Search Publications
Development of Hydrogen and Helium Proximity Zones around Quasars
Zheng, Wei; Meiksin, Avery; Syphers, David
Increasing evidence suggests that He II proximity profiles in the quasar spectra at z ∼ 3-4 are sensitive probes of quasar ages. But the development of their H I counterparts is difficult to trace and remains poorly constrained. We compare the UV spectra of 15 He II quasars with their high-resolution optical counterparts and find a significant cor…
Gravitational Lens System PS J0147+4630 (Andromeda’s Parachute): Main Lensing Galaxy and Optical Variability of the Quasar Images
Goicoechea, Luis J.; Shalyapin, Vyacheslav N.
Because follow-up observations of quadruple gravitational lens systems are of extraordinary importance for astrophysics and cosmology, we present single-epoch optical spectra and r-band light curves of PS J0147+4630. This recently discovered system mainly consists of four images ABCD of a background quasar around a foreground galaxy G that acts as…
A Study of the Merger History of the Galaxy Group HCG 62 Based on X-Ray Observations and Smoothed Particle Hydrodynamic Simulations
Hu, Dan; Xu, Haiguang; Zhu, Zhenghao +9 more
We chose the bright compact group HCG 62, which has been found to exhibit both excess X-ray emission and high Fe abundance to the southwest of its core, as an example to study the impact of mergers on chemical enrichment in the intragroup medium. We first reanalyze the high-quality Chandra and XMM-Newton archive data to search for evidence of addi…
Quasars Have Fewer Close Companions than Normal Galaxies
Fan, Xiaohui; McGreer, Ian D.; Huang, Yun-Hsin +2 more
We investigate the distribution of companion galaxies around quasars using Hubble Space Telescope (HST) Advanced Camera for Surveys Wide Field Camera (ACS/WFC) archival images. Our master sample contains 532 quasars that have been observed by HST ACS/WFC, spanning a wide range of luminosity (-31 < M i (z = 2) < -23) and redshift …
Spectrophotometric Redshifts for z ∼ 1 Galaxies and Predictions for Number Densities with WFIRST and Euclid
Hathi, Nimish P.; Cohen, Seth; Windhorst, Rogier A. +3 more
We investigate the accuracy of 4000 Å/Balmer-break based redshifts by combining Hubble Space Telescope (HST) grism data with photometry. The grism spectra are from the Probing Evolution And Reionization Spectroscopically survey with HST using the G800L grism on the Advanced Camera for Surveys. The photometric data come from a compilation by the 3D…
Infrared Galaxies in the Field of the Massive Cluster Abell S1063: Discovery of a Luminous Kiloparsec-sized H II Region in a Gravitationally Lensed Infrared-luminous Galaxy at z = 0.6
Richard, Johan; Weiner, Benjamin; Egami, Eiichi +10 more
Using the Spitzer Space Telescope and Herschel Space Observatory, we have conducted a survey of IR galaxies in the field of the galaxy cluster AS1063 at z = 0.347, which is one of the most massive clusters known and a target of the Hubble Space Telescope (HST) Cluster Lensing and Supernova Survey with Hubble and the Frontier Field surveys. The Spi…
The Nature of Class I Sources: Periodic Variables in Orion
Duchene, Gaspard; Ellithorpe, Elizabeth A.; Stahler, Steven W.
We present a quantitative, empirically based argument that at least some Class I sources are low-mass, pre-main-sequence stars surrounded by spatially extended envelopes of dusty gas. The source luminosity arises principally from stellar gravitational contraction, as in optically visible pre-main-sequence stars that lack such envelopes. We base ou…
Hunting Young White Dwarfs at the Center of Planetary Nebulae
Weidmann, Walter A.; Ahumada, Javier A.; Miller Bertolami, Marcelo M. +1 more
We present Gemini-South observations of nine faint and extended planetary nebulae (PNe). Using direct images taken with the spectrograph Gemini-South multi-object spectrograph (GMOS), we built the (u\prime -g\prime ) versus (g\prime -r\prime ) diagrams of the stars in the observed areas which allowed us …
Integrated Spectra of Milky Way Globular Clusters
Trevisan, M.; Barbuy, B.; Moura, T. C. +1 more
Integrated spectra of Milky Way globular clusters (GCs) are reproduced by computing synthetic spectra taking into account individual element abundances. Five clusters were selected from their location in the Galactic bulge, for which integrated spectra were available in the WiFeS Atlas of Galactic Globular Cluster Spectra project. Our aim is to fu…
Relativistic Astronomy. II. In-flight Solution of Motion and Test of Special Relativity Light Aberration
Zhang, Bing; Yang, Yuan-Pei; Zhu, Jin-Ping
The Breakthrough Starshot project aims to send centimeter-sized, gram-scale “StarChip” probes to Alpha Centauri at a speed of ∼0.2 c. On the other hand, Zhang & Li recently proposed that transrelativistic cameras may be sent to any direction to study astronomical objects and test special relativity. To conduct such “relativistic astronomy,” on…