4 research outputs found
Galaxy Collisions - Dawn of a New Era
The study of colliding galaxies has progressed rapidly in the last few years,
driven by observations with powerful new ground and space-based instruments.
These instruments have used for detailed studies of specific nearby systems,
statistical studies of large samples of relatively nearby systems, and
increasingly large samples of high redshift systems. Following a brief summary
of the historical context, this review attempts to integrate these studies to
address the following key issues. What role do collisions play in galaxy
evolution, and how can recently discovered processes like downsizing resolve
some apparently contradictory results of high redshift studies? What is the
role of environment in galaxy collisions? How is star formation and nuclear
activity orchestrated by the large scale dynamics, before and during merger?
Are novel modes of star formation involved? What are we to make of the
association of ultraluminous X-ray sources with colliding galaxies? To what do
degree do mergers and feedback trigger long-term secular effects? How far can
we push the archaeology of individual systems to determine the nature of
precursor systems and the precise effect of the interaction? Tentative answers
to many of these questions have been suggested, and the prospects for answering
most of them in the next few decades are good.Comment: 44 pages, 9 figures, review article in press for Astrophysics Update
Vol.
Low luminosity Type II supernovae - IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class
Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) 2020cxd and 2021aai are presented. SN 2020cxd was discovered 2 d after explosion at an absolute magnitude of M-r = -14.02 +/- 0.21 mag, subsequently settling on a plateau which lasts for similar to 120 d. Through the luminosity of the late light curve tail, we infer a synthesized Ni-56 mass of (1.8 +/- 0.5) x 10(-3) M-circle dot. During the early evolutionary phases, optical spectra show a blue continuum (T > 8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases, Ca II, Fe II, Sc II, and Ba II lines dominate the spectra. Hydrodynamical modelling of the observables yields R similar or equal to 575 R-circle dot for the progenitor star, with M-ej = 7.5 M-circle dot and E similar or equal to 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asymptotic giant branch star. SN 2021aai reaches a maximum luminosity of M-r = -16.57 +/- 0.23 mag (correcting for A(V) = 1.92 mag), at the end of its remarkably long plateau (similar to 140 d). The estimated Ni-56 mass is (1.4 +/- 0.5) x 10(-2) M-circle dot. The expansion velocities are compatible with those of other LL SNe IIP (few 10(3) km s(-1)). The physical parameters obtained through hydrodynamical modelling are R similar or equal to 575 R-circle dot, M-ej = 15.5 M-circle dot, and E = 0.4 foe. SN 2021aai is therefore interpreted as the explosion of an RSG, with properties that bridge the class of LL SNe IIP with standard SN IIP events.</p
Low luminosity Type II supernovae - IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class
Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) 2020cxd and 2021aai are presented. SN 2020cxd was discovered 2 d after explosion at an absolute magnitude of Mr = -14.02 ± 0.21 mag, subsequently settling on a plateau which lasts for âŒ120 d. Through the luminosity of the late light curve tail, we infer a synthesized 56Ni mass of (1.8 ± 0.5) Ă 10-3 Mâ. During the early evolutionary phases, optical spectra show a blue continuum (T >8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases, Ca ii, Fe ii, Sc ii, and Ba ii lines dominate the spectra. Hydrodynamical modelling of the observables yields R ~ 575 Râ for the progenitor star, with Mej = 7.5 Mâ and E ~ 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asymptotic giant branch star. SN 2021aai reaches a maximum luminosity of Mr = -16.57 ± 0.23 mag (correcting for AV = 1.92 mag), at the end of its remarkably long plateau (âŒ140 d). The estimated 56Ni mass is (1.4 ± 0.5) Ă 10-2 Mâ. The expansion velocities are compatible with those of other LL SNe IIP (few 103 km s-1). The physical parameters obtained through hydrodynamical modelling are R ~575 Râ, Mej = 15.5 Mâ, and E = 0.4 foe. SN 2021aai is therefore interpreted as the explosion of an RSG, with properties that bridge the class of LL SNe IIP with standard SN IIP events