Search Publications
Major mergers are not significant drivers of star formation or morphological transformation around the epoch of peak cosmic star formation
Conselice, C. J.; Hartley, W.; Mortlock, A. +2 more
We investigate the contribution of major mergers (mass ratios >1: 5) to stellar mass growth and morphological transformations around the epoch of peak cosmic star formation (z ∼ 2). We visually classify a complete sample of massive (M > 1010M⊙) galaxies at this epoch, drawn from the Cosmic Assembly Near-infrared Deep Ex…
Modeling the Historical Flux of Planetary Impactors
Nesvorný, David; Roig, Fernando; Bottke, William F.
The impact cratering record of the Moon and the terrestrial planets provides important clues about the formation and evolution of the solar system. Especially intriguing is the epoch ≃3.8-3.9 Gyr ago (Ga), known as the Late Heavy Bombardment (LHB), when the youngest lunar basins such as Imbrium and Orientale formed. The LHB was suggested to origin…
VoIgt profile Parameter Estimation Routine (viper): H I photoionization rate at z < 0.5
Khaire, Vikram; Srianand, Raghunathan; Choudhury, Tirthankar Roy +1 more
We have developed a parallel code called the VoIgt profile Parameter Estimation Routine (viper) for automatically fitting the H I Lyα forest seen in the spectra of quasi-stellar objects (QSOs). We obtained the H I column density distribution function (CDDF) and linewidth (b) parameter distribution for z < 0.45 using spectra of 82 QSOs obtained …
Cosmic viscosity as a remedy for tension between PLANCK and LSS data
Anand, Sampurn; Chaubal, Prakrut; Mazumdar, Arindam +1 more
Measurements of σ8 from large scale structure observations show a discordance with the extrapolated σ8 from Planck CMB parameters using ΛCDM cosmology. Similar discordance is found in the value of H0 and Ωm. In this paper, we show that the presence of viscosity, shear or bulk or combination of both, can …
Elongation of Flare Ribbons
Qiu, Jiong; Longcope, Dana W.; Cassak, Paul A. +1 more
We present an analysis of the apparent elongation motion of flare ribbons along the polarity inversion line (PIL), as well as the shear of flare loops in several two-ribbon flares. Flare ribbons and loops spread along the PIL at a speed ranging from a few to a hundred km s-1. The shear measured from conjugate footpoints is consistent wi…
Different Origins or Different Evolutions? Decoding the Spectral Diversity Among C-type Asteroids
Jorda, L.; Lamy, P.; Groussin, O. +15 more
Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been proposed as surface analogs for about two-thirds of all C-complex asteroids. However, this suggestion appears to be inconsistent with the presence of hydrated silicates on the surfaces of some of these asteroids, including Ceres. Here, we report the presence of enstatite (pyrox…
LISA pathfinder appreciably constrains collapse models
Slagmolen, B. J. J.; Helou, Bassam; McClelland, David E. +1 more
Spontaneous collapse models are phenomological theories formulated to address major difficulties in macroscopic quantum mechanics. We place significant bounds on the parameters of the leading collapse models, the continuous spontaneous localization (CSL) model, and the Diosi-Penrose (DP) model, by using LISA Pathfinder's measurement, at a record a…
On the progenitor of the Type IIb supernova 2016gkg
Treu, Tommaso; Kilpatrick, Charles D.; Foley, Ryan J. +7 more
We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck adaptive optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source …
Evidence that the AGN dominates the radio emission in z ∼ 1 radio-quiet quasars
Jarvis, Matt J.; Kalfountzou, Eleni; White, Sarah V. +4 more
In order to understand the role of radio-quiet quasars (RQQs) in galaxy evolution, we must determine the relative levels of accretion and star-formation activity within these objects. Previous work at low radio flux densities has shown that accretion makes a significant contribution to the total radio emission, in contrast with other quasar studie…
Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the Warm Hypergiants: How to Tell Them Apart
Humphreys, Roberta M.; Gordon, Michael S.; Martin, John C. +2 more
In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe II emission line stars, the B[e] supergiants, and the warm hype…