BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa

Space telescope and optical reverberation mapping project. IV. Anomalous behavior of the broad ultraviolet emission lines in NGC 5548

During an intensive Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) UV monitoring campaign of the Seyfert 1 galaxy NGC 5548 performed from 2014 February to July, the normally highly correlated far UV continuum and broad emission line variations decorrelated for ∼60-70 days, starting ∼75 days after the first HST/COS observation. Following this anomalous state, the flux and variability of the broad emission lines returned to a more normal state. This transient behavior, characterized by significant deficits in flux and equivalent width of the strong broad UV emission lines, is the first of its kind to be unambiguously identified in an active galactic nucleus reverberation mapping campaign. The largest corresponding emission line flux deficits occurred for the high ionization, collisionally excited lines C iv and Si iv(+O iv]), and also He ii(+O iii]), while the anomaly in Lywas substantially smaller. This pattern of behavior indicates a depletion in the flux of photons with Eph > 54 eV relative to those near 13.6 eV. We suggest two plausible mechanisms for the observed behavior: (i) temporary obscuration of the ionizing continuum incident upon broad line region (BLR) clouds by a moving veil of material lying between the inner accretion disk and inner (BLR), perhaps resulting from an episodic ejection of material from the disk, or (ii) a temporary change in the intrinsic ionizing continuum spectral energy distribution resulting in a deficit of ionizing photons with energies >54 eV, possibly due to a transient restructuring of the Comptonizing atmosphere above the disk. Current evidence appears to favor the latter explanation.Publisher PDFPeer reviewe

Space telescope and optical reverberation mapping project. VII. Understanding the ultraviolet anomaly in NGC 5548 with X-Ray spectroscopy

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on-and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.National Aeronautics and Space Administration (NASA) through Chandra by the Chandra X-ray Observatory Center G04-15114X NASA NAS8-03060 NAS 5-26555 NASA through a grant from the Space Telescope Science Institute GO-13330 NSF AST-1515876 AST-1515927 AST-1211916 STFC ST/M001296/1 UK Space Agency TABASGO Foundation Christopher R. Redlich Fund CONACYT 168519 PAIIPIT IN10421

Active galactic nuclei at z ∼ 1.5 – II. Black hole mass estimation by means of broad emission lines

This is the second in a series of papers aiming to test how the mass (M-BH), accretion rate (M) over dot and spin (a(*)) of supermassive black holes (SMBHs) determine the observed properties of type I active galactic nuclei (AGN). Our project utilizes a sample of 39 unobscured AGN at z similar or equal to 1.55 observed by Very Large Telescope/X-Shooter, selected to map a large range in M-BH and L/L-Edd and covers the most prominent UV-optical (broad) emission lines, including H alpha, H beta, Mg II lambda 2798 and C IV lambda 1549. This paper focuses on single-epoch, 'virial' M-BH determinations from broad emission lines and examines the implications of different continuum modelling approaches in line width measurements. We find that using a local power-law continuum instead of a physically motivated thin disc continuum leads to only slight underestimation of the full width at half-maximum (FWHM) of the lines and the associated M-BH(FWHM). However, the line dispersion sigma(line) and associated M-BH(sigma(line)) are strongly affected by the continuum placement and provides less reliable mass estimates than FWHM-based methods. Our analysis shows that H alpha, H beta and M II can be safely used for virial M-BH estimation. The CIV line, on the other hand, is not reliable in the majority of the cases; this may indicate that the gas emitting this line is not virialized. While H alpha and H beta show very similar line widths, the mean FWHM(MgII) is about 30 per cent narrower than FWHM(H beta). We confirm several recent suggestions to improve the accuracy in C IV-based mass estimates, relying on other UV emission lines. Such improvements do not reduce the scatter between C IV-based and Balmer-line-based mass estimatesCONICYT-PCHA/doctorado Nacional para extranjeros 2013-63130316 Fondecyt 1120328 Israel Science Foundation 284/1

The virial factor and biases in single epoch black hole mass determinations

Accurately determining the masses of supermassive black holes is crucial to understand their evolution and the establishment of their relationship with their host galaxy properties. Beyond the local universe, the single epoch mass estimation method provides a simple procedure to estimate black hole masses in large spectroscopic samples of type-1 active galactic nuclei. The method assumes virialized motion of gas in the close vicinity to the active black holes, traced through broad emission lines. However, because of the assumption of a universal virial factor, this procedure has uncertainties associated with the unknown distribution of the gas clouds. Here, using a sample of 39 quasars observed with the VLT/X-shooter spectrograph, we compare alternative estimations of black hole masses determined from the properties of the accretion disk emission around the black hole with the single epoch virial mass estimations. We find that the virial factor is inversely proportional to the observed width of the broad emission lines. This result implies that current virial masses can be miss-estimated by up to a factor of 6. Our analysis indicates that either the effect of line-of-sight inclination in a planar distribution of the broad line emitting gas or the radiation pressure perturbations to the distribution of gas can reproduce our findings.CONICYT-PCHA/doctorado Nacional para extranjeros 2013-63130316 Fondecyt Project 1161184 Israel Science Foundation 234/1

Long-term monitoring of the archetype Seyfert galaxy MCG-6-30-15: X-ray, optical and near-IR variability of the corona, disc and torus

Artículo de publicación ISIWe present long-term monitoring of MCG-6-30-15 in X-rays, optical and near-IR wavelengths, collected over 5 yr of monitoring. We determine the power spectrum density of all the observed bands and show that after taking into account the host contamination similar power is observed in the optical and near-IR bands. There is evidence for a correlation between the light curves of the X-ray photon flux and the optical B band, but it is not possible to determine a lag with certainty, with the most likely value being around 0 d. Strong correlation is seen between the optical and near-IR bands. Cross-correlation analysis shows some complex probability distributions and lags that range from 10 to 20 d, with the near-IR following the optical variations. Filtering the light curves in frequency space shows that the strongest correlations are those corresponding to the shortest time-scales. We discuss the nature of the X-ray variability and conclude that this is intrinsic and cannot be accounted for by absorption episodes due to material intervening in the line of sight. It is also found that the lags agree with the relation τ ∝ λ4/3, as expected for an optically thick geometrically thin accretion disc, although for a larger disc than that predicted by the estimated black hole mass and accretion rate in MCG-6- 30-15. The cross-correlation analysis suggests that the torus is located at ∼20 light-days from the central source and at most at ∼50 light-days from the central region. This implies an active galactic nucleus bolometric luminosity of ∼3 × 1043 erg s−1 cm−2

Introducing the search for intermediate-mass black holes in Nearby Galaxies (SIBLING) Survey

Intermediate-mass black holes (IMBHs) have masses between 10(2) and 10(6) M<sub and are key to our understanding of the formation of massive black holes. The known population of IMBHs remains small, with a few hundred candidates and only a handful of them confirmed as bona fide IMBHs. Until now, the most widely used selection method is based on spectral analysis. Here we present a methodology to select IMBH candidates via optical variability analysis of the nuclear region of local galaxies (z <= 0.35). Active IMBHs accreting at low rates show small amplitude variability with timescales of hours, as is seen in one of the known IMBHs, NGC 4395. We found a sample of similar to 500 galaxies demonstrating fast and small amplitude variation in their week-based light curves. We estimate an average occupancy fraction of 4% and a surface density of similar to 3 deg(-2), which represent an increase by a factor of similar to 40 compared to previous searches. A large fraction (78%) of the candidates are in spiral galaxies. We preliminarily confirm the active galactic nucleus nature of 22 sources via Baldwin, Phillips, and Terlevich diagrams using Sloan Digital Sky Survey legacy spectra. Further confirmation of these candidates will require multiwavelength observations, especially in X-ray and radio bands.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) PCHA/Doctorado-Nacional/2014-21140892 Ministry of Economy, Development, and Tourism's Millennium Science Initiative IC120009 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1161184 11130228 Center of Excellence in Astrophysics and Associated Technologies PFB 06 Basal Project, Centro de Modelamiento Matemaico, Universidad de Chile PFB-03 High Performance Computing infrastructure of the National Laboratory for High Performance Computing (NLHPC), CONICYT PIA ECM-02 United States Department of Energy (DOE) National Science Foundation (NSF) Spanish Government Science & Technology Facilities Council (STFC) Higher Education Funding Council for England National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign Ohio State University Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University Ciencia Tecnologia e Inovacao (FINEP) Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro National Council for Scientific and Technological Development (CNPq) German Research Foundation (DFG) United States Department of Energy (DOE) University of Chicago University of California at Santa Cruz University of Cambridge Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid University of Chicago University College London DESBrazil Consortium University of Edinburgh ETH Zurich United States Department of Energy (DOE) University of Chicago University of Illinois at UrbanaChampaign Institut de Ciencies de l'Espai (IEEC/CSIC) Institut de Fisica d'Altes Energies United States Department of Energy (DOE) Ludwig-Maximilians Universitat Munchen associated Excellence Cluster Universe University of Michigan System National Science Foundation (NSF) NSF - Directorate for Mathematical & Physical Sciences (MPS) University of Nottingham Ohio State University OzDES Membership Consortium University of Pennsylvania University of Portsmouth SLAC National Accelerator Laboratory Stanford University University of Sussex Texas AM University Kavli Institute of Cosmological Physics at the University of Chicago Ministerio da Ciencia, Tecnologia e Inovaca

The effect of nuclear gas distribution on the mass determination of supermassive black holes

Supermassive black holes reside in the nuclei of most galaxies. During their active episodes, black holes are powered by accretion discs where gravitational energy is converted into radiation(1). Accurately determining black hole masses is key to understand how the population evolves over time and how the black holes relate to their host galaxies(2-4). Beyond the local universe, z greater than or similar to 0.2, the mass is commonly estimated assuming a virialized motion of gas in the close vicinity of the active black holes, traced through broad emission lines(5,6). However, this procedure has uncertainties associated with the unknown distribution of the gas clouds. Here, we show that the black hole masses derived from the properties of the accretion disk and virial mass estimates differ by a factor that is inversely proportional to the width of the broad emission lines. This leads to virial mass misestimations up to a factor of six. Our results suggest that a planar gas distribution that is inclined with respect to the line of sight may account for this effect. However, radiation pressure effects on the distribution of gas can also reproduce our results. Regardless of the physical origin, our findings contribute to mitigating the uncertainties in current black hole mass estimations and, in turn, will help us to better understand the evolution of distant supermassive black holes and their host galaxies.CONICYT-PCHA/doctorado Nacional para extranjeros 2013-63130316 Fondecyt 1161184 Israel Science Foundation 234/1