Kenneth Rines

CfA3: 185 Type Ia Supernova Light Curves from the CfA

We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains the largest number of homogeneously observed and reduced nearby SNe Ia (z 0.08) published to date. It more than doubles the nearby sample, bringing SN Ia cosmology to the point where systematic uncertainties dominate. Our natural system photometry has a precision of 0.02 mag in BVRIri and 0.04 mag in U for points brighter than 17.5 mag. We also estimate a systematic uncertainty of 0.03 mag in our SN Ia standard system BVRIri photometry and 0.07 mag for U. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars, where available for the same SN, reveal agreement at the level of a few hundredths mag in most cases. We find that 1991bg-like SNe Ia are sufficiently distinct from other SNe Ia in their color and light-curve-shape/luminosity relation that they should be treated separately in light-curve/distance fitter training samples. The CfA3 sample will contribute to the development of better light-curve/distance fitters, particularly in the few dozen cases where near-infrared photometry has been obtained and, together, can help disentangle host-galaxy reddening from intrinsic supernova color, reducing the systematic uncertainty in SN Ia distances due to dust.

Ubvri light curves of 44 type ia supernovae

We present UBVRI photometry of 44 Type Ia supernovae (SNe 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 SNe Ia to date, nearly doubling the number of well-observed, nearby SNe Ia with published multicolor CCD light curves. The large sample of U-band photometry is a unique addition, with important connections to SNe 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 the B band.

CAIRNS: The Cluster and Infall Region Nearby Survey. I. Redshifts and Mass Profiles

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 have collected 15,654 redshifts (3471 new or remeasured) within ~5?10 h-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 fitted 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.

CIRS: Cluster Infall Regions in the Sloan Digital Sky Survey. I. Infall Patterns and Mass Profiles

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 ± 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 Type Ia Supernova 1998bu in M96 and the Hubble Constant

We present optical and near-infrared photometry and spectroscopy of the Type Ia SN 1998bu in the Leo I Group galaxy M96 (NGC 3368). The data set consists of 356 photometric measurements and 29 spectra of SN 1998bu between UT 1998 May 11 and July 15. The well-sampled light curve indicates the supernova reached maximum light in B on UT 1998 May 19.3 (JD 2450952.8 ± 0.8) with B = 12.22 ± 0.03 and V = 11.88 ± 0.02. Application of a revised version of the Multicolor Light Curve Shape (MLCS) method yields an extinction toward the supernova of AV = 0.94 ± 0.15 mag, and indicates the supernova was of average luminosity compared to other normal Type Ia supernovae. Using the HST Cepheid distance modulus to M96 and the MLCS fitted parameters for the supernova, we derive an extinction-corrected absolute magnitude for SN 1998bu at maximum, MV = -19.42 ± 0.22. Our independent results for this supernova are consistent with those of Suntzeff et al. Combining SN 1998bu with three other well-observed local calibrators and 42 supernovae in the Hubble flow yields a Hubble constant, H0 = 64 -->img1.gif km s-1 Mpc-1, where the error estimate incorporates possible sources of systematic uncertainty including the calibration of the Cepheid period-luminosity relation, the metallicity dependence of the Cepheid distance scale, and the distance to the LMC.

CLASH: Precise new constraints on the mass profile of the galaxy cluster A2261

We precisely constrain the inner mass profile of A2261 (z = 0.225) for the first time and determine that this cluster nis not “overconcentrated” as found previously, implying a formation time in agreement with ΛCDM expectations. nThese results are based on multiple strong-lensing analyses of new 16-band Hubble Space Telescope imaging nobtained as part of the Cluster Lensing and Supernova survey with Hubble. Combining this with revised weaklensing nanalyses of Subaru wide-field imaging with five-band Subaru + KPNO photometry, we place tight new nconstraints on the halo virial mass Mvir = (2.2 ± 0.2) × 1015 M h−1 n70 (within rvir ≈ 3 Mpc h−1 n70 ) and concentration ncvir = 6.2 ± 0.3 when assuming a spherical halo. This agrees broadly with average c(M, z) predictions from recent nΛCDM simulations, which span 58. Our most significant systematic uncertainty is halo elongation nalong the line of sight (LOS). To estimate this, we also derive a mass profile based on archival Chandra X-ray nobservations and find it to be ∼35% lower than our lensing-derived profile at r2500 ∼ 600 kpc. Agreement can nbe achieved by a halo elongated with a ∼2:1 axis ratio along our LOS. For this elongated halo model, we find nMvir = (1.7 ± 0.2) × 1015 M h−1 n70 and cvir = 4.6 ± 0.2, placing rough lower limits on these values. The need nfor halo elongation can be partially obviated by non-thermal pressure support and, perhaps entirely, by systematic nerrors in the X-ray mass measurements. We estimate the effect of background structures based on MMT/Hectospec nspectroscopic redshifts and find that these tend to lower Mvir further by ∼7% and increase cvir by ∼5%. nKe

Optical spectroscopy of type Ia supernovae

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 A and a resolution of ~7 A. 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.

CAIRNS: The Cluster and Infall Region Nearby Survey. III. Environmental Dependence of Hα Properties of Galaxies

We investigate the environmental dependence of star formation in cluster virial regions and infall regions as part of the Cluster and Infall Region Nearby Survey (CAIRNS), a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. We use complete, homogeneous spectroscopic surveys of Ks-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] ≥ 2 A), there is no difference in the distribution of EW[Hα] inside and outside the virial radius. This surprising result, first seen by Carter and coworkers, suggests that (1) star formation is truncated either on 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 that 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 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.

CAIRNS: The Cluster and Infall Region Nearby Survey. II. Environmental Dependence of Infrared Mass-to-Light Ratios

CAIRNS (Cluster and Infall Region Nearby Survey) is a spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. In our previous paper, we used redshifts within ~10 h-1 Mpc of the centers of the clusters to determine the mass profiles of the clusters based on the phase-space distribution of the galaxies. Here, we use Two Micron All Sky Survey photometry and an additional 515 redshifts to investigate the environmental dependence of near-infrared mass-to-light ratios. In the virial regions, the halo occupation function is nonlinear; the number of bright galaxies per halo increases more slowly than the mass of the halo. On larger scales, the light contained in galaxies is less clustered than the mass in rich clusters. Specifically, the mass-to-light ratio inside the virial radius is a factor of 1.8 ± 0.3 larger than that outside the virial radius. This difference could result from changing fractions of baryonic to total matter or from variations in the efficiency of galaxy formation or disruption with environment. The average mass-to-light ratio M/LK = 53 ± 5 h implies Ωm = 0.18 ± 0.03 (statistical) using the luminosity density based on Two Degree Field Galaxy Redshift Survey data. These results are difficult to reconcile with independent methods that suggest higher Ωm. Reconciling these values by invoking bias requires that the typical value of M/LK changes significantly at densities of 3ρc.

Spectroscopic Determination of the Luminosity Function in the Galaxy Clusters A2199 and Virgo

We report a new determination of the faint end of the galaxy luminosity function in the nearby clusters Virgo and Abell 2199 using data from 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 alpha=-1.13+/-0.07. The LF in Virgo extends to M_r=-13.5= M^*+8 and has a slope of alpha=-1.28+/-0.06. The red sequence of cluster members is prominent in both clusters, and almost no cluster galaxies are redder than this sequence. We show that selecting objects on the red sequence and blueward produces a steeply rising faint-end. A large fraction of photometric red-sequence galaxies lie 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 luminosity function 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.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 Mr = ?15.6 + 5 log h 70 with a faint-end slope of ? = ?1.13 ? 0.07 (statistical). The LF in Virgo extends to Mr ?13.5 M* + 8 and has a slope of ? = ?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.