sufficient to apply the caustic technique. This sample is by far the largest sample of cluster mass profiles extending to large radii to date. Similar to CAIRNS, cluster infall patterns are better defined in observations than in simulations. Further work is needed to determine the source of this difference. We use the infall patterns to compute mass profiles for 72 clusters and compare them to model profiles. Cluster scaling relations using caustic masses agree well with those using X-ray or virial mass estimates, confirming the reliability of the caustic technique. We confirm the conclusion of CAIRNS that cluster infall regions are well fitted by Navarro-Frenk-White (NFW ) and Hernquist profiles and poorly fitted by singular isothermal spheres. This much larger sample enables new comparisons of cluster properties with those in simulations. The shapes (specifically NFW concentrations) of the mass profiles agree well with the predictions of simulations. The mass in the infall region is typically comparable to or larger than that in the virial region. Specifically, the mass inside the turnaround radius is on average 2:19 AE 0:18 times that within the virial radius. This ratio agrees well with recent predictions from simulations of the final masses of dark matter halos.

The CAIRNS (Cluster And Infall Region Nearby Survey) project is a spectroscopic survey of the infall regions surrounding eight nearby, rich, X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or remeasured) within ∼ 5 − 10h −1 Mpc of the centers of the clusters, making it the largest study of the infall regions of clusters. We determine cluster membership and the mass profiles of the clusters based on the phase space distribution of the galaxies. All of the clusters display decreasing velocity dispersion profiles. The mass profiles are fit well by functional forms based on numerical simulations but exclude an isothermal sphere. Specifically, NFW and Hernquist models provide good descriptions of cluster mass profiles to their turnaround radii. Our sample shows that the predicted infall pattern is ubiquitous in rich, X-ray luminous clusters over a large mass range. The caustic mass estimates are in excellent agreement with independent X-ray estimates at small radii and with virial estimates at intermediate radii. The mean ratio of the caustic mass to the X-ray mass is 1.03 ± 0.11 and the mean ratio of the caustic mass to the virial mass (when corrected for the surface pressure term) is 0.93 ± 0.07. We further demonstrate that the caustic technique provides reasonable mass estimates even in merging clusters. the infall regions of six of the eight clusters in this survey.The CAIRNS project tests whether the caustic pattern described in DG and D99 is common in nearby rich clusters and thus evaluates the feasibility of measuring cluster mass profiles at large radii from redshift surveys using the caustic technique. Other goals of CAIRNS include (1) measuring the mass-to-light ratio as a function of scale (Rines et al. 2000(Rines et al. , 2001a, (2) detecting substructures in infall regions as a probe of structure formation (Rines et al. 2001b(Rines et al. , 2002, and (3) studying the dependence of the spectroscopic properties of galaxies on environment over a large range of densities.CAIRNS also provides an important zero-redshift benchmark for comparison with more distant systems (e.g., Ellingson et al. 2001). The CNOC1 project assembled an ensemble cluster from X-ray selected clusters at moderate redshifts. The CNOC1 ensemble cluster samples galaxies up to ∼2 virial radii (see Carlberg et al. 1997a; Ellingson et al. 2001, and references therein). The caustic pattern is easily visible in the ensemble cluster, but Carlberg et al. (1997a) apply only Jeans analysis to the cluster to determine an average mass profile. Recently, Biviano & Girardi (2003) analyzed cluster redshifts from the 2dF 100,000 redshift data release. They stacked 43 poor clusters to produce an ensemble cluster containing 1345 galaxies within 2 virial radii and analyzed the properties of the ensemble cluster with both Jeans analysis and the caustic technique. Biviano & Girardi (2003) find good agreement between the two techniques; the caustic mass profile beyond the virial radius agrees well with an extrapolation of the Jeans ...

The infall regions of galaxy clusters represent the largest gravitationally bound structures in a ΛCDM universe. Measuring cluster mass profiles into the infall regions provides an estimate of the ultimate mass of these haloes. We use the caustic technique to measure cluster mass profiles from galaxy redshifts obtained with the Hectospec Cluster Survey (HeCS), an extensive spectroscopic survey of galaxy clusters with MMT/Hectospec. We survey 58 clusters selected by X-ray flux at 0.1

We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SN Ia to date, nearly doubling the number of well-observed, nearby SN Ia with published multicolor CCD light curves. The large sample of U-band photometry is a unique addition, with important connections to SN Ia observed at high redshift. The decline rate of SN Ia U-band light curves correlates well with the decline rate in other bands, as does the U −B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to B-band.Subject headings: supernovae: general -techniques: photometric Data and Reduction DiscoveryOur program of supernova photometry consists solely of follow-up; we search only our email, not the sky, to find new supernovae. A number of observers, both amateur and professional, are engaged in searching for supernovae. We rely on these searches, as well as prompt notification of candidates, coordinated by Dan Green and Brian Marsden of the IAU's Central Bureau for Astronomical Telegrams (CBAT), with confirmed SN reported in the IAU Circulars. In some cases the SN discoverers provide spectroscopic classification of the new objects, but generally spectroscopy is obtained by others, and reported separately in the IAU Circulars. With our spectroscopic SN follow-up program at the F. L. Whipple Observatory 1.5m telescope and FAST spectrograph (Fabricant et al. 1998), we have classified a large fraction of the new, nearby supernovae reported over the last several years and compiled a large spectroscopic database (Matheson et al. 2005, in preparation).Given a newly discovered and classified supernova, several factors help determine whether or not we include it in our monitoring program. Because of their importance, SN Ia are often given higher priority over other types, but factors such as ease of observability (southern targets and those discovered far to the west are less appealing), supernova phase (objects whose spectra indicate they are after maximum light are given lower priority), redshift (more nearby objects are favored), as well as the number of objects we are already monitoring are significant. Our final sample of well-observed SN Ia is not obtained from a single well-defined set of criteria, and selection effects in both the searches and follow-up may make this sample unsuitable for some applications (such as determining the intrinsic luminosity function of SN Ia, for example). A thorough discussion of the selection biases in the Calán/Tololo supernova search and follow-up campaign can be found in Hamuy & Pinto (1999).The discovery data for the sample of SN Ia presented here are given in Table 1. All of the ...

We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN2012cg at 15 and 16 days before maximum B-band brightness. The emission is consistent with predictions for the impact of the supernova on a nondegenerate binary companion. This is the first evidence for emission from a companion to a normal SNIa. Sixteen days before maximum light, the B V -color of SN2012cg is 0.2 mag bluer than for other normal SNIa. At later times, this supernova has a typical SNIa light curve, with extinction-corrected M 19.62 0.02 B = - mag and m B 0.86 0.02 15 ( ) D =  . Our data set is extensive, with photometry in seven filters from five independent sources. Early spectra also show the effects of blue light, and high-velocity features are observed at early times. Near maximum, the spectra are normal with a silicon velocity v Si =−10,500 km s −1 . Comparing the early data with models by Kasen favors a main-sequence companion of about six solar masses. It is possible that many other SN Ia have main-sequence companions that have eluded detection because the emission from the impact is fleeting and faint.

We investigate the environmental dependence of star formation in cluster virial regions and infall regions as part of CAIRNS (Cluster And Infall Region Nearby Survey), a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. We use complete, homogeneous spectroscopic surveys of K s limited samples in eight of the CAIRNS clusters. Our long-slit spectroscopy yields estimates of star formation rates in environments from cluster cores to the general large-scale structure. Galaxies in infall regions probe whether processes affecting star formation are effective over scales larger than cluster virial regions. The fraction of galaxies with current star formation in their inner disks as traced by Hα emission increases with distance from the cluster and converges to the "field" value only at 2-3 virial radii, in agreement with other investigations. However, among galaxies with significant current star formation (EW[Hα]≥2Å), there is no difference in the distribution of EW[Hα] inside and outside the virial radius. This surprising result, first seen by Carter et al., suggests that (1) star formation is truncated on either very short timescales or only at moderate and high redshifts or (2) that projection effects contaminate the measurement. We quantify the possible impact of mechanisms which only affect the outer parts of galaxies and thus might not be detected in this survey or any fiber-based survey. The number density profiles of star-forming and non-star-forming galaxies indicate that, among galaxies projected inside the virial radius, at least half of the former and 20% of the latter are "infall interlopers," galaxies in the infall region but outside the virial region. We show that the kinematics of star-forming galaxies in the infall region closely match those of absorption-dominated galaxies. This result shows that the star forming galaxies in the infall regions are not interlopers from the field and excludes one model of the backsplash scenario of galaxy transformation. Finally, we quantify systematic uncertainties in estimating the global star formation in galaxies from their inner disks.

We present 432 low-dispersion optical spectra of 32 Type Ia supernovae (SNe Ia) that also have well-calibrated light curves. The coverage ranges from 6 epochs to 36 epochs of spectroscopy. Most of the data were obtained with the 1.5 m Tillinghast telescope at the F. L. Whipple Observatory with typical wavelength coverage of 3700-7400 Å and a resolution of ∼7 Å. The earliest spectra are 13 days before B-band maximum; two-thirds of the SNe were observed before maximum brightness. Coverage for some SNe continues almost to the nebular phase. The consistency of the method of observation and the technique of reduction makes this an ideal data set for studying the spectroscopic diversity of SNe Ia.

We report a new determination of the faint end of the galaxy luminosity function (LF) in the nearby clusters Abell 2199 and Virgo using data from the Sloan Digital Sky Survey (SDSS) and the Hectospec multifiber spectrograph on the MMT. The luminosity function of A2199 is consistent with a single Schechter function to M r = −15.6 + 5 log h 70 with a faint-end slope of α = −1.13 ± 0.07 (statistical). The LF in Virgo extends to M r ≈ −13.5 ≈ M * + 8 and has a slope of α = −1.28 ± 0.06 (statistical). The red sequence of cluster members is prominent in both clusters, and almost no cluster galaxies are redder than this sequence. A large fraction of photometric red-sequence galaxies lies behind the cluster. We compare our results to previous estimates and find poor agreement with estimates based on statistical background subtraction but good agreement with estimates based on photometric membership classifications (e.g., colors, morphology, surface brightness). We conclude that spectroscopic data are critical for estimating the faint end of the LF in clusters. The faint-end slope we find is consistent with values found for field galaxies, weakening any argument for environmental evolution in the relative abundance of dwarf galaxies. However, dwarf galaxies in clusters are significantly redder than field galaxies of similar luminosity or mass, indicating that star-formation processes in dwarfs do depend on environment.