scholarly journals Unexpected LIGO events and the mirror world

2021 ◽  
Vol 503 (2) ◽  
pp. 2882-2886
Author(s):  
Revaz Beradze ◽  
Merab Gogberashvili
Keyword(s):  
Star Formation ◽  
Matter Density ◽  
Lower Mass ◽  
Ordinary Matter ◽  
Star Evolution ◽  
Order Of Magnitude

ABSTRACT We consider the possibility that LIGO events GW190521, GW190425, and GW190814 may have emerged from the mirror world binaries. Theories of star evolution predict so-called upper and lower mass gaps and masses of these merger components lie in that gaps. In order to explain these challenging events very specific assumptions are required and we argue that such scenarios are order of magnitude more probable in mirror world, where star formation begins earlier and matter density can exceed five times the ordinary matter density.

scholarly journals Is there enough star formation in simulated protoclusters?

2020 ◽  
Vol 501 (2) ◽  
pp. 1803-1822
Author(s):  
Seunghwan Lim ◽  
Douglas Scott ◽  
Arif Babul ◽  
David J Barnes ◽  
Scott T Kay ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Star Formation History ◽  
Test Case ◽  
Numerical Resolution ◽  
Formation History ◽  
Order Of Magnitude ◽  
History Of ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT As progenitors of the most massive objects, protoclusters are key to tracing the evolution and star formation history of the Universe, and are responsible for ${\gtrsim }\, 20$ per cent of the cosmic star formation at $z\, {\gt }\, 2$. Using a combination of state-of-the-art hydrodynamical simulations and empirical models, we show that current galaxy formation models do not produce enough star formation in protoclusters to match observations. We find that the star formation rates (SFRs) predicted from the models are an order of magnitude lower than what is seen in observations, despite the relatively good agreement found for their mass-accretion histories, specifically that they lie on an evolutionary path to become Coma-like clusters at $z\, {\simeq }\, 0$. Using a well-studied protocluster core at $z\, {=}\, 4.3$ as a test case, we find that star formation efficiency of protocluster galaxies is higher than predicted by the models. We show that a large part of the discrepancy can be attributed to a dependence of SFR on the numerical resolution of the simulations, with a roughly factor of 3 drop in SFR when the spatial resolution decreases by a factor of 4. We also present predictions up to $z\, {\simeq }\, 7$. Compared to lower redshifts, we find that centrals (the most massive member galaxies) are more distinct from the other galaxies, while protocluster galaxies are less distinct from field galaxies. All these results suggest that, as a rare and extreme population at high z, protoclusters can help constrain galaxy formation models tuned to match the average population at $z\, {\simeq }\, 0$.

scholarly journals A new distance to the Brick, the dense molecular cloud G0.253+0.016

2021 ◽  
Vol 502 (1) ◽  
pp. 1246-1252
Author(s):  
M Zoccali ◽  
E Valenti ◽  
F Surot ◽  
O A Gonzalez ◽  
A Renzini ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Near Infrared ◽  
Formation Rate ◽  
Dynamical Evolution ◽  
Galactic Centre ◽  
The Galaxy ◽  
Centre Region ◽  
Order Of Magnitude ◽  
Red Clump

ABSTRACT We analyse the near-infrared colour–magnitude diagram of a field including the giant molecular cloud G0.253+0.016 (a.k.a. The Brick) observed at high spatial resolution, with HAWK-I@VLT. The distribution of red clump stars in a line of sight crossing the cloud, compared with that in a direction just beside it, and not crossing it, allow us to measure the distance of the cloud from the Sun to be 7.20, with a statistical uncertainty of ±0.16 and a systematic error of ±0.20 kpc. This is significantly closer than what is generally assumed, i.e. that the cloud belongs to the near side of the central molecular zone, at 60 pc from the Galactic centre. This assumption was based on dynamical models of the central molecular zone, observationally constrained uniquely by the radial velocity of this and other clouds. Determining the true position of the Brick cloud is relevant because this is the densest cloud of the Galaxy not showing any ongoing star formation. This puts the cloud off by one order of magnitude from the Kennicutt–Schmidt relation between the density of the dense gas and the star formation rate. Several explanations have been proposed for this absence of star formation, most of them based on the dynamical evolution of this and other clouds, within the Galactic centre region. Our result emphasizes the need to include constraints coming from stellar observations in the interpretation of our Galaxy’s central molecular zone.

scholarly journals Central Molecular Zone of the Milky Way: Star Formation in an extreme Environment

2015 ◽  
Vol 11 (S315) ◽  
pp. 163-166
Author(s):  
Jens Kauffmann
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Spatial Scales ◽  
Extreme Environment ◽  
Average Density ◽  
High Mass ◽  
Density Structure ◽  
Star Formation Activity ◽  
Order Of Magnitude ◽  
Sgr A

AbstractThe Central Molecular Zone (CMZ; inner ~100 pc) hosts some of the most dense and massive molecular clouds of the Milky Way. These clouds might serve as local templates for dense clouds seen in nearby starburst galaxies or in the early universe. The clouds have a striking feature: they form stars at a very slow pace, considering their mass and high average density. Here we use interferometer data from ALMA and the SMA to show that this slow star formation is a consequence of the cloud density structure: CMZ clouds have a very flat density structure. They might, for example, exceed the average density of the Orion A molecular cloud by an order of magnitude on spatial scales ~5 pc, but CMZ “cores” of ~0.1 pc radius have masses and densities lower than what is found in the Orion KL region. This absence of highest–density gas probably explains the suppression of star formation. The clouds are relatively turbulent, and ALMA observations of H2CO and SiO indicate that the turbulence is induced by high–velocity shocks. We speculate that these shocks might prevent the formation of high–mass cores. It has been argued that the state of CMZ clouds depends on their position along the orbit around Sgr A*. Our incomplete data indicate no evolution in the density structure, and only a modest evolution in star formation activity per unit mass.

scholarly journals Dependence of gravitational wave transient rates on cosmic star formation and metallicity evolution history

2020 ◽  
Vol 493 (1) ◽  
pp. L6-L10 ◽  
Author(s):  
Petra N Tang ◽  
J J Eldridge ◽  
Elizabeth R Stanway ◽  
J C Bray
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Formation Rate ◽  
Compact Objects ◽  
Star Formation History ◽  
Compact Binary ◽  
Formation History ◽  
Order Of Magnitude ◽  
History Of

ABSTRACT We compare the impacts of uncertainties in both binary population synthesis models and the cosmic star formation history on the predicted rates of gravitational wave (GW) compact binary merger events. These uncertainties cause the predicted rates of GW events to vary by up to an order of magnitude. Varying the volume-averaged star formation rate density history of the Universe causes the weakest change to our predictions, while varying the metallicity evolution has the strongest effect. Double neutron star merger rates are more sensitive to assumed neutron star kick velocity than the cosmic star formation history. Varying certain parameters affects merger rates in different ways depending on the mass of the merging compact objects; thus some of the degeneracy may be broken by looking at all the event rates rather than restricting ourselves to one class of mergers.

scholarly journals DDO68-V1: an extremely metal-poor LBV in a void galaxy

2018 ◽  
Vol 14 (S344) ◽  
pp. 392-395
Author(s):  
Yulia Perepelitsyna ◽  
Simon Pustilnik
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Rare Event ◽  
Local Universe ◽  
Hii Region ◽  
V Band ◽  
Star Evolution ◽  
Low Metallicity ◽  
Massive Star Evolution

AbstractThe lowest metallicity massive stars in the Local Universe with $Z\sim \left( {{Z}_{\odot }}/50-{{Z}_{\odot }}/30 \right)$ are the crucial objects to test the validity of assumptions in the modern models of very low-metallicity massive star evolution. These models, in turn, have major implications for our understanding of galaxy and massive star formation in the early epochs. DDO68-V1 in a void galaxy DDO68 is a unique extremely metal-poor massive star. Discovered by us in 2008 in the HII region Knot3 with $Z={{Z}_{\odot }}/35\,\left[ 12+\log \left( \text{O/H} \right)\sim 7.14 \right]$, DDO68-V1 was identified as an LBV star. We present here the LBV lightcurve in V band, combining own new data and the last archive and/or literature data on the light of Knot3 over the 30 years. We find that during the years 2008-2011 the LBV have experienced a very rare event of ‘giant eruption’ with V-band amplitude of 4.5 mag ($V\sim {{24.5}^{m}}-{{20}^{m}}$).

scholarly journals The sensitivity of presupernova neutrinos to stellar evolution models

2020 ◽  
Vol 496 (3) ◽  
pp. 3961-3972
Author(s):  
Chinami Kato ◽  
Ryosuke Hirai ◽  
Hiroki Nagakura
Keyword(s):  
Time Evolution ◽  
Stellar Evolution ◽  
Phenomenological Model ◽  
Matter Density ◽  
Neutrino Emission ◽  
Central Density ◽  
Order Of Magnitude ◽  
Neutrino Luminosity

ABSTRACT We examine the sensitivity of neutrino emission to stellar evolution models for a 15 M⊙ progenitor, paying particular attention to a phase prior to the collapse. We demonstrate that the number luminosities in both electron-type neutrinos (νe) and their antipartners ($\bar{\nu }_\mathrm{ e}$) differ by more than an order of magnitude by changing spatial resolutions and nuclear network sizes on stellar evolution models. We also develop a phenomenological model to capture the essential trend of the diversity, in which neutrino luminosities are expressed as a function of central density, temperature, and electron fraction. In the analysis, we show that the neutrino luminosity can be well characterized by these central quantities. This analysis also reveals that the most influential quantity to the time evolution of νe luminosity is matter density, while it is temperature for $\bar{\nu }_\mathrm{ e}$. These qualitative trends will be useful and applicable to constrain the physical states of progenitors at the final stages of stellar evolution from future neutrino observations, although more detailed systematic studies including various mass progenitors are required to assess the applicability.

scholarly journals SDSS-IV MaNGA: the indispensable role of bars in enhancing the central star formation of low-z galaxies

2020 ◽  
Vol 499 (1) ◽  
pp. 1406-1423 ◽  
Author(s):  
Lin Lin ◽  
Cheng Li ◽  
Cheng Du ◽  
Enci Wang ◽  
Ting Xiao ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Local Environment ◽  
Central Star ◽  
Barred Galaxies ◽  
Secular Evolution ◽  
Integral Field Spectroscopy ◽  
Radial Profiles ◽  
Order Of Magnitude

ABSTRACT We analyse two-dimensional maps and radial profiles of EW(Hα), EW(HδA), and Dn(4000) of low-redshift galaxies using integral field spectroscopy from the MaNGA survey. Out of ≈1400 nearly face-on late-type galaxies with a redshift z < 0.05, we identify 121 “turnover” galaxies that each have a central upturn in EW(Hα), EW(HδA), and/or a central drop in Dn(4000), indicative of ongoing/recent star formation. The turnover features are found mostly in galaxies with a stellar mass above ∼1010 M⊙ and NUV – r colour less than ≈5. The majority of the turnover galaxies are barred, with a bar fraction of 89 ± 3 per cent. Furthermore, for barred galaxies, the radius of the central turnover region is found to tightly correlate with one-third of the bar length. Comparing the observed and the inward extrapolated star formation rate surface density, we estimate that the central SFR have been enhanced by an order of magnitude. Conversely, only half of the barred galaxies in our sample have a central turnover feature, implying that the presence of a bar is not sufficient to lead to a central SF enhancement. We further examined the SF enhancement in paired galaxies, as well as the local environment, finding no relation. This implies that the environment is not a driving factor for central SF enhancement in our sample. Our results reinforce both previous findings and theoretical expectation that galactic bars play a crucial role in the secular evolution of galaxies by driving gas inflow and enhancing the star formation and bulge growth in the centre.

scholarly journals X-ray signatures of black hole feedback: hot galactic atmospheres in IllustrisTNG and X-ray observations

2020 ◽  
Vol 494 (1) ◽  
pp. 549-570 ◽  
Author(s):  
Nhut Truong ◽  
Annalisa Pillepich ◽  
Norbert Werner ◽  
Dylan Nelson ◽  
Kiran Lakhchaura ◽  
...  
Keyword(s):  
State Of The Art ◽  
Quenching Mechanism ◽  
Lower Mass ◽  
Cosmological Simulations ◽  
X Ray ◽  
Star Forming ◽  
Magnitude Range ◽  
Order Of Magnitude ◽  
Quenching Mechanisms ◽  
Gaseous Atmospheres

ABSTRACT Hot gaseous atmospheres that permeate galaxies and extend far beyond their stellar distribution, where they are commonly referred to as the circumgalactic medium, imprint important information about feedback processes powered by the stellar populations of galaxies and their central supermassive black holes (SMBHs). In this work, we study the properties of this hot X-ray emitting medium using the IllustrisTNG cosmological simulations. We analyse their mock X-ray spectra, obtained from the diffuse and metal-enriched gas in TNG100 and TNG50, and compare the results with X-ray observations of nearby early-type galaxies. The simulations reproduce the observed X-ray luminosities (LX) and temperature (TX) at small (<Re) and intermediate (<5Re) radii reasonably well. We find that the X-ray properties of lower mass galaxies depend on their star formation rates. In particular, in the magnitude range where the star-forming and quenched populations overlap, $M_{\rm K}\sim -24\ (M_*\sim 10^{10.7}\, \mathrm{M}_\odot)$, we find that the X-ray luminosities of star-forming galaxies are on average about an order of magnitude higher than those of their quenched counterparts. We show that this diversity in LX is a direct manifestation of the quenching mechanism in the simulations, where the galaxies are quenched due to gas expulsion driven by SMBH kinetic feedback. The observed dichotomy in LX is thus an important observable prediction for the SMBH feedback-based quenching mechanisms implemented in state-of-the-art cosmological simulations. While the current X-ray observations of star-forming galaxies are broadly consistent with the predictions of the simulations, the observed samples are small and more decisive tests are expected from the sensitive all-sky X-ray survey with eROSITA.

scholarly journals The locations of SNe Ib/c and their comparison to those of WR stars and GRBs

2011 ◽  
Vol 7 (S279) ◽  
pp. 191-198
Author(s):  
Giorgos Leloudas
Keyword(s):  
Star Formation ◽  
Spectroscopic Study ◽  
Massive Stars ◽  
Lower Mass ◽  
The Difference ◽  
The One

AbstractThe locations of long GRBs and stripped supernovae are compared to those of their favored progenitors, WR stars, and their sub-classes. Compared to Leloudas et al. (2010), we have doubled the number of galaxies with suitable WR data. In the combined sample, WC stars are found, on average, in brighter locations than WN stars. The WN distribution is fully consistent with the one of SNe Ib, while it is inconsistent with those of SNe II, Ic and GRBs. The WC distribution is both consistent with SNe Ib and Ic. It is inconsistent with SNe II, and marginally consistent with GRBs. Furthermore, we present a spectroscopic study of the locations of SNe Ib/c. The average metallicity in the environments of SNe Ic is found to be a little higher than for SNe Ib, but the difference is small and not significant within our sample. Under the assumption that the SN regions were formed in an instantaneous burst of star formation, we find that a fraction of them appear older than what is allowed in order to host SNe Ib/c from single massive stars. Within this framework, these SNe must come from lower mass binaries.

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