Search Publications
X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields
Sunyaev, R.; Churazov, E.; Federrath, C. +3 more
We take advantage of a set of molecular cloud simulations to demonstrate a possibility to uncover statistical properties of the gas density and velocity fields using reflected emission of a short (with duration much less than the cloud's light-crossing time) X-ray flare. Such a situation is relevant for the Central Molecular Zone (CMZ) of our Gala…
A blazar as the likely counterpart to 4FGL J0647.7-4418 instead of a gamma-ray binary
Corbet, Robin H. D.; Luque-Escamilla, Pedro L.; Martí, Josep +3 more
The persistent gamma-ray source 4FGL J0647.7-4418 is tentatively associated in the latest Fermi catalogue with the subdwarf O-type X-ray binary HD 49798. However, an active galactic nucleus (AGN) candidate is also mentioned as an alternative identification in updated versions of the catalogue accompanying paper. If the first association were corre…
Gravitational potential from small-scale clustering in action space: application to Gaia Data Release 2
Yang, Tianyi; Boruah, Supranta S.; Afshordi, Niayesh
Most measurements of mass in astronomy that use kinematics of stars or gas rely on assumptions of equilibrium that are often hard to verify. Instead, we develop a novel idea that uses the clustering in action space, as a probe of the underlying gravitational potential: the correct potential should maximize small-scale clustering in the action spac…
The distances to molecular clouds in the fourth Galactic quadrant
Wang, Shu; Jiang, Biwei; Chen, Bingqiu +4 more
Distance measurements to molecular clouds are essential and important. We present directly measured distances to 169 molecular clouds in the fourth quadrant of the Milky Way. Based on the near-infrared photometry from the Two Micron All Sky Survey and the Vista Variables in the Via Lactea Survey, we select red clump stars in the overlapping direct…
Structural analysis of disc super star clusters of M82: size and profile shape at intermediate ages
Mayya, Y. D.; Rosa-González, D.; Puerari, I. +1 more
We present the structural parameters of 99 super star clusters (SSCs) in the disc of M82. Moffat-EFF, King, and Wilson models were fitted using a χ2-minimization method to background-subtracted surface brightness profiles in the F435W (B), F555W (V), and F814W (I) bands of the Advanced Camera for Surveys (ACS) of the Hubble Space Telesc…
Detecting neutral hydrogen at z ≳ 3 in large spectroscopic surveys of quasars
Fumagalli, Michele; Fotopoulou, Sotiria; Thomson, Laura
We present a pipeline based on a random forest classifier for the identification of high column density clouds of neutral hydrogen (i.e. the Lyman limit systems, LLSs) in absorption within large spectroscopic surveys of z ≳ 3 quasars. We test the performance of this method on mock quasar spectra that reproduce the expected data quality of the Dark…
Morphology and ionization characteristics of planetary nebulae PB 1 and PC 19
Mondal, Soumen; Das, Ramkrishna; Bandyopadhyay, Rahul +1 more
We present results of our study of two planetary nebulae (PNe), PB1 and PC 19. We use the optical spectra of these two PNe observed at 2 m Himalayan Chandra Telescope and also archival and literature data for the study. We use the morphokinematic code shape to construct 3D morphologies of the PNe and the photoionization code cloudy to model the ob…
Obscuration properties of mid-IR-selected AGN
Georgantopoulos, I.; Mountrichas, G.; Ruiz, A. +1 more
The goal of this work is to study the obscuration properties of mid-infrared (mid-IR)-selected active galactic nuclei (AGN). For that purpose, we use Wide-field Infrared Survey Explorer (WISE) sources in the Stripe 82-XMM area to identify mid-IR AGN candidates, applying the Assef et al. criteria. Stripe 82 has optical photometry ≈2 times deeper th…
The nuclear region of NGC 613 - I. Multiwavelength analysis
Steiner, J. E.; Menezes, R. B.; da Silva, Patrícia
In this paper, we report a detailed study with a variety of data from optical, near-infrared, X-ray, and radio telescopes of the nuclear region of the galaxy NGC 613 with the aim of understanding its complexity. We detected an extended stellar emission in the nucleus that, at first, appears to be, in the optical band, two stellar nuclei separated …
Atacama Compact Array observations of the pulsar-wind nebula of SNR 0540-69.3
Lundqvist, P.; Olofsson, G.; Zyuzin, D. A. +6 more
We present observations of the pulsar-wind nebula (PWN) region of SNR 0540-69.3. The observations were made with the Atacama Compact Array (ACA) in Bands 4 and 6. We also add radio observations from the Australia Compact Array at 3 cm. For 1.449-233.50 GHz, we obtain a synchrotron spectrum $F_{\nu } \propto \nu ^{-\alpha _{\nu }}$ , with the spect…