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Monthly Notices of the Royal Astronomical Society

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https://www.readbyqxmd.com/read/30008487/maximally-rotating-supermassive-stars-at-the-onset-of-collapse-the-perturbative-effects-of-gas-pressure-magnetic-fields-dark-matter-and-dark-energy
#1
Satya P Butler, Alicia R Lima, Thomas W Baumgarte, Stuart L Shapiro
The discovery of quasars at increasingly large cosmological redshifts may favour 'direct collapse' as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors - supermassive stars - become unstable to gravitational collapse. For uniformly rotating stars supported by pure radiation pressure and spinning at the mass-shedding limit, the critical configuration at the onset of collapse is characterized by universal values of the dimensionless spin and radius parameters J / M 2 and R / M , independent of mass M ...
July 2018: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/30197453/astrochemical-evolution-along-star-formation-overview-of-the-iram-large-program-asai
#2
Bertrand Lefloch, R Bachiller, C Ceccarelli, J Cernicharo, C Codella, A Fuente, C Kahane, A López-Sepulcre, M Tafalla, C Vastel, E Caux, M González-García, E Bianchi, A Gómez-Ruiz, J Holdship, E Mendoza, J Ospina-Zamudio, L Podio, D Quénard, E Roueff, N Sakai, S Viti, S Yamamoto, K Yoshida, C Favre, T Monfredini, H M Quitián-Lara, N Marcelino, H M Boechat-Roberty, S Cabrit
Evidence is mounting that the small bodies of our Solar System, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar System formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program "Astrochemical Surveys At IRAM" (ASAI)...
April 14, 2018: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/29545651/activity-of-the-2013-geminid-meteoroid-stream-at-the-moon
#3
Jamey R Szalay, Petr Pokorný, Peter Jenniskens, Mihály Horányi
The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer mission orbited the Moon from 2013 October to 2014 April and detected impact ejecta generated by the continual bombardment of meteoroids to the lunar surface. While the Moon transited the Geminid meteoroid stream, LDEX observed a large enhancement in the lunar impact ejecta cloud, particularly above the portion of lunar surface normal to the Geminids radiant. Here, we present the LDEX measurements during the Geminids, using the surface density of impact ejecta at the Moon as a proxy for meteoroid activity...
March 2018: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/29755143/likely-transiting-exocomets-detected-by-kepler
#4
S Rappaport, A Vanderburg, T Jacobs, D LaCourse, J Jenkins, A Kraus, A Rizzuto, D W Latham, A Bieryla, M Lazarevic, A Schmitt
We present the first good evidence for exocomet transits of a host star in continuum light in data from the Kepler mission. The Kepler star in question, KIC 3542116, is of spectral type F2V and is quite bright at Kp = 10. The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk. There are three deeper transits with depths of ≃ 0.1% that last for about a day, and three that are several times more shallow and of shorter duration...
February 21, 2018: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28983129/galaxy-formation-with-becdm-i-turbulence-and-relaxation-of-idealized-haloes
#5
Philip Mocz, Mark Vogelsberger, Victor H Robles, Jesús Zavala, Michael Boylan-Kolchin, Anastasia Fialkov, Lars Hernquist
We present a theoretical analysis of some unexplored aspects of relaxed Bose-Einstein condensate dark matter (BECDM) haloes. This type of ultralight bosonic scalar field dark matter is a viable alternative to the standard cold dark matter (CDM) paradigm, as it makes the same large-scale predictions as CDM and potentially overcomes CDM's small-scale problems via a galaxy-scale de Broglie wavelength. We simulate BECDM halo formation through mergers, evolved under the Schrödinger-Poisson equations. The formed haloes consist of a soliton core supported against gravitational collapse by the quantum pressure tensor and an asymptotic r -3 NFW-like profile...
November 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/29861511/laboratory-study-of-methyl-isocyanate-ices-under-astrophysical-conditions
#6
B Maté, G Molpeceres, V Timón, I Tanarro, R Escribano, J C Guillemin, J Cernicharo, V J Herrero
Methyl isocyanate has been recently detected in comet 67P/ Churyumov-Gerasimenko (67P/CG) and in the interstellar medium. New physicochemical studies on this species are now necessary as tools for subsequent studies in astrophysics. In this work, infrared spectra of solid CH3 NCO have been obtained at temperatures of relevance for astronomical environments. The spectra are dominated by a strong, characteristic multiplet feature at 2350-2250 cm-1 , which can be attributed to the antisymmetric stretching of the NCO group...
October 1, 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/29142332/the-interstellar-chemistry-of-c-3-h-and-c-3-h-2-isomers
#7
Jean-Christophe Loison, Marcelino Agúndez, Valentine Wakelam, Evelyne Roueff, Pierre Gratier, Núria Marcelino, Dianailys Nuñez Reyes, José Cernicharo, Maryvonne Gerin
We report the detection of linear and cyclic isomers of C3 H and C3 H2 towards various starless cores and review the corresponding chemical pathways involving neutral (C3 Hx with x=1,2) and ionic (C3 Hx + with x = 1,2,3) isomers. We highlight the role of the branching ratio of electronic Dissociative Recombination (DR) reactions of C3 H2 + and C3 H3 + isomers showing that the statistical treatment of the relaxation of C3 H* and C3 H2 * produced in these DR reactions may explain the relative c,l-C3 H and c,l-C3 H2 abundances...
October 1, 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28690343/state-to-state-chemistry-and-rotational-excitation-of-ch-in-photon-dominated-regions
#8
A Faure, P Halvick, T Stoecklin, P Honvault, M D Epée Epée, J Zs Mezei, O Motapon, I F Schneider, J Tennyson, O Roncero, N Bulut, A Zanchet
We present a detailed theoretical study of the rotational excitation of CH(+) due to reactive and nonreactive collisions involving C(+)((2)P), H2, CH(+), H and free electrons. Specifically, the formation of CH(+) proceeds through the reaction between C(+)((2)P) and H2(νH2 = 1, 2), while the collisional (de)excitation and destruction of CH(+) is due to collisions with hydrogen atoms and free electrons. State-to-state and initial-state-specific rate coefficients are computed in the kinetic temperature range 10-3000 K for the inelastic, exchange, abstraction and dissociative recombination processes using accurate potential energy surfaces and the best scattering methods...
July 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28607526/a-unified-framework-for-constructing-tuning-and-assessing-photometric-redshift-density-estimates-in-a-selection-bias-setting
#9
P E Freeman, R Izbicki, A B Lee
Photometric redshift estimation is an indispensable tool of precision cosmology. One problem that plagues the use of this tool in the era of large-scale sky surveys is that the bright galaxies that are selected for spectroscopic observation do not have properties that match those of (far more numerous) dimmer galaxies; thus, ill-designed empirical methods that produce accurate and precise redshift estimates for the former generally will not produce good estimates for the latter. In this paper, we provide a principled framework for generating conditional density estimates (i...
July 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28579644/complex-organic-molecules-tracing-shocks-along-the-outflow-cavity-in-the-high-mass-protostar-iras-20126-4104
#10
Aina Palau, Catherine Walsh, Álvaro Sánchez-Monge, Josep M Girart, Riccardo Cesaroni, Izaskun Jiménez-Serra, Asunción Fuente, Luis A Zapata, Roberto Neri
We report on subarcsecond observations of complex organic molecules (COMs) in the high-mass protostar IRAS 20126+4104 with the Plateau de Bure Interferometer in its most extended configurations. In addition to the simple molecules SO, HNCO and H2(13)CO, we detect emission from CH3CN, CH3OH, HCOOH, HCOOCH3, CH3OCH3, CH3CH2CN, CH3COCH3, NH2CN, and (CH2OH)2. SO and HNCO present a X-shaped morphology consistent with tracing the outflow cavity walls. Most of the COMs have their peak emission at the putative position of the protostar, but also show an extension towards the south(east), coinciding with an H2 knot from the jet at about 800-1000 au from the protostar...
June 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28066154/measuring-the-2d-baryon-acoustic-oscillation-signal-of-galaxies-in-wigglez-cosmological-constraints
#11
Samuel R Hinton, Eyal Kazin, Tamara M Davis, Chris Blake, Sarah Brough, Matthew Colless, Warrick J Couch, Michael J Drinkwater, Karl Glazebrook, Russell J Jurek, David Parkinson, Kevin A Pimbblet, Gregory B Poole, Michael Pracy, David Woods
We present results from the 2D anisotropic baryon acoustic oscillation (BAO) signal present in the final data set from the WiggleZ Dark Energy Survey. We analyse the WiggleZ data in two ways: first using the full shape of the 2D correlation function and secondly focusing only on the position of the BAO peak in the reconstructed data set. When fitting for the full shape of the 2D correlation function we use a multipole expansion to compare with theory. When we use the reconstructed data we marginalize over the shape and just measure the position of the BAO peak, analysing the data in wedges separating the signal along the line of sight from that parallel to the line of sight...
February 1, 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27559304/the-winds-from-hl-tau
#12
P D Klaassen, J C Mottram, L T Maud, A Juhasz
Outflowing motions, whether a wind launched from the disc, a jet launched from the protostar, or the entrained molecular outflow, appear to be a ubiquitous feature of star formation. These outwards motions have a number of root causes, and how they manifest is intricately linked to their environment as well as the process of star formation itself. Using the Atacama Large Millimeter/submillimeter Array (ALMA) Science Verification data of HL Tau, we investigate the high-velocity molecular gas being removed from the system as a result of the star formation process...
July 21, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279787/forming-supermassive-black-hole-seeds-under-the-influence-of-a-nearby-anisotropic-multifrequency-source
#13
John A Regan, Peter H Johansson, John H Wise
The photodissociation of H2 by a nearby anisotropic source of radiation is seen as a critical component in creating an environment in which a direct collapse black hole may form. Employing radiative transfer we model the effect of multifrequency (0.76-60 eV) radiation on a collapsing halo at high redshift. We vary both the shape of the spectrum which emits the radiation and the distance to the emitting galaxy. We use blackbody spectra with temperatures of T = 10(4) K and 10(5) K and a realistic stellar spectrum...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279786/direct-collapse-to-supermassive-black-hole-seeds-comparing-the-amr-and-sph-approaches
#14
Yang Luo, Kentaro Nagamine, Isaac Shlosman
We provide detailed comparison between the adaptive mesh refinement (AMR) code enzo-2.4 and the smoothed particle hydrodynamics (SPH)/N-body code gadget-3 in the context of isolated or cosmological direct baryonic collapse within dark matter (DM) haloes to form supermassive black holes. Gas flow is examined by following evolution of basic parameters of accretion flows. Both codes show an overall agreement in the general features of the collapse; however, many subtle differences exist. For isolated models, the codes increase their spatial and mass resolutions at different pace, which leads to substantially earlier collapse in SPH than in AMR cases due to higher gravitational resolution in gadget-3...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279785/new-methods-to-constrain-the-radio-transient-rate-results-from-a-survey-of-four-fields-with-lofar
#15
D Carbone, A J van der Horst, R A M J Wijers, J D Swinbank, A Rowlinson, J W Broderick, Y N Cendes, A J Stewart, M E Bell, R P Breton, S Corbel, J Eislöffel, R P Fender, J-M Grießmeier, J W T Hessels, P Jonker, M Kramer, C J Law, J C A Miller-Jones, M Pietka, L H A Scheers, B W Stappers, J van Leeuwen, R Wijnands, M Wise, P Zarka
We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg(2). We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279784/modelling-galaxy-clustering-halo-occupation-distribution-versus-subhalo-matching
#16
Hong Guo, Zheng Zheng, Peter S Behroozi, Idit Zehavi, Chia-Hsun Chuang, Johan Comparat, Ginevra Favole, Stefan Gottloeber, Anatoly Klypin, Francisco Prada, Sergio A Rodríguez-Torres, David H Weinberg, Gustavo Yepes
We model the luminosity-dependent projected and redshift-space two-point correlation functions (2PCFs) of the Sloan Digital Sky Survey (SDSS) Data Release 7 Main galaxy sample, using the halo occupation distribution (HOD) model and the subhalo abundance matching (SHAM) model and its extension. All the models are built on the same high-resolution N-body simulations. We find that the HOD model generally provides the best performance in reproducing the clustering measurements in both projected and redshift spaces...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279783/the-minimum-mass-of-detectable-planets-in-protoplanetary-discs-and-the-derivation-of-planetary-masses-from-high-resolution-observations
#17
Giovanni P Rosotti, Attila Juhasz, Richard A Booth, Cathie J Clarke
We investigate the minimum planet mass that produces observable signatures in infrared scattered light and submillimetre (submm) continuum images and demonstrate how these images can be used to measure planet masses to within a factor of about 2. To this end, we perform multi-fluid gas and dust simulations of discs containing low-mass planets, generating simulated observations at 1.65, 10 and 850 μm. We show that the minimum planet mass that produces a detectable signature is ∼15 M⊕: this value is strongly dependent on disc temperature and changes slightly with wavelength (favouring the submm)...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279782/low-radio-frequency-eclipses-of-the-redback-pulsar-j2215-5135-observed-in-the-image-plane-with-lofar
#18
J W Broderick, R P Fender, R P Breton, A J Stewart, A Rowlinson, J D Swinbank, J W T Hessels, T D Staley, A J van der Horst, M E Bell, D Carbone, Y Cendes, S Corbel, J Eislöffel, H Falcke, J-M Grießmeier, T E Hassall, P Jonker, M Kramer, M Kuniyoshi, C J Law, S Markoff, G J Molenaar, M Pietka, L H A Scheers, M Serylak, B W Stappers, S Ter Veen, J van Leeuwen, R A M J Wijers, R Wijnands, M W Wise, P Zarka
The eclipses of certain types of binary millisecond pulsars (i.e. 'black widows' and 'redbacks') are often studied using high-time-resolution, 'beamformed' radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of two weeks - six months, we find preliminary evidence that the eclipse duration is frequency dependent (∝ν(-0...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27279781/modelling-accretion-disc-and-stellar-wind-interactions-the-case-of-sgr-a
#19
I M Christie, M Petropoulou, P Mimica, D Giannios
Sgr A* is an ideal target to study low-luminosity accreting systems. It has been recently proposed that properties of the accretion flow around Sgr A* can be probed through its interactions with the stellar wind of nearby massive stars belonging to the S-cluster. When a star intercepts the accretion disc, the ram and thermal pressures of the disc terminate the stellar wind leading to the formation of a bow shock structure. Here, a semi-analytical model is constructed which describes the geometry of the termination shock formed in the wind...
July 1, 2016: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/27274704/the-different-baryonic-tully-fisher-relations-at-low-masses
#20
Chris B Brook, Isabel Santos-Santos, Greg Stinson
We compare the Baryonic Tully-Fisher relation (BTFR) of simulations and observations of galaxies ranging from dwarfs to spirals, using various measures of rotational velocity V rot. We explore the BTFR when measuring V rot at the flat part of the rotation curve, V flat, at the extent of H i gas, V last, and using 20 per cent (W 20) and 50 per cent (W 50) of the width of H i line profiles. We also compare with the maximum circular velocity of the parent halo, [Formula: see text], within dark matter only simulations...
June 11, 2016: Monthly Notices of the Royal Astronomical Society
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