Elinor L. Gates

The Lick AGN Monitoring Project: Broad-line Region Radii and Black Hole Masses from Reverberation Mapping of Hβ

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0: 05) Seyfert 1 galaxies with expected masses in the range � 10 6 -10 7 Mand also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to all ow for a time lag to be measured between the continuum fluctuations and the response to these fluctuation s in the broad Hemission. We present here the light curves for all the objects in this sample and the subseq uent Htime lags for the nine objects where these measurements were possible. The Hlag time is directly related to the size of the broad-line reg ion in AGNs, and by combining the Hlag time with the measured width of the Hemission line in the variable part of the spectrum, we determine the virial mass of the central sup ermassive black hole in these nine AGNs. The absolute calibration of the black hole masses is based on the normalization derived by Onken et al., which brings the masses determined by reverberation mapping into agreement with the local MBH -�? relationship for quiescent galaxies. We also examine the time lag response as a function of velocity across the Hline profile for six of the AGNs. The analysis of four leads to rather ambiguous results with relatively flat time lags as a function of velocity. However, SBS 1116+583A exhibits a symmetric time lag response around the line center reminiscent of simple models for circularly orbiting broad -line region (BLR) clouds, and Arp 151 shows an asymmetric profile that is most easily explained by a simple g ravitational infall model. Further investigation will be necessary to fully understand the constraints place d on physical models of the BLR by the velocity- resolved response in these objects. Subject headings:galaxies: active - galaxies: nuclei - galaxies: Seyfert

High-resolution measurements of the halos of four dark matter-dominated galaxies: Deviations from a universal density profile

We derive rotation curves for four nearby, low-mass spiral galaxies and use them to constrain the shapes of their dark matter density profiles. This analysis is based on high-resolution two-dimensional Hα velocity fields of NGC 4605, NGC 5949, NGC 5963, and NGC 6689 and CO velocity fields of NGC 4605 and NGC 5963. In combination with our previous study of NGC 2976, the full sample of five galaxies contains density profiles that span the range from αDM = 0 to αDM = 1.20, where αDM is the power-law index describing the central density profile. The scatter in αDM from galaxy to galaxy is 0.44, 3 times as large as in cold dark matter (CDM) simulations, and the mean density profile slope is αDM = 0.73, shallower than that predicted by the simulations. These results call into question the hypothesis that all galaxies share a universal dark matter density profile. We show that one of the galaxies in our sample, NGC 5963, has a cuspy density profile that closely resembles those seen in CDM simulations, demonstrating that while galaxies with the steep central density cusps predicted by CDM do exist, they are in the minority. In spite of these differences between observations and simulations, the relatively cuspy density profiles we find do not suggest that this problem represents a crisis for CDM. Improving the resolution of the simulations and incorporating additional physics may resolve the remaining discrepancies. We also find that four of the galaxies contain detectable radial motions in the plane of the galaxy. We investigate the hypothesis that these motions are caused by a triaxial dark matter halo and place lower limits on the ellipticity of the orbits in the plane of the disk of 0.043-0.175.

The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method

ABSTRACT We present 30 optical spectra and 49 photometric epochs sampling the first 517 days after discovery of supernova (SN) 1999em and derive its distance through the expanding photosphere method (EPM). SN 1999em is shown to be a Type II‐plateau (II‐P) event, with a photometric plateau lasting until about 100 days after explosion. We identify the dominant ions responsible for most of the absorption features seen in the optical portion of the spectrum during the plateau phase. Using the weakest unblended absorption features to estimate photospheric velocity, we find the distance to SN 1999em to be \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfon...

The Unique type Ia supernova 2000cx in NGC 524

ABSTRACT We present extensive photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2000cx in the S0 galaxy NGC 524, which reveal it to be peculiar. Photometrically, SN 2000cx is different from all known SNe Ia, and its light curves cannot be fitted well by the fitting techniques currently available. There is an apparent asymmetry in the B‐band peak, in which the premaximum brightening is relatively fast (similar to that of the normal SN 1994D), but the postmaximum decline is relatively slow (similar to that of the overluminous SN 1991T). The color evolution of SN 2000cx is also peculiar: the (B−V)0 color has a unique plateau phase and the (V−R)0 and (V−I)0 colors are very blue. Although the premaximum spectra of SN 2000cx are similar to those of SN 1991T–like objects (with weak Si ii lines), its overall spectral evolution is quite different. The Si ii lines that emerged near maximum B‐band brightness stay strong in SN 2000cx until about 3 weeks past maximum. The change in the excita...

Berkeley Supernova Ia Program - I. Observations, data reduction and spectroscopic sample of 582 low-redshift Type Ia supernovae

In this first paper in a series, we present 1298 low-redshift (z ≲ 0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 to 2008 as part of the Berkeley Supernova Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light curves with measured distance moduli, and many of the spectra have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory and have a typical wavelength range of 3300–10 400 A, roughly twice as wide as spectra from most previously published data sets. We present our observing and reduction procedures, and we describe the resulting SN Database, which will be an online, public, searchable data base containing all of our fully reduced spectra and companion photometry. In addition, we discuss our spectral classification scheme (using the SuperNova IDentification code, snid; Blondin & Tonry), utilizing our newly constructed set of snid spectral templates. These templates allow us to accurately classify our entire data set, and by doing so we are able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, our data set includes spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. The sheer size of the BSNIP data set and the consistency of our observation and reduction methods make this sample unique among all other published SN Ia data sets and complementary in many ways to the large, low-redshift SN Ia spectra presented by Matheson et al. and Blondin et al. In other BSNIP papers in this series, we use these data to examine the relationships between spectroscopic characteristics and various observables such as photometric and host-galaxy properties.

IMPROVED STANDARDIZATION OF TYPE II-P SUPERNOVAE: APPLICATION TO AN EXPANDED SAMPLE

In the epoch of precise and accurate cosmology, cross-confirmation using a variety of cosmographic methods is paramount to circumvent systematic uncertainties. Owing to progenitor histories and explosion physics differing from those of Type Ia supernovae (SNeIa), Type II-plateau supernovae (SNeII-P) are unlikely to be affected by evolution in the same way. Based on a new analysis of 17 SNeII-P, and on an improved methodology, we find that SNeII-P are good standardizable candles, almost comparable to SNeIa. We derive a tight Hubble diagram with a dispersion of 10% in distance, using the simple correlation between luminosity and photospheric velocity introduced by Hamuy and Pinto. We show that the descendent method of Nugent etal. can be further simplified and that the correction for dust extinction has low statistical impact. We find that our SN sample favors, on average, a very steep dust law with total to selective extinction RV < 2. Such an extinction law has been recently inferred for many SNeIa. Our results indicate that a distance measurement can be obtained with a single spectrum of a SNII-P during the plateau phase combined with sparse photometric measurements.

The lick AGN monitoring project: Reverberation mapping of optical hydrogen and helium recombination lines

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3 m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range ~106-107 M ☉ and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad Hβ emission, which we have previously reported. We present here the light curves for the Hα, Hγ, He II λ4686, and He I λ5876 emission lines and the time lags for the emission-line responses relative to changes in the continuum flux. Combining each emission-line time lag with the measured width of the line in the variable part of the spectrum, we determine a virial mass of the central supermassive black hole from several independent emission lines. We find that the masses are generally consistent within the uncertainties. The time-lag response as a function of velocity across the Balmer line profiles is examined for six of the AGNs. We find similar responses across all three Balmer lines for Arp 151, which shows a strongly asymmetric profile, and for SBS 1116+583A and NGC 6814, which show a symmetric response about zero velocity. For the other three AGNs, the data quality is somewhat lower and the velocity-resolved time-lag response is less clear. Finally, we compare several trends seen in the data set against the predictions from photoionization calculations as presented by Korista & Goad. We confirm several of their predictions, including an increase in responsivity and a decrease in the mean time lag as the excitation and ionization level for the species increases. Specifically, we find the time lags of the optical recombination lines to have weighted mean ratios of τ(Hα):τ(Hβ):τ(Hγ):τ(He I):τ(He II) = 1.54:1.00:0.61:0.36:0.25. Further confirmation of photoionization predictions for broad-line gas behavior will require additional monitoring programs for these AGNs while they are in different luminosity states.

The Lick AGN Monitoring Project: Velocity-delay Maps from the Maximum-entropy Method for Arp 151

We present velocity-delay maps for optical Hi, Hei, and He ii recombination lines in Arp 151, recovered by fitting a reverberation model to spectrophotometric monitoring data using the maximum-entropy method. Hi response is detected over the range 0-15 days, with the response confined within the virial envelope. The Balmer-line maps have similarmorphologies but exhibit radial stratification, with progressively longer delays for Hγ to Hβ to Hα. The He i and He ii response is confined within 1-2 days. There is a deficit of prompt response in the Balmer-line cores but strong prompt response in the red wings. Comparison with simple models identifies two classes that reproduce these features: free-falling gas and a half-illuminated disk with a hot spot at small radius on the receding lune. Symmetrically illuminated models with gas orbiting in an inclined disk or an isotropic distribution of randomly inclined circular orbits can reproduce the virial structure but not the observed asymmetry. Radial outflows are also largely ruled out by the observed asymmetry. A warped-disk geometry provides a physically plausible mechanism for the asymmetric illumination and hot spot features. Simple estimates show that a disk in the broad-line region of Arp 151 could be unstable to warping induced by radiation pressure. Our results demonstrate the potential power of detailed modeling combined with monitoring campaigns at higher cadence to characterize the gas kinematics and physical processes that give rise to the broad emission lines in active galactic nuclei.

The lick agn monitoring project 2011: Fe II reverberation from the outer broad-line region

The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including Hβ and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases, the measured lag (τcen) of Fe II is longer than that of Hβ, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Veron-Cetty et al., we find τcen (Fe II)/τcen (Hβ) = 1.9 ± 0.6 in NGC 4593 and 1.5 ± 0.3 in Mrk 1511. The detection of highly correlated variations between Fe II and continuum emission demonstrates that the Fe II emission in these galaxies originates in photoionized gas, located predominantly in the outer portion of the broad-line region.

The Type Ia supernova 1999aw: a probable 1999aa-like event in a low-luminosity host galaxy

SN 1999aw was discovered during the first campaign of the Nearby Galaxies Supernova Search project. This luminous, slow-declining [Δm15(B) = 0.81 ± 0.03] Type Ia supernova was noteworthy in at least two respects. First, it occurred in an extremely low luminosity host galaxy that was not visible in the template images nor in initial subsequent deep imaging. Second, the photometric and spectral properties of this supernova indicate that it very likely was similar to the subclass of Type Ia supernovae whose prototype is SN 1999aa. This paper presents the BVRI and JsHKs light curves of SN 1999aw (through ~100 days past maximum light), as well as several epochs of optical spectra. From these data, we calculate the bolometric light curve and give estimates of the luminosity at maximum light and the initial 56Ni mass. In addition, we present deep BVI images obtained recently with the Baade 6.5 m telescope at Las Campanas Observatory that reveal the remarkably low-luminosity host galaxy.