Search Publications
Broad-band high-energy emissions of the redback millisecond pulsar PSR J2129-0429
Kong, Albert K. H.; Zhao, J.; Hui, C. Y. +3 more
We present the first results from a joint XMM-Newton and NuSTAR observation of the gamma-ray emitting millisecond pulsar compact binary PSR J2129-0429. X-ray emission up to about 40 keV is detected and the joint spectrum can be modelled with a power-law plus a neutron star atmosphere model. At a distance of 1.4 kpc, the 0.3-79 keV luminosity is 3.…
Study of central light concentration in nearby galaxies
Ravikumar, C. D.; Aswathy, S.
We propose a novel technique to estimate the masses of supermassive black holes (SMBHs) residing at the centres of massive galaxies in the nearby Universe using simple photometry. Aperture photometry using SEXTRACTOR is employed to determine the central intensity ratio (CIR) at the optical centre of the galaxy image for a sample of 49 nearby galax…
Impact of quasar proper motions on the alignment between the International Celestial Reference Frame and the Gaia reference frame
Zhu, Z.; Liu, J. -C.; Malkin, Z.
The International Celestial Reference Frame (ICRF) is currently realized by the very long baseline interferometry (VLBI) observations of extragalactic sources with the zero proper motion assumption, while Gaia will observe proper motions of these distant and faint objects to an accuracy of tens of microarcseconds per year. This paper investigates …
The duration of reionization constrains the ionizing sources
Theuns, Tom; Frenk, Carlos; Sharma, Mahavir
We investigate how the nature of the galaxies that reionized the Universe affects the duration of reionization. We contrast two sets of models: one in which galaxies on the faint side of the luminosity function dominate the ionizing emissivity, and a second in which the galaxies on the bright side of the luminosity function dominate. The faint end…
Chromodynamical analysis of lenticular galaxies using globular clusters and planetary nebulae
Zanatta, Emilio J. B.; Cortesi, Arianna; Chies-Santos, Ana L. +7 more
Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics. we find the probability for a given…
Modelling dust rings in early-type galaxies through a sequence of radiative transfer simulations and 2D image fitting
Fritz, J.; Bonfini, P.; González-Martín, O. +3 more
A large fraction of early-type galaxies (ETGs) hosts prominent dust features, and central dust rings are arguably the most interesting among them. We present here `Lord of the Rings', a new methodology which allows to integrate the extinction by dust rings in a 2D-fittingmodelling of the surface brightness distribution. Our pipeline acts in two st…
Bayesian hierarchical modelling of initial-final mass relations acrossstar clusters
Si, Shijing; van Dyk, David A.; von Hippel, Ted +3 more
The initial-final mass relation (IFMR) of white dwarfs (WDs) plays an important role in stellar evolution. To derive precise estimates of IFMRs and explore how they may vary among star clusters, we propose a Bayesian hierarchical model that pools photometric data from multiple star clusters. After performing a simulation study to show the benefits…
Broadening of Ly α by neutral helium in DBA white dwarfs
Gänsicke, Boris T.; Toloza, Odette; Koester, Detlev +1 more
Traces of photospheric hydrogen are detected in at least half of all white dwarfs with helium-dominated atmospheres through the presence of H α in high-quality optical spectroscopy. Previous studies have noted significant discrepancies between the hydrogen abundances derived from H α and Ly α for a number of stars where ultraviolet spectroscopy is…
3D modelling of HCO+ and its isotopologues in the low-mass proto-star IRAS16293-2422
Caux, E.; Wakelam, V.; Bottinelli, S. +1 more
Ions and electrons play an important role in various stages of the star formation process. By following the magnetic field of their environment and interacting with neutral species, they slow down the gravitational collapse of the proto-star envelope. This process (known as ambipolar diffusion) depends on the ionization degree, which can be derive…
HST/WFPC2 imaging analysis and cloudy modelling of the multiple-shell planetary nebulae NGC 3242, NGC 6826, and NGC 7662
Kimeswenger, S.; Barría, D.
We performed a detailed photometric analysis and photoionization modelling on three high-excitation multiple-shell planetary nebulae: NGC 3242, NGC 6826, and NGC 7662. Archival Hubble Space Telescope/Wide Field Planetary Camera 2 (HST/WFPC2) narrow band filter images were used to investigate shocked regions by two independent methods: using low-ex…