scholarly journals The effect of tides on the Sculptor dwarf spheroidal galaxy

2019 ◽  
Vol 487 (4) ◽  
pp. 5692-5710 ◽  
Author(s):  
G Iorio ◽  
C Nipoti ◽  
G Battaglia ◽  
A Sollima
Keyword(s):  
Milky Way ◽  
Ad Hoc ◽  
Stellar Kinematics ◽  
Data Set ◽  
Dwarf Spheroidal Galaxies ◽  
Massive Galaxies ◽  
Stellar Component ◽  
Recent Estimate ◽  
The Universe ◽  
Simulated Object

AbstractDwarf spheroidal galaxies (dSphs) appear to be some of the most dark matter (DM)-dominated objects in the Universe. Their dynamical masses are commonly derived using the kinematics of stars under the assumption of equilibrium. However, these objects are satellites of massive galaxies (e.g. the Milky Way) and thus can be influenced by their tidal fields. We investigate the implication of the assumption of equilibrium focusing on the Sculptor dSph by means of ad hoc N-body simulations tuned to reproduce the observed properties of Sculptor following the evolution along some observationally motivated orbits in the Milky Way gravitational field. For this purpose, we used state-of-the-art spectroscopic and photometric samples of Sculptor’s stars. We found that the stellar component of the simulated object is not directly influenced by the tidal field, while ${\approx } 30\!-\!60{{\ \rm per\ cent}}$ of the mass of the more diffuse DM halo is stripped. We conclude that, considering the most recent estimate of the Sculptor proper motion, the system is not affected by the tides and the stellar kinematics represents a robust tracer of the internal dynamics. In the simulations that match the observed properties of Sculptor, the present-day dark-to-luminous mass ratio is ≈6 within the stellar half-light radius (≈0.3 kpc) and >50 within the maximum radius of the analysed data set (≈1.5○, ≈2 kpc).

scholarly journals The Distribution Of Dark Mass In Galaxies

1996 ◽  
Vol 173 ◽  
pp. 165-174 ◽  
Author(s):  
Penny D. Sackett
Keyword(s):  
Dark Matter ◽  
Temperature Profile ◽  
Gravitational Lensing ◽  
Milky Way ◽  
Stellar Kinematics ◽  
X Ray ◽  
Neutral Gas ◽  
Complementary Techniques ◽  
Gas Layer ◽  
The Universe

Gravitational lensing is one of a number of methods used to probe the distribution of dark mass in the Universe. On galactic scales, complementary techniques include the use of stellar kinematics, the kinematics and morphology of the neutral gas layer, kinematics of satellites, and the morphology and temperature profile of X-ray halos. These methods are compared, with emphasis on their relative strengths and weaknesses in constraining the distribution and extent of dark matter in the Milky Way and other galaxies. It is concluded that (1) the extent of dark halos remains ill-constrained, (2) halos need not be isothermal, and (3) the dark mass is probably quite flattened.

scholarly journals The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis

2017 ◽  
Vol 608 ◽  
pp. A89 ◽  
Author(s):  
L. Mashonkina ◽  
P. Jablonka ◽  
T. Sitnova ◽  
Yu. Pakhomov ◽  
P. North
Keyword(s):  
Milky Way ◽  
Dwarf Galaxy ◽  
Chemical Species ◽  
Dwarf Spheroidal Galaxies ◽  
Massive Galaxies ◽  
Type Ia ◽  
Ursa Minor ◽  
R Process ◽  
Ia Supernovae ◽  
Process Elements

We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, −4 ≤ [Fe/H] ≾−2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo. Our results are based on high-resolution spectroscopic datasets and homogeneous and accurate atmospheric parameters determined in Paper I. We show that once the NLTE effects are properly taken into account, all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [α/Fe] ≃ 0.3 for each of the α-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in α/Fe with increasing metallicity in the Boötes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. We show that Sr in the massive galaxies is well correlated with Mg suggesting a strong link to massive stars and that its origin is essentially independent of Ba, for most of the [Ba/H] range. Our three UFDs, that is Boötes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg] ≃−1.3 and [Ba/Mg] ≃−1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of their neutron-capture elements. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H] <−2, is the strongest.

scholarly journals Why do extremely massive disc galaxies exist today?

2020 ◽  
Vol 494 (4) ◽  
pp. 5568-5575 ◽  
Author(s):  
R A Jackson ◽  
G Martin ◽  
S Kaviraj ◽  
C Laigle ◽  
J E G Devriendt ◽  
...  
Keyword(s):  
Mass Function ◽  
Stellar Mass ◽  
Morphological Transformation ◽  
Massive Galaxies ◽  
Stellar Component ◽  
Accretion Rates ◽  
Stellar Masses ◽  
Black Hole Masses ◽  
The Universe ◽  
Disc Galaxies

ABSTRACT Galaxy merger histories correlate strongly with stellar mass, largely regardless of morphology. Thus, at fixed stellar mass, spheroids and discs share similar assembly histories, both in terms of the frequency of mergers and the distribution of their mass ratios. Since mergers drive disc-to-spheroid morphological transformation, and the most massive galaxies typically have the richest merger histories, it is surprising that discs exist at all at the highest stellar masses (e.g. beyond the knee of the mass function). Using Horizon-AGN, a cosmological hydroynamical simulation, we show that extremely massive (M* &gt; 1011.4 M⊙) discs are created via two channels. In the primary channel (accounting for 70${\rm {per\ cent}}$ of these systems and 8${\rm {per\ cent}}$ of massive galaxies), the most recent, significant (mass ratio &gt; 1:10) merger between a massive spheroid and a gas-rich satellite ‘spins up’ the spheroid by creating a new rotational stellar component, leaving a massive disc as the remnant. In the secondary channel (accounting for 30 ${\rm {per\ cent}}$ of these systems and 3 ${\rm {per\ cent}}$ of massive galaxies), a system maintains a disc throughout its lifetime, due to an anomalously quiet merger history. Not unexpectedly, the fraction of massive discs increases towards higher redshift, due to the Universe being more gas-rich. The morphological mix of galaxies at the highest stellar masses is, therefore, a strong function of the gas fraction of the Universe. Finally, these massive discs have similar black hole masses and accretion rates to massive spheroids, providing a natural explanation for why some powerful AGN are surprisingly found in disc galaxies.

scholarly journals The Effect of Tidal Stripping on Composite Stellar Populations in Dwarf Spheroidal Galaxies

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Laura V. Sales ◽  
Amina Helmi ◽  
Giuseppina Battaglia
Keyword(s):  
Dark Matter ◽  
Mass Loss ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Local Group ◽  
Stellar Populations ◽  
Dwarf Spheroidal Galaxies ◽  
Stellar Component ◽  
Dwarf Spheroidals ◽  
Matter Component

We use N-body simulations to study the effects of tides on the kinematical structure of satellite galaxies orbiting a Milky Way-like potential. Here we focus on the evolution of a spherical, dark matter dominated satellite, which is modelled with two stellar components set ab initio to be spatially and kinematically segregated, in a way that resembles the configuration of the metal poor and metal rich stellar populations in several dwarf spheroidals of the Local Group. We find that an important attenuation of the initial differences in the distribution of the two stellar components occurs for orbits with small pericentric radii. This is mainly due to (i) the loss of the gravitational support provided by the dark matter component after tidal stripping takes place and (ii) tides preferentially affect the more extended stellar component, leading to a net decrease in its velocity dispersion as a response for the mass loss, which thus shrinks the kinematical gap. We apply these ideas to the Sculptor and Carina dwarf spheroidals. Differences in their orbits might help to explain why in the former a clear kinematical separation between metal poor and metal rich stars is apparent, while in Carina this segregation is significantly more subtle.

scholarly journals Simulations of satellite tidal debris in the Milky Way halo

2020 ◽  
Vol 636 ◽  
pp. A106
Author(s):  
Matteo Mazzarini ◽  
Andreas Just ◽  
Andrea V. Macciò ◽  
Reza Moetazedian
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Host Galaxy ◽  
Massive Galaxies ◽  
Stellar Component ◽  
Radial Profiles ◽  
Hydrodynamical Simulations ◽  
A Minor ◽  
Power Law Index ◽  
Milky Way Halo

Aims. We study the distribution of the stellar and dark matter debris of the Milky Way satellites. Methods. For the first time we address the question of the tidal disruption of satellites in simulations by utilising simultaneously (a) a realistic set of orbits extracted from cosmological simulations; (b) a three-component host galaxy with live halo, disc, and bulge components; and (c) satellites from hydrodynamical simulations. We analyse the statistical properties of the satellite debris of all massive galaxies reaching the inner Milky Way on a timescale of 2 Gyr. Results. Up to 80% of the dark matter is stripped from the satellites, while this happens for up to 30% of their stars. The stellar debris ends mostly in the inner Milky Way halo, whereas the dark matter debris shows a flat mass distribution over the full main halo. The dark matter debris follows a density profile with inner power law index αDM = −0.66 and outer index βDM = 2.94, while for stars α* = −0.44 and β* = 6.17. In the inner 25 kpc the distribution of the stellar debris is flatter than that of the dark matter debris, and the orientations of their short axes differ significantly. Changing the orientation of the stellar disc by 90° has a minor impact on the distribution of the satellite debris. Conclusions. Our results indicate that dark matter is more easily stripped than stars from the Milky Way satellites. The structure of the debris is dominated by the satellite orbital properties. The radial profiles, the flattening, and the orientation of the stellar and dark matter debris are significantly different, which prevents the prediction of the dark matter distribution from the observed stellar component.

The Long View of Planetary Systems

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Planetary Systems ◽  
Giant Planets ◽  
Milky Way Galaxy ◽  
Population Statistics ◽  
The Past ◽  
General Terms ◽  
The Galaxy ◽  
The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

scholarly journals Investigating the properties of a galaxy group at z = 0.6

2020 ◽  
Vol 15 (S359) ◽  
pp. 188-189
Author(s):  
Daniela Hiromi Okido ◽  
Cristina Furlanetto ◽  
Marina Trevisan ◽  
Mônica Tergolina
Keyword(s):  
Large Scale ◽  
The Other ◽  
Numerical Density ◽  
Spectroscopy Data ◽  
Stellar Kinematics ◽  
Galaxy Groups ◽  
The Galaxy ◽  
The Difference ◽  
The Impact ◽  
The Universe

AbstractGalaxy groups offer an important perspective on how the large-scale structure of the Universe has formed and evolved, being great laboratories to study the impact of the environment on the evolution of galaxies. We aim to investigate the properties of a galaxy group that is gravitationally lensing HELMS18, a submillimeter galaxy at z = 2.39. We obtained multi-object spectroscopy data using Gemini-GMOS to investigate the stellar kinematics of the central galaxies, determine its members and obtain the mass, radius and the numerical density profile of this group. Our final goal is to build a complete description of this galaxy group. In this work we present an analysis of its two central galaxies: one is an active galaxy with z = 0.59852 ± 0.00007, while the other is a passive galaxy with z = 0.6027 ± 0.0002. Furthermore, the difference between the redshifts obtained using emission and absorption lines indicates an outflow of gas with velocity v = 278.0 ± 34.3 km/s relative to the galaxy.

scholarly journals Estimating relatedness between malaria parasites

2019 ◽  
Author(s):  
Aimee R. Taylor ◽  
Pierre E. Jacob ◽  
Daniel E. Neafsey ◽  
Caroline O. Buckee
Keyword(s):  
Genetic Epidemiology ◽  
Ad Hoc ◽  
Pathogen Transmission ◽  
Identity By Descent ◽  
Malaria Parasites ◽  
Data Set ◽  
Epidemiology Studies ◽  
Diverse Data ◽  
Prospective Study Design ◽  
Identity By State

1.AbstractUnderstanding the relatedness of individuals within or between populations is a common goal in biology. Increasingly, relatedness features in genetic epidemiology studies of pathogens. These studies are relatively new compared to those in humans and other organisms, but are important for designing interventions and understanding pathogen transmission. Only recently have researchers begun to routinely apply relatedness to apicomplexan eukaryotic malaria parasites, and to date have used a range of different approaches on an ad hoc basis. It remains unclear how to compare different studies, therefore, and which measures to use. Here, we systematically compare measures based on identity-by-state and identity-by-descent using a globally diverse data set of malaria parasites,Plasmodium falciparumandPlasmodium vivax, and provide marker requirements for estimates based on identity-by-descent. We formally show that the informativeness of polyallelic markers for relatedness inference is maximised when alleles are equifrequent. Estimates based on identity-by-state are sensitive to allele frequencies, which vary across populations and by experimental design. For portability across studies, we thus recommend estimates based on identity-by-descent. To generate reliable estimates, we recommend approximately 200 biallelic or 100 polyallelic markers. Confidence intervals illuminate inference across studies based on different sets of markers. These marker requirements, unlike many thus far reported, are immediately applicable to haploid malaria parasites and other haploid eukaryotes. This is the first attempt to provide rigorous analysis of the reliability of, and requirements for, relatedness inference in malaria genetic epidemiology, and will provide a basis for statistically informed prospective study design and surveillance strategies.

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