bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inflow of atomic gas fuelling star formation
Authors: Michałowski M. J. , Gentile G. , Hjorth J. , Krumholz M. R. , Tanvir N. R. , Kamphuis P. , Burlon D. , Baes M. , Basa S. , Berta S. , Cerón J. M. Castro , Crosby D. , D'Elia V. , Elliott J. , Greiner J. , Hunt L. K. , Klose S. , Koprowski M. P. , Le Floc'h E. , Malesani D. , Murphy T. , Guelbenzu A. Nicuesa , Palazzi E. , Rasmussen J. , Rossi A. , Savaglio S. , Schady P. , de Ugarte Postigo A. , Watson D. , van der Werf P. , Vergani S. D. , Xu D. 
Published: October 2016

AbstractGamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion.
Stellar Explosions in High-surface Density Galaxies
Authors: Scannapieco Evan , Sur Sharanya , Ostriker Eve C. 
Published: October 2016

AbstractHigh surface density, rapidly star-forming galaxies are observed to have ≈ 50 - 100 km s−1 line-of-sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae.We find that such motions lead to strong global outflows in the highly-compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent today. Substantial outflows are generated if the one-dimensional horizontal velocity dispersion exceeds -35 km s−1, as occurs in the dense disks that have star formation rate densities above ≈ 0.1 M⊙ yr−1 kpc−2. These outflows are triggered by a thermal runaway, arising from the inefficient cooling of hot material coupled with successive heating from turbulent driving. Thus, even in the absence of stellar feedback, a critical value of the star-formation rate density for outflow generation can arise due to a turbulent heating instability. This suggests that in strongly self-gravitating disks, outflows may be enhanced by, but need not caused by, energy input from stellar explosions.These results are explained in more detailed in Sur, Scannapieco, & Ostriker (2015).
Type Ia Supernovae Strongly Interacting with Their Circumstellar Medium
Authors: Silverman Jeffrey M. , Nugent Peter , Gal-Yam Avishay , Howell D. A. , Sullivan Mark , Filippenko Alex 
Published: October 2016

AbstractA rare subclass of Type Ia supernovae (SNe Ia) shows evidence of strong interaction with a hydrogen-rich circumstellar medium (CSM); these objects are referred to as SNe Ia-CSM. PTF11kx began life as a SN Ia, but after a month it began to show indications of significant interaction with its CSM. This well-studied object solidified the connection between SNe Ia-CSM and more typical SNe Ia, despite their spectral similarity to Type IIn SNe (which likely come from massive star progenitors, as opposed to the white dwarf progenitors for the SNe Ia-CSM). The spectra of all ~20 known SNe Ia-CSM are dominated by Hα emission (with widths of ~2000 km s−1) and exhibit large Hα/Hβ intensity ratios; moreover, they have an almost complete lack of He I emission (see left panel of Figure 1). They also show possible evidence of dust formation through a decrease in the red wing of Hα 75–100 days past maximum brightness. The absolute magnitudes of SNe Ia-CSM are found to be -21.3 mag ≤ MR ≤ −19 mag (see right panel of Figure 1), and they also show ultraviolet emission at early times and strong infrared emission at late times (but no detected radio or X-ray emission). Finally, the host galaxies of SNe Ia-CSM imply that these objects come from a relatively young stellar population.
Extinction curves of GRB environment with the X-shooter
Authors: Gomboc Andreja , Japelj Jure , Covino Stefano 
Published: October 2016

AbstractGamma Ray Bursts (GRBs) can be used as a powerful tool to study galactic environments at different epochs of the Universe's evolution, thanks to their bright afterglow emission ranging from X-rays to optical and radio wavebands. Important aspect of the environment is dust, which plays a central role in the astrophysical processes of interstellar medium and in the formation of stars. GRBs can be a unique probe of dust at cosmological distances, where its origin and properties are still poorly known. By using a sample of GRB afterglow spectra observed with the VLT/X-shooter spectrograph we studied the rest-frame extinction in GRB lines-of-sight by modelling the broadband near-infrared to X-ray afterglow spectral energy distributions. We present our results on the rest-frame extinction of our sample, and illustrate that the spectroscopic data, thanks to a combination of excellent resolution and coverage of the blue part of the spectral energy distributions, are more successful than photometric measurements in constraining the extinction curves and therefore the dust properties in GRB hosts.
Stripped-envelope supernova rates and host-galaxy properties
Authors: Graur Or , Bianco F. B. , Modjaz M. , Maoz D. , Shivvers I. , Filippenko A. V. , Li W. 
Published: October 2016

AbstractThe progenitors of stripped-envelope supernovae (SNe Ibc) remain to be conclsuively identified, but correlations between SN rates and host-galaxy properties can constrain progenitor models. Here, we present one result from a re-analysis of the rates from the Lick Observatory Supernova Search. Galaxies with stellar masses ≲1010 M⊙ are less efficient at producing SNe Ibc than more massive galaxies. Any progenitor scenario must seek to explain this new observation.
Hunting for the faintest hosts of the brightest supernovae
Authors: Angus Charlotte R. , Levan Andrew J. , Perley Daniel A. 
Published: October 2016

AbstractSuperluminous supernovae (SLSNe) are an emerging class of SNe that exhibit luminosities exceeding those of SN Ia by an order of magnitude and have light curves with characteristic timescales of hundreds of days. Here we present observations of the host galaxies of 21 SLSNe observed with the Hubble Space Telescope, and show that their ultraviolet (UV) and near-infrared (nIR) luminosities and sizes and very different from those of the hosts of other core collapse events, with significant implications for their progenitors.
Exploring the Environment of the most powerful Explosions
Authors: Cucchiara Antonino , Rafelski Mark , Fumagalli Michele , Kocevski Daniel , Prochaska Jason X. , Cooke Ryan J. , Becker G. D. 
Published: October 2016

AbstractMore than 60 GRBs at z ≳ 1.5 reside in the vicinity of dense, cold gas as probed by the measured neutral hydrogen via afterglow absorption spectroscopy. We present the largest sample of GRB-DLAs to date in comparison with a sample of DLAs along quasars: the metallicity of the GRB hosts represents a unique tool to understand if this particular subset of galaxies can be the key ingredient for GRB formation (and massive stars) at any redshift as well as the overall cosmic star-formation rate. We show that GRB-DLAs live in a metal enriched environment, especially at z ≳ 4, likely the result of recent intense star formation and/or SNe episodes. We also derive that our metallicity measurements are broadly consistent with a mild metallicity bias for the GRB formation.
Emission-Line Diagnostics for Galaxies
Authors: Kewley Lisa J. 
Published: October 2016

AbstractI will give an overview of the emission-line diagnostics used for star-forming galaxies. I will review the UV, optical, and IR diagnostics that can be used to yield information about the ISM conditions, star-formation properties, and power sources in GRB hosts, both globally, and with spatially-resolved data. I will discuss wide integral field spectroscopy and AO-led integral field spectroscopy on current and future telescopes, focusing on the insights to be gained on the properties of GRB sites.
Gamma-ray bursts from dusty regions with little molecular gas
Authors: Hatsukade Bunyo , Ohta Kouji , Endo Akira , Nakanishi Kouichiro , Tamura Yoichi , Hashimoto Tetsuya , Kohno Kotaro 
Published: October 2016

AbstractWe detected CO line and 1.2-mm continuum emission from the two GRB host galaxies (GRB 020819B and GRB 051022) by using the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first case for detecting molecular gas emission in GRB hosts. The ratio of molecular gas to dust mass of the GRB 020819B site is significantly lower than those of the Milky Way and nearby star-forming galaxies, suggesting that the star-forming environment where the GRB occur is different from those in local galaxies. The possible reason is that much of the dense gas is dissipated by a strong interstellar ultraviolet radiation field.
Local environments of SNe Ic and Ic-BL
Authors: Selsing Jonatan , Christensen Lise , Thöne Christina , Modjaz Maryam 
Published: October 2016

AbstractWe have observed the local explosion environments of a sample Type Ic and Type Ic-BL Supernove (SNe) selected from both targeted and non-targeted surveys using VLT/VIMOS in IFU-mode. It is believed that by probing the local surroundings of the parent stellar populations of these types of SNe, valuable information can be gained about the physical conditions, which affect the type of SNe produced. The different kinds of SNe produced are determined by the initial mass and metallicity of the stellar progenitor, as well as by the metallicity-dependent mass loss in the stellar winds at the end phase of their evolution and the interaction with a sufficiently close companion star.
Effects of the Central Density Profile and the Stellar Mass Function of Merging Galaxies on Eccentricities and Coalescence Times of Supermassive Black Hole Binaries
Authors: Khan Fazeel Mahmood , Berczik Peter , Just Andreas 
Published: October 2016

AbstractIf able to coalesce in a Hubble time, Supermassive Black hole (SMBH) binaries are very promising sources of gravitational waves (GW). Our earlier studies have shown that SMBH binaries coalesce in post-merger galactic nuclei having triaxial or axisymmetric geometry in a few billion years. In this study, we model the complete evolution of SMBH binaries formed as a result of galaxy mergers having central density profiles that vary from shallow to very steep including a stellar mass function. Energy and angular momentum loss due to GW emission is taken into account using the post-Newtonian approximation. We carry out ten such simulations for each central density profile. The eccentricity of the SMBH binaries remain very high in shallow cusps and decrease systematically for steeper cusps. The coalescence times range from 0.6 to 1.5 Gyr with shorter times for steeper profiles. Typical coalescence times less than a Gyr strengthen our expectation that SMBH binaries should be very promising sources of GW radiation over a wide redshift range.
Search for Ultralight Scalar Dark Matter from Pulsar Timing
Authors: Postnov Konstantin , Porayko Nataliya 
Published: October 2016

AbstractWe perform a Bayesian analysis of pulsar-timing residuals from the NANOGrav pulsar-timing array to search for a specific form of stochastic narrow-band signal produced by oscillating gravitational potential (Gravitational Potential Background) in the Galactic halo. Such oscillations arise in models of warm dark matter composed of an ultralight massive scalar field (m ≃ 10−23 eV). The propagation of an electromagnetic signal from a pulsar through the time-dependent spacetime will leave an imprint in the pulsar timing, much like a gravitational wave. From the physical point of view, this is the classical Sachs-Wolfe effect. A distinctive feature of the pulsar-timing residuals due to GBP produced by a variable scalar field is that the amplitude of the TOA residuals should be independent of the pulsar location in the sky. In the monochromatic approximation, the stringent upper limit (95% C.L.) on the variable gravitational potential amplitude is found to be (Ψc<1.14 × 10−15), corresponding to the characteristic strain hc = 2$\sqrt{3}$Ψc < 4 × 10−15 at f=1.75 × 10−8 Hz. In the narrow-band approximation, the upper limit of this background energy density is ΩGPB < 1.27 × 10−9 at f=1.75 × 10−8 Hz. These limits are an order of magnitude higher than the expected signal amplitude assuming all Galactic dark matter is made of such scalar particles. The applied analysis of the pulsar-timing residuals can be used to search for any narrow-band stochastic signals with different correlation properties. As a by-product, parameters of the red noise present in four NANOGrav pulsars were found.
Precision Pulsar Timing with NASA's Deep Space Network
Authors: Teitelbaum Lawrence , Majid Walid , Franco Manuel M. , Hoppe Daniel J. , Horiuchi Shinji , Lazio T. Joseph W. 
Published: October 2016

AbstractMillisecond pulsars (MSPs) are a class of radio pulsars with extremely stable rotation. Their excellent timing stability can be used to study a wide variety of astrophysical phenomena. In particular, a large sample of these pulsars can be used to detect low-frequency gravitational waves. We have developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs. The DSN operates clusters of large dish antennas (up to 70-m in diameter), located roughly equidistant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations over the next few years.
The maximum spin of Millisecond Pulsar and the gravitational wave
Authors: Zhang C. M. 
Published: October 2016

AbstractThe gravitational wave radiation will release the energy momentum, which will dissipate the rotation of neutron star while in the accretion process. If the deformation of star is known, then we can estimate the maximum spin frequency of pulsar, based on which we can interpret why the spin periods of all millisecond pulsars cannot be less than one millisecond.
Origins of water in the Solar System leading to habitable worlds
Authors: Meech Karen 
Published: October 2016

AbstractLife on Earth depends on an aqueous biochemistry, and water is a key component of habitability on Earth and for likely other habitable environments in the solar system. While water is ubiquitous in the interstellar medium, and plays a key role in protoplanetary disk chemistry, the inner solar system is relatively dry. We now have evidence for potentially thousands of extrasolar planets, dozens of which may be located in their host stars habitable zones. Understanding how planets in the habitable zone accrete their water, is key to understanding the likelihood for habitability. Given that many disk models show that Earth formed inside the water-ice snow line of our solar system, understanding how the inner solar system received its water is important for understanding the potential for other planetary systems to host habitable worlds. Boundaries for the timing of the water delivery are constrained by cosmochemistry and geochemistry. Possible scenarios for the delivery of water to the inner solar system include adsorption on dust from protoplanetary disk gas, chemical reactions on the early earth, and delivery from planetesimals forming outside the water-ice snow line. This talk will set the stage for understanding the isotopic and geochemical markers along with the dynamical delivery mechanisms that will help uncover the origins of Earths water. This introduction will provide an overview for understanding the distribution of water in the solar system, in particular for the inner solar system and terrestrial planets Xand the details will be developed in the subsequent talks. Additionally information will be presented regarding new inner solar system reservoirs of water that can shed light on origins (the main belt comets), and new research about water in the Earth.
Comparative Studies of the Dust around Red Supergiant and Oxygen-Rich Asymptotic Giant Branch Stars in the Local Universe
Authors: Sargent B. A. , Srinivasan S. , Speck A. , Volk K. , Kemper F. , Reach W. , Lagadec E. , Bernard J.-P. , McDonald I. , Meixner M. , Sloan G. C. , Jones O. 
Published: October 2016

AbstractWe analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.
Revisiting the red supergiant progenitors of core-collapse supernovae
Authors: Van Dyk Schuyler D. 
Published: October 2016

AbstractI will present a reanalysis of the properties of the red supergiant (RSG) progenitors of several extragalactic core-collapse, Type II-Plateau supernovae, including SN 2012aw, SN 2013ej, SN 2004et, and SN 2008bk. The observed spectral energy distributions (SEDs) for these stars, from the optical to the infrared, are compared with model SEDs for Galactic RSGs, as well as with the observed SEDs of analogous RSGs in Local Group galaxies. As a result, new estimates of the stellar temperatures and luminosities for the progenitors are obtained, and through comparison with recent massive stellar evolutionary tracks, new inferences are made for the progenitors initial masses. I will place these in the context of the RSG SN progenitor mass spectrum and of the so-called “red supergiant problem.”
Cool Stars in the Hertzsprung–Russell Diagram
Authors: van Loon Jacco Th. 
Published: October 2016

AbstractAs the opening review to the focus meeting “Stellar Behemoths: Red Supergiants across the Local Universe”, I here provide a brief introduction to red supergiants, setting the stage for subsequent contributions. I highlight some recent activity in the field, and identify areas of progress, areas where progress is needed, and how such progress might be achieved.
The Kepler field of view covered with the LAMOST spectroscopic observations
Authors: Molenda-Żakowicz Joanna , De Cat Peter , Fu Jian-Ning , Ren An-Bing , Frasca Antonio , Catanzaro Giovanni 
Published: October 2016

AbstractThe Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) at the Xinglong observatory in China is a 4-m telescope equipped with 4,000 optical fibres. In 2010, we initiated the LAMOST-Kepler project which aimed at collecting low-resolution spectra of stars from the Kepler Input Catalog covering uniformly the Kepler field of view. The first round of the LAMOST-Kepler project has been completed in September 2014 resulting in more than 100,000 low-resolution spectra. We used those data to derive the effective temperature, the surface gravity, and the mean metallicity of our targets, as well as to detect fast rotators, and to identify emission-line stars. Our results are consistent with those reported in the literature and derived from high-resolution spectroscopy. The second round of the LAMOST-Kepler project will allow to improve the coverage of the Kepler field and to repeat observations of selected targets.
Theory of stellar convection: removing the mixing-length parameter
Authors: Pasetto Stefano , Chiosi Cesare , Cropper Mark , Grebel Eva K. 
Published: October 2016

AbstractStellar convection is customarily described by the mixing-length theory, which makes use of the mixing-length scale to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun. No strong arguments exist to suggest that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in the literature are hampered by this basic uncertainty.In a recent paper (Pasettoet al.2014) we presented a new theory that does not require the mixing length parameter. Our self-consistent analytical formulation of stellar convection determines all the properties of stellar convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium. The new theory of stellar convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of stellar convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time-dependent formalism.We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory are compared with those from the standard mixing-length paradigm with positive results for atmosphere models of the Sun and all the stars in the Hertzsprung-Russell diagram.