Bulge

Galaxy-wide star formation can be quenched by a number of physical processes such as environmental effects (e.g., ram pressure stripping) and supernova feedback. Using numerical simulations, we here demonstrate that star formation can be severely suppressed in disk galaxies with their gas disks counter-rotating with respect to their stellar disks. This new mechanism of star formation suppression (or quenching) does not depend so strongly on model parameters of disk galaxies, such as bulge-to-disk- ratios and gas mass fractions. Such severe suppression of star formation is due largely to the suppression of the gas density enhancing mechanism i.e spiral arm formation in disk galaxies with counter-rotating gas. Our simulations also show that molecular hydrogen and dust can be rather slowly consumed by star formation in disk galaxies with counter-rotating gas disks (i.e., long gas depletion timescale). Based on these results, we suggest that spiral and S0 galaxies with counter-rotation ...

Introduction: The field of medicine and dentistry has been able to use stem cells and tissue engineering to regenerate damaged tissues. This article finds the progress, challengesand future prospects. Stem Cells: Cells that have the ability to differentiate into various body cells are called stem cells. They primarily divided into two categories: embryonic stem cells (ESCs) and adult stem cells (MSCs). Tissue Engineering:Functional tissue production by combining cells, scaffolds and signaling factors, in such a way that the scaffolds provide: a threedimensional substrate for cell growth. signaling factors cause: differentiation, cell proliferation, and guide path towardsneeded tissues. Empirical approaches:Isolation of stem cells, their cultivation, making a scaffold and culturing cell on it. Results:In tissue engineering, stem cells have a high ability to repair and regenerate tissues, including: cardiac muscle, spinal cord, dental pulp,gingiva, etc. Current limitations:Rejection by immunity, Improper ability in mastery in scaffold integration, ethical concerns (use of embryonic stem cells). Conclusion:Tissue engineering has advanced the medical and dental science by damaged tissue regeneration.Thoughthere are various challenges in this regard, butprogress is going ontofindbettersolutions.

Context. Globular clusters (GCs) are the oldest objects known in the Milky Way, so each discovery of a new GC is astrophysically important. In the inner Galactic bulge regions these objects are difficult to find due to extreme crowding and extinction. However, recent near-IR surveys have discovered a number of new bulge GC candidates that need to be further investigated. Aims. Our main objective is to use public data from the Gaia mission, the VISTA Variables in the Via Lactea (VVV) survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer to measure the physical parameters of Minni 48, a new candidate globular star cluster located in the inner bulge of the Milky Way at l = 359.35 deg, b = 2.79 deg. The specific goals are to measure its main astrophysical parameters, such as size, proper motions, metallicity, reddening and extinction, distance, total luminosity, and age. Methods. Even though there is a bright foreground star contaminating the field, this clu...

The central (‘bulge’) region of the Milky Way is teeming with a significant fraction of mildly metal-deficient stars with atmospheres that are strongly enriched in cyanogen (12C14N). Some of these objects, which are also known as nitrogen-enhanced stars, are hypothesised to be relics of the ancient assembly history of the Milky Way. Although the chemical similarity of nitrogen-enhanced stars to the unique chemical patterns observed in globular clusters has been observed, a direct connection between field stars and globular clusters has not yet been proven. In this work, we report on high-resolution, near-infrared spectroscopic observations of the bulge globular cluster NGC 6723, and the serendipitous discovery of a star, 2M18594405−3651518, located outside the cluster (near the tidal radius) but moving on a similar orbit, providing the first clear piece of evidence of a star that was very likely once a cluster member and has recently been ejected. Its nitrogen abundance ratio ([N/Fe...

Observations suggest that satellite quenching plays a major role in the build-up of passive, low-mass galaxies at late cosmic times. Studies of low-mass satellites, however, are limited by the ability to robustly characterize the local environment and star formation activity of faint systems. In an effort to overcome the limitations of existing data sets, we utilize deep photometry in Stripe 82 of the Sloan Digital Sky Survey, in conjunction with a neural network classification scheme, to study the suppression of star formation in low-mass satellite galaxies in the local Universe. Using a statistically driven approach, we are able to push beyond the limits of existing spectroscopic data sets, measuring the satellite quenched fraction down to satellite stellar masses of ∼10 7 M in group environments (M halo = 10 13−14 h −1 M). At high satellite stellar masses (10 10 M), our analysis successfully reproduces existing measurements of the quenched fraction based on spectroscopic samples. Pushing to lower masses, we find that the fraction of passive satellites increases, potentially signalling a change in the dominant quenching mechanism at M ∼ 10 9 M. Similar to the results of previous studies of the Local Group, this increase in the quenched fraction at low satellite masses may correspond to an increase in the efficacy of ram-pressure stripping as a quenching mechanism in groups.

Studies of the red clump giant population in the inner Milky Way suggest the Galactic bulge/bar has a boxy/peanut/X-shaped structure as predicted by its formation via a disc buckling instability. We used a non-parametric method of estimating the Galactic bulge morphology that is based on maximum entropy regularization. This enabled us to extract the 3D distribution of the red giant stars in the bulge from deep photometric catalogues of the VISTA Variables in the Via Lactea survey. Our high-resolution reconstruction confirms the well-known boxy/peanut/X-shaped structure of the bulge. We also find spiral arm structures that extend to around 3 kpc in front of and behind the bulge and are on different sides of the bulge major axis. We show that the detection of these structures is robust to the uncertainties in the luminosity function.

We explore a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in simulations that form boxy/peanut (b/p) bulges. The morphology of bars and b/p’s vary for different mono-abundance populations, according to their kinematic properties, which are in turn set by the galaxy’s assembly history. We find that the Auriga galaxies which best reproduce the chemo-kinematic properties of the Milky Way bulge have a negligible fraction of ex-situ stars in the b/p region (< 1%), with flattened, thick disc-like metal-poor stellar populations, and with their last major merger occurring at tlookback > 12 Gyrs. This imposes an upper limit on the stellar mass ratio of subsequent mergers, which we find is broadly consistent with the recently proposed Gaia Sausage/Enceladus merger. The average fraction of ex-situ stars in the central regions of Auriga galaxies that form b/p’s is 3% – significantly lower than in those which do not form bars or b/p’s. While these centra...

We explore the chemodynamical properties of a sample of barred galaxies in the Auriga magnetohydrodynamical cosmological zoom-in simulations, which form boxy/peanut (b/p) bulges, and compare these to the Milky Way (MW). We show that the Auriga galaxies which best reproduce the chemodynamical properties of stellar populations in the MW bulge have quiescent merger histories since redshift z ∼ 3.5: their last major merger occurs at $t_{\rm lookback}\gt 12\, \rm Gyr$, while subsequent mergers have a stellar mass ratio of ≤1:20, suggesting an upper limit of a few per cent for the mass ratio of the recently proposed Gaia Sausage/Enceladus merger. These Auriga MW-analogues have a negligible fraction of ex-situ stars in the b/p region ($\lt 1{{\ \rm per\ cent}}$), with flattened, thick disc-like metal-poor stellar populations. The average fraction of ex-situ stars in the central regions of all Auriga galaxies with b/p’s is 3 per cent – significantly lower than in those which do not host a b...

We study the galactic bulges in the Auriga simulations, a suite of 30 cosmological magneto-hydrodynamical zoom-in simulations of late-type galaxies in Milky Way sized dark matter haloes performed with the moving-mesh code arepo. We aim to characterize bulge formation mechanisms in this large suite of galaxies simulated at high resolution in a fully cosmological context. The bulges of the Auriga galaxies show a large variety in their shapes, sizes, and formation histories. According to observational classification criteria, such as Sérsic index and degree of ordered rotation, the majority of the Auriga bulges can be classified as pseudo-bulges, while some of them can be seen as composite bulges with a classical component; however, none can be classified as a classical bulge. Auriga bulges show mostly an in situ origin, $21{{\ \rm per\ cent}}$ of them with a negligible accreted fraction (facc < 0.01). In general, their in situ component was centrally formed, with ${\sim}75{{\ \rm p...