Search Publications
The Quasar Luminosity Function at z 5 via Deep Learning and Bayesian Information Criterion
Im, Myungshin; Shin, Suhyun; Kim, Yongjung
Understanding the faint end of quasar luminosity function (LF) at a high redshift is important since the number density of faint quasars is a critical element in constraining ultraviolet (UV) photon budgets for ionizing the intergalactic medium (IGM) in the early universe. Here, we present quasar LF reaching M 1450 ~ -22.0 AB mag at z ~…
The Impact of Inelastic Collisions with Hydrogen on NLTE Copper Abundances in Metal-poor Stars
Shi, Jianrong; Wang, Xiaofeng; Xu, Xiaodong
We investigate the non-local thermodynamic equilibrium (non-LTE, hereafter NLTE) analysis for Cu I lines with the updated model atom that includes quantum-mechanical rate coefficients of Cu + H and Cu+ + H- inelastic collisions from the recent study of Belyaev et al. The influence of these data on NLTE abundance determination…
CAHA/PPAK Integral-field Spectroscopic Observations of M81. I. Circumnuclear Ionized Gas
Li, Zhiyuan; García-Benito, Rubén; Li, Zongnan +1 more
Galactic circumnuclear environments of nearby galaxies provide unique opportunities for our understanding of the coevolution between supermassive black holes and their host galaxies. Here, we present a detailed study of ionized gas in the central kiloparsec region of M81, which hosts the closest prototype low-luminosity active galactic nucleus, ba…
Gas Dynamics in the Star-forming Region G18.148-0.283: Is It a Manifestation of Two Colliding Molecular Clouds?
Dey, Jyotirmoy; Pandian, Jagadheep D.; Lal, Dharam Vir
We report the results obtained from a multiwavelength study of the H II region G18.148-0.283 using the upgraded Giant Metrewave Radio Telescope at 1350 MHz, along with other archival data. In addition to the radio continuum emission, we have detected the H169α and H170α radio recombination lines toward G18.148-0.283 using a correlator bandwidth of…
The Expansion of the X-Ray Nebula Around η Car
Corcoran, Michael F.; Russell, C. M. P.; Hamaguchi, K. +8 more
The massive colliding wind binary system η Car is embedded in an X-ray emitting region having a characteristic temperature of a few million degrees, associated with ejecta produced during the 1840s, and in earlier outbursts. We use CHANDRA X-ray imaging observations obtained over the past two decades to directly measure the expansion of the X-ray …
The Warm Gas in the Milky Way: The Kinematical Model of C IV and Its Connection to Si IV
Bregman, Joel N.; Qu, Zhijie; Lindley, Ryan
We compose a 265-sight-line Milky Way C IV line-shape sample using the Hubble Space Telescope/Cosmic Origins Spectrograph archive, which is complementary to the existing Si IV samples. C IV has a higher ionization potential (47-64 eV) than Si IV (33-45 eV), so it also traces warm gas, which is roughly cospatial with Si IV. The spatial density dist…
Tracing the Giant Outer Halo of the Mysterious Massive Disk Galaxy M104. I. Photometry of the Extended Globular Cluster Systems
Park, Byeong-Gon; Hwang, Narae; Lee, Myung Gyoon +4 more
M104 (NGC 4594, the Sombrero galaxy) is a mysterious massive early-type galaxy that shows a dominant bulge and a prominent disk. However, the presence of a halo in M104 has been elusive, and it is not yet known how M104 has acquired such a peculiar structure. Using wide (~2 deg2) and deep ugi images of M104 obtained with the CFHT/MegaCa…
A Volumetric Study of Flux Transfer Events at the Dayside Magnetopause
Strugarek, Antoine; Vaidya, Bhargav; Paul, Arghyadeep
Localized magnetic reconnection at the dayside magnetopause leads to the production of Flux Transfer Events (FTEs). The magnetic fields within the FTEs exhibit complex helical flux-rope topologies. Leveraging the adaptive mesh refinement strategy, we perform a three-dimensional magnetohydrodynamic simulation of the magnetosphere of an Earth-like p…
Substructure at High Speed. I. Inferring the Escape Velocity in the Presence of Kinematic Substructure
Necib, Lina; Lin, Tongyan
The local escape velocity provides valuable inputs to the mass profile of the galaxy, and requires understanding the tail of the stellar speed distribution. Following Leonard & Tremaine, various works have since modeled the tail of the stellar speed distribution as $\propto {({v}_{\mathrm{esc}}-v)}^{k}$ , where v esc is the escape v…
Deep Upper Limit on the Optical Emission during a Hard X-Ray Burst from the Magnetar SGR J1935+2154
Naletto, Giampiero; Burtovoi, Aleksandr; Mereghetti, Sandro +9 more
In 2021 September the magnetar SGR J1935+2154 entered a stage of burst/flaring activity in the hard X-ray band. On 2021 September 10, we observed SGR J1935+2154 with the fiber-fed fast optical photon counter IFI+Iqueye, mounted at the 1.22 m Galileo telescope in Asiago. During one of the IFI+Iqueye observing windows, a hard X-ray burst was detecte…