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Monthly Notices of the Royal Astronomical Society

Yen-Chi Chen, Shirley Ho, Jonathan Blazek, Siyu He, Rachel Mandelbaum, Peter Melchior, Sukhdeep Singh
Previous studies have shown the filamentary structures in the cosmic web influence the alignments of nearby galaxies. We study this effect in the LOWZ sample of the Sloan Digital Sky Survey using the 'Cosmic Web Reconstruction' filament catalogue. We find that LOWZ galaxies exhibit a small but statistically significant alignment in the direction parallel to the orientation of nearby filaments. This effect is detectable even in the absence of nearby galaxy clusters, which suggests it is an effect from the matter distribution in the filament...
May 2019: Monthly Notices of the Royal Astronomical Society
Mark R Krumholz, Angela Adamo, Michele Fumagalli, Daniela Calzetti
We describe a novel method for determining the demographics of a population of star clusters, for example distributions of cluster mass and age, from unresolved photometry. This method has a number of desirable properties: it fully exploits all the information available in a data set without any binning, correctly accounts for both measurement error and sample incompleteness, naturally handles heterogenous data (e.g. fields that have been imaged with different sets of filters or to different depths), marginalizes over uncertain extinctions, and returns the full posterior distributions of the parameters describing star cluster demographics...
January 2019: Monthly Notices of the Royal Astronomical Society
Shea Garrison-Kimmel, Philip F Hopkins, Andrew Wetzel, Kareem El-Badry, Robyn E Sanderson, James S Bullock, Xiangcheng Ma, Freeke van de Voort, Zachary Hafen, Claude-André Faucher-Giguère, Christopher C Hayward, Eliot Quataert, Dušan Kereš, Michael Boylan-Kolchin
We use hydrodynamic cosmological zoom-in simulations from the Feedback in Realistic Environments project to explore the morphologies and kinematics of 15 Milky Way (MW)-mass galaxies. Our sample ranges from compact, bulge-dominated systems with 90 per cent of their stellar mass within 2.5 kpc to well-ordered discs that reach ≳15 kpc. The gas in our galaxies always forms a thin, rotation-supported disc at z = 0, with sizes primarily determined by the gas mass. For stars, we quantify kinematics and morphology both via the fraction of stars on disc-like orbits and with the radial extent of the stellar disc...
December 11, 2018: Monthly Notices of the Royal Astronomical Society
Paul Carter, Florian Beutler, Will J Percival, Chris Blake, Jun Koda, Ashley J Ross
Low-redshift measurements of baryon acoustic oscillations (BAO) measure the late-time evolution of the Universe and are a vital probe of dark energy. Over the past decade both the 6-degree Field Galaxy Survey (6dFGS) and Sloan Digital Sky Survey Main Galaxy Sample (SDSS MGS) have provided important distance constraints at [Formula: see text] < 0.3. In this paper we re-evaluate the cosmological information from the BAO detection in 6dFGS making use of halo occupation distribution (HOD)-populated COmoving Lagrangian Acceleration (COLA) mocks for an accurate covariance matrix and take advantage of the now commonly implemented technique of density field reconstruction...
December 2018: Monthly Notices of the Royal Astronomical Society
Michael Y Grudić, Dávid Guszejnov, Philip F Hopkins, Astrid Lamberts, Michael Boylan-Kolchin, Norman Murray, Denise Schmitz
Young massive star clusters spanning ~104 -108 M⊙ in mass have been observed to have similar surface brightness profiles. We show that recent hydrodynamical simulations of star cluster formation have also produced star clusters with this structure. We argue analytically that this type of mass distribution arises naturally in the relaxation from a hierarchically clustered distribution of stars into a monolithic star cluster through hierarchical merging. We show that initial profiles of finite maximum density will tend to produce successively shallower power-law profiles under hierarchical merging, owing to certain conservation constraints on the phase-space distribution...
November 2018: Monthly Notices of the Royal Astronomical Society
Kung-Yi Su, Philip F Hopkins, Christopher C Hayward, Xiangcheng Ma, Michael Boylan-Kolchin, Daniel Kasen, Dušan Kereš, Claude-André Faucher-Giguère, Matthew E Orr, Coral Wheeler
Using high-resolution simulations from the FIRE-2 (Feedback In Realistic Environments) project, we study the effects of discreteness in stellar feedback processes on the evolution of galaxies and the properties of the interstellar medium (ISM). We specifically consider the discretization of supernovae (SNe), including hypernovae (HNe), and sampling the initial mass function (IMF). We study these processes in cosmological simulations of dwarf galaxies with z = 0 stellar masses M * ~ 104 -3 × 106 M⊙ (halo masses ~109 -1010 M⊙ )...
October 2018: Monthly Notices of the Royal Astronomical Society
Kareem El-Badry, Joss Bland-Hawthorn, Andrew Wetzel, Eliot Quataert, Daniel R Weisz, Michael Boylan-Kolchin, Philip F Hopkins, Claude-André Faucher-Giguère, Dušan Kereš, Shea Garrison-Kimmel
The oldest stars in the Milky Way (MW) bear imprints of the Galaxy's early assembly history. We use FIRE cosmological zoom-in simulations of three MW-mass disc galaxies to study the spatial distribution, chemistry, and kinematics of the oldest surviving stars ( z form ≳ 5) in MW-like galaxies. We predict the oldest stars to be less centrally concentrated at z = 0 than stars formed at later times as a result of two processes. First, the majority of the oldest stars are not formed in situ but are accreted during hierarchical assembly...
October 2018: Monthly Notices of the Royal Astronomical Society
Andrew S Graus, James S Bullock, Michael Boylan-Kolchin, Anna M Nierenberg
A fundamental prediction of the cold dark matter cosmology is the existence of a large number of dark subhalos around galaxies, most of which should be entirely devoid of stars. Confirming the existence of dark substructures stands among the most important empirical challenges in modern cosmology: if they are found and quantified with the mass spectrum expected, then this would close the door on a vast array of competing theories. But in order for observational programs of this kind to reach fruition, we need robust predictions...
October 2018: Monthly Notices of the Royal Astronomical Society
Michael Boylan-Kolchin
Metal-poor globular clusters (GCs) are both numerous and ancient, which indicates that they may be important contributors to ionizing radiation in the reionization era. Starting from the observed number density and stellar mass function of old GCs at z = 0, I compute the contribution of GCs to ultraviolet luminosity functions (UVLFs) in the high-redshift Universe (10 ≳ z ≳ 4). Even under absolutely minimal assumptions - no disruption of GCs and no reduction in GC stellar mass from early times to the present - GC star formation contributes non-negligibly to the UVLF at luminosities that are accessible to the Hubble Space Telescope ( HST , M 1500 ≈ -17)...
September 2018: Monthly Notices of the Royal Astronomical Society
Sean P Fillingham, Michael C Cooper, Michael Boylan-Kolchin, James S Bullock, Shea Garrison-Kimmel, Coral Wheeler
In the local Universe, there is a strong division in the star-forming properties of low-mass galaxies, with star formation largely ubiquitous amongst the field population while satellite systems are predominantly quenched. This dichotomy implies that environmental processes play the dominant role in suppressing star formation within this low-mass regime ( M ★ ~ 105.5-8 M☉ ). As shown by observations of the Local Volume, however, there is a non-negligible population of passive systems in the field, which challenges our understanding of quenching at low masses...
July 11, 2018: Monthly Notices of the Royal Astronomical Society
Mark R Lovell, Jesús Zavala, Mark Vogelsberger, Xuejian Shen, Francis-Yan Cyr-Racine, Christoph Pfrommer, Kris Sigurdson, Michael Boylan-Kolchin, Annalisa Pillepich
We contrast predictions for the high-redshift galaxy population and reionization history between cold dark matter (CDM) and an alternative self-interacting dark matter model based on the recently developed ETHOS framework that alleviates the small-scale CDM challenges within the Local Group. We perform the highest resolution hydrodynamical cosmological simulations (a 36 Mpc3 volume with gas cell mass of ∼ 105 M⊙ and minimum gas softening of ∼ 180 pc) within ETHOS to date - plus a CDM counterpart - to quantify the abundance of galaxies at high redshift and their impact on reionization...
July 1, 2018: Monthly Notices of the Royal Astronomical Society
T K Chan, D Kereš, A Wetzel, P F Hopkins, C-A Faucher-Giguère, K El-Badry, S Garrison-Kimmel, M Boylan-Kolchin
We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin haloes, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius, and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times...
July 2018: Monthly Notices of the Royal Astronomical Society
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
Tom O Zick, Daniel R Weisz, Michael Boylan-Kolchin
We present the reconstructed evolution of rest-frame ultraviolet (UV) luminosities of the most massive Milky Way dwarf spheroidal satellite galaxy, Fornax, and its five globular clusters (GCs) across redshift, based on analysis of the stellar fossil record and stellar population synthesis modelling. We find that (1) Fornax's (proto-)GCs can generate 10-100 times more UV flux than the field population, despite comprising <~ 5 per cent of the stellar mass at the relevant redshifts; (2) due to their respective surface brightnesses, it is more likely that faint, compact sources in the Hubble Frontier Fields (HFFs) are GCs hosted by faint galaxies, than faint galaxies themselves...
June 11, 2018: Monthly Notices of the Royal Astronomical Society
Kareem El-Badry, Jeremy Bradford, Eliot Quataert, Marla Geha, Michael Boylan-Kolchin, Daniel R Weisz, Andrew Wetzel, Philip F Hopkins, T K Chan, Alex Fitts, Dušan Kereš, Claude-André Faucher-Giguére
The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/σ and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations...
June 2018: Monthly Notices of the Royal Astronomical Society
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
Eder Martioli, Knicole D Colón, Daniel Angerhausen, Keivan G Stassun, Joseph E Rodriguez, George Zhou, B Scott Gaudi, Joshua Pepper, Thomas G Beatty, Ramarao Tata, David J James, Jason D Eastman, Paul Anthony Wilson, Daniel Bayliss, Daniel J Stevens
We present near infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precision as low as 0.11%. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously...
March 1, 2018: Monthly Notices of the Royal Astronomical Society
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
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
M de Val-Borro, S N Milam, M A Cordiner, S B Charnley, I M Coulson, A J Remijan, G L Villanueva
Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar System. We report here on millimeter spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between UT 16.948 to 18.120 January 2015, when the comet was at heliocentric distance of 1.30 au and geocentric distance of 0.53 au. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma...
February 11, 2018: Monthly Notices of the Royal Astronomical Society
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