Gaseous Halos of Simulated Milky Way-like Galaxies

In order to investigate the role of the host halo in quenching satellite galaxies, we have characterized a single Milky Way-like host galaxy from the FIRE simulations from z = 0–1.76 by quantifying the gas density of the host halo environment with respect to distance from the host and galactocentric latitude. The gas density decreases with increasing distance from the host according to a broken power law. At earlier times (2–10 Gyr ago), the density in the inner regions of the host halo was enhanced relative to z = 0. Thus, earlier infalling satellites experienced more ram-pressure and were more efficiently quenched compared to later infalling satellites. We also find that in the inner halo (<150 kpc) the density is 2–3 times larger close to the plane of the host galaxy disk versus above or below the disk, so satellites that orbit at low galactocentric latitudes may be more efficiently quenched.

Loud Noises Lead To Dementia

Dementia is an umbrella term for a collection of symptoms that are caused by disorders affecting the brain and impact on memory, thinking, behaviour and emotion. The most common is Alzheimer’s disease, which affects 50-60% of people with dementia. Other types of dementia include vascular dementia, Lewy body dementia and fronto-temporal dementia. Dementia can also sometimes affect people who are under the age of 65. This is known as young onset dementia. Our brains are made up of over 86 billion nerve cells – more than the stars in the Milky Way. Dementia damages nerve cells so they are no longer able to communicate effectively and this impacts on how our body functions.

The Milky Way Revealed by Variable Stars. I. Sample Selection of RR Lyrae Stars and Evidence for Merger History

In order to study the Milky Way, RR Lyrae (RRL) variable stars identified by Gaia, ASAS-SN, and ZTF sky survey projects have been analyzed as tracers in this work. Photometric and spectroscopic information of 3417 RRLs including proper motions, radial velocity, and metallcity are obtained from observational data of Gaia, LAMOST, GALAH, APOGEE, and RAVE. Precise distances of RRLs with typical uncertainties less than 3% are derived by using a recent comprehensive period–luminosity–metallicity relation. Our results from kinematical and chemical analysis provide important clues for the assembly history of the Milky Way, especially for the Gaia–Sausage ancient merger. The kinematical and chemical trends found in this work are consistent with those of recent simulations that indicated that the Gaia–Sausage merger had a dual origin in the Galactic thick disk and halo. As recent similar works have found, the halo RRL sample in this work contains a subset of radially biased orbits besides a more isotropic component. This higher orbital anisotropy component amounts to β ≃ 0.8, and it contributes between 42% and 83% of the halo RRLs at 4 < R( kpc) < 20.

The Warm Gas in the Milky Way: The Kinematical Model of C iv and Its Connection to Si iv

We compose a 265-sight-line Milky Way C iv line-shape sample using the Hubble Space Telescope/Cosmic Origins Spectrograph archive, which is complementary to the existing Si iv samples. C iv has a higher ionization potential (47–64 eV) than Si iv (33–45 eV), so it also traces warm gas, which is roughly cospatial with Si iv. The spatial density distribution and kinematics of C iv are identical to those Si iv within ≈2σ. C iv is more sensitive to the warm gas density distribution at large radii with a higher element abundance. Applying the kinematical model to the C iv sample, we find two possible solutions of the density distribution, which are distinguished by the relative extension along the disk midplane and the normal-line direction. Both solutions can reproduce the existing sample and suggest a warm gas disk mass of log M ( M ⊙ ) ≈ 8 and an upper limit of log M ( M ⊙ ) < 9.3 within 250 kpc, which is consistent with Si iv. There is a decrease in the C iv/Si iv column density ratio from the Galactic center to the outskirts by 0.2–0.3 dex, which may suggest a phase transition or different ionization mechanisms for C iv and Si iv. Also, we find that the difference between C iv and Si iv is an excellent tracer of small-scale features, and we find a typical size of 5°–10° for possible turbulence within individual clouds (≈1 kpc).

Simulating Globular Clusters in Dark Matter Subhalos

A cosmological zoom-in simulation that develops into a Milky Way-like halo begins at redshift 7. The initial dark matter distribution is seeded with dense star clusters of median mass 5 × 105 M ⊙, placed in the largest subhalos present, which have a median peak circular velocity of 25 km s−1. Three simulations are initialized using the same dark matter distribution with the star clusters starting on approximately circular orbits having initial median radii 6.8, 0.14 kpc, and, at the exact center of the subhalos. The simulations are evolved to the current epoch at which time the median galactic orbital radii of the three sets of clusters are 30, 5, and 16 kpc, with the clusters losing about 2%, 50%, and 15% of their mass, respectively. Clusters beginning at small orbital radii have so much tidal forcing that they are often not in equilibrium. Clusters that start at larger subhalo radii have a velocity dispersion that declines smoothly to ≃20% of the central value at ≃20 half-mass radii. The clusters that begin in the subhalo centers can show a rise in velocity dispersion beyond 3–5 half-mass radii. That is, the clusters that form without local dark matter always have stellar-mass-dominated kinematics at all radii, whereas about 25% of the clusters that begin in subhalo centers have remnant local dark matter.

The Mass of the Central Region of the Milky way Galaxy

On the Basis of tabular values of the gravitational constant. The calculated mass of the Nucleus of the Milky Way galaxy. The numerical value of the gravitational constant is determined by the mass of the nucleus of the milky way galaxy

Kinematics of the Milky Way Thick disk in solar neighborhood

Using GAIA EDR3 catalog, we present the detailed analysis of the two-component Milky Way stellar disk in the solar neighborhood. To determine the kinematical properties of the thin and of the Thick disks, we select the complete sample of about 278,000 evolved red giant branch (RGB) stars distributed in the cylinder of 1 kpc radius and 0.5 kpc height centered at the Sun. We measured the following mean velocities and dispersions for the thin and the Thick disks, respectively: [Formula: see text][Formula: see text]km s[Formula: see text] with [Formula: see text][Formula: see text]km s[Formula: see text], and [Formula: see text][Formula: see text]km s[Formula: see text] with [Formula: see text][Formula: see text]km s[Formula: see text]. Errors in mean velocities and dispersions are all less than 1[Formula: see text]km s[Formula: see text]. Same values were computed on much smaller subsamples of our Gaia data with RAVE DR5 [Fe/H] values, from which a metallicity selection was added. Results are basically the same. We find that up to 500 pc height above/below the galactic plane, Thick disk stars comprise about half the stars of the disk. We also find evidence of a substructure in [Formula: see text] versus [Formula: see text] in the thick disk population mostly that would give support to the accretion scenario for the formation of the thick disk.