Dwarf galaxy satellite systems are essential probes to test models of structure formation, making it necessary to establish a census of dwarf galaxies outside of our own Local Group. We present deep ...FORS2 VI band images from the ESO Very Large Telescope (VLT) for 15 dwarf galaxy candidates in the Centaurus group of galaxies. We confirm nine dwarfs to be members of Cen A by measuring their distances using a Bayesian approach to determine the tip of the red giant branch luminosity. We have also fit theoretical isochrones to measure their mean metallicities. The properties of the new dwarfs are similar to those in the Local Group in terms of their sizes, luminosities, and mean metallicities. Within our photometric precision, there is no evidence of a metallicity spread, but we do observe possible extended star formation in several galaxies, as evidenced by a population of asymptotic giant branch stars brighter than the red giant branch tip. The new dwarfs do not show any signs of tidal disruption. Together with the recently reported dwarf galaxies by the complementary PISCeS survey, we study the luminosity function and 3D structure of the group. By comparing the observed luminosity function to the high-resolution cosmological simulation IllustrisTNG, we find agreement within a 90% confidence interval. However, Cen A seems to be missing its brightest satellites and has an overabundance of the faintest dwarfs in comparison to its simulated analogs. In terms of the overall 3D distribution of the observed satellites, we find that the whole structure is flattened along the line-of-sight, with a root-mean-square (rms) height of 130 kpc and an rms semi-major axis length of 330 kpc. Future distance measurements of the remaining dwarf galaxy candidates are needed to complete the census of dwarf galaxies in the Centaurus group.
Elderly patients were randomly assigned to CABG with cardiopulmonary bypass (on-pump CABG) or without it (off-pump CABG). At 30 days and at 1 year, there was no significant difference in the ...composite outcome of death, stroke, MI, repeat revascularization, or new renal-replacement therapy.
There is an ongoing debate about the benefits and shortcomings of coronary-artery bypass grafting (CABG) without cardiopulmonary bypass (off-pump CABG). Cardiopulmonary bypass can have detrimental effects.
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Initial trials have shown that off-pump CABG is feasible in selected low-risk patients and offers results similar to those of CABG performed with the conventional on-pump technique (on-pump CABG). In institutions with experience in off-pump CABG, the rate of major adverse events and the rates of complete revascularization and graft patency have been similar to those with on-pump CABG.
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These positive results have been called into question by reports of inferior graft . . .
We present a photometric study of the dwarf galaxy population in the core region ( rvir/4) of the Fornax galaxy cluster based on deep u′g′i′ photometry from the Next Generation Fornax Cluster Survey. ...All imaging data were obtained with the Dark Energy Camera mounted on the 4 m Blanco telescope at the Cerro Tololo Interamerican Observatory. We identify 258 dwarf galaxy candidates with luminosities −17 Mg′ −8 mag, corresponding to typical stellar masses of , reaching ∼3 mag deeper in point-source luminosity and ∼4 mag deeper in surface brightness sensitivity compared to the classic Fornax Cluster Catalog. Morphological analysis shows that the dwarf galaxy surface-brightness profiles are well represented by single-component Sérsic models with average Sérsic indices of and average effective radii of . Color-magnitude relations indicate a flattening of the galaxy red sequence at faint galaxy luminosities, similar to the one recently discovered in the Virgo cluster. A comparison with population synthesis models and the galaxy mass-metallicity relation reveals that the average faint dwarf galaxy is likely older than ∼5 Gyr. We study galaxy scaling relations between stellar mass, effective radius, and stellar mass surface density over a stellar mass range covering six orders of magnitude. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be identified: (1) dwarf galaxies assemble mass inside the half-mass radius up to , (2) isometric mass assembly occurs in the range , and (3) massive galaxies assemble stellar mass predominantly in their halos at and above.
We present the detection of supermassive black holes (BHs) in two Virgo ultracompact dwarf galaxies (UCDs), VUCD3 and M59cO. We use adaptive optics assisted data from the Gemini/NIFS instrument to ...derive radial velocity dispersion profiles for both objects. Mass models for the two UCDs are created using multi-band Hubble Space Telescope imaging, including the modeling of mild color gradients seen in both objects. We then find a best-fit stellar mass-to-light ratio (M/L) and BH mass by combining the kinematic data and the deprojected stellar mass profile using Jeans Anisotropic Models. Assuming axisymmetric isotropic Jeans models, we detect BHs in both objects with masses of 4.4 − 3.0 + 2.5 × 10 6 M in VUCD3 and 5.8 − 2.8 + 2.5 × 10 6 M in M59cO (3 uncertainties). The BH mass is degenerate with the anisotropy parameter, β z ; for the data to be consistent with no BH requires β z = 0.4 and β z = 0.6 for VUCD3 and M59cO, respectively. Comparing these values with nuclear star clusters shows that, while it is possible that these UCDs are highly radially anisotropic, it seems unlikely. These detections constitute the second and third UCDs known to host supermassive BHs. They both have a high fraction of their total mass in their BH; ∼13% for VUCD3 and ∼18% for M59cO. They also have low best-fit stellar M/Ls, supporting the proposed scenario that most massive UCDs host high-mass fraction BHs. The properties of the BHs and UCDs are consistent with both objects being the tidally stripped remnants of ∼ 10 9 M galaxies.
Abstract The presence of dense, neutral hydrogen clouds in the hot, diffuse intragroup and intracluster (IC) medium is an important clue to the physical processes controlling the survival of cold gas ...and sheds light on cosmological baryon flows in massive halos. Advances in numerical modeling and observational surveys mean that theory and observational comparisons are now possible. In this paper, we use the high-resolution TNG50 cosmological simulation to study the H i distribution in seven halos with masses similar to the Fornax galaxy cluster. Adopting observational sensitivities similar to the MeerKAT Fornax Survey (MFS), an ongoing H i survey that will probe to column densities of 10 18 cm −2 , we find that Fornax-like TNG50 halos have an extended distribution of neutral hydrogen clouds. Within 1 R vir , we predict the MFS will observe a total H i covering fraction of ∼12% (mean value) for 10 kpc pixels and 6% for 2 kpc pixels. If we restrict this to gas more than 10 half-mass radii from galaxies, the mean values only decrease mildly, to 10% (4%) for 10 (2) kpc pixels (albeit with significant halo-to-halo spread). Although there are large amounts of H i outside of galaxies, the gas seems to be associated with satellites, judging both by the visual inspection of projections and by comparison of the line of sight velocities of galaxies and IC H i .
Background An exploratory analysis of the German Off Pump Coronary Artery Bypass Grafting in Elderly Patients (GOPCABE) trial was performed to investigate the effect of off-pump coronary artery ...bypass grafting (CABG) on kidney function after the operation. Methods Data on kidney function were available from 1,612 patients, representing 67% of the study population. Preoperative kidney function was graded according to the glomerular filtration rate. Acute kidney injury (AKI) within the first week after the operation was defined and classified according to the Acute Kidney Injury Network (AKIN) criteria. The incidence and severity of AKI was compared between patients operated on on-pump or off-pump. Results Impaired kidney function was seen in 642 patients (40%), and 19 patients had preexisting end-stage kidney disease. AKI of any severity occurred in half of all patients undergoing CABG, with AKIN stage 1 accounting for most of the cases. The incidence and severity of AKI in patients undergoing on-pump vs off-pump CABG was AKIN stage 1: 298 (37%) vs 329 (42%); AKIN stage 2: 38 (5%) vs 43 (5%); and AKIN stage 3: 44 (6%) vs 44 (6%), which did not differ significantly ( p = 0.174). New renal replacement therapy was necessary in 3.2% (on-pump) and in 2.7% (off-pump) of all patients. Stratification according to preoperative kidney function yielded comparable frequencies of AKI for on-pump and off-pump CABG. Conclusions AKI was common in elderly patients undergoing CABG, but deterioration of kidney function requiring renal replacement therapy was a rare event. Off-pump CABG was not associated with decreased rates or reduced severity of AKI in elderly patients.
We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive-optics-assisted near-IR integral field spectroscopy from Gemini/NIFS and Hubble ...Space Telescope (HST) imaging. We use the multiband HST imaging to create a mass model that suggests and accounts for the presence of multiple stellar populations and structural components. We combine these mass models with kinematics measurements from Gemini/NIFS to find a best-fit stellar mass-to-light ratio (M/L) and black hole (BH) mass using Jeans anisotropic models (JAMs), axisymmetric Schwarzschild models, and triaxial Schwarzschild models. The best-fit parameters in the JAM and axisymmetric Schwarzschild models have BHs between 2.5 and 5.9 million solar masses. The triaxial Schwarzschild models point toward a similar BH mass but show a minimum χ2 at a BH mass of ∼0. Models with a BH in all three techniques provide better fits to the central Vrms profiles, and thus we estimate the BH mass to be 4.2 − 1.7 + 2.1 × 10 6 M (estimated 1 uncertainties). We also present deep radio imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass measurements, and we compare these to X-ray measurements to check for consistency with the fundamental plane of BH accretion. We detect faint radio emission in M59cO but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray detections in both these sources. The BH mass and nuclear light profile of M59-UCD3 suggest that it is the tidally stripped remnant of a ∼109-1010 M galaxy.
The recent discovery of massive black holes (BHs) in the centers of high-mass ultra-compact dwarf galaxies (UCDs) suggests that at least some are the stripped nuclear star clusters of dwarf galaxies. ...We present the first study that investigates whether such massive BHs, and therefore stripped nuclei, also exist in low-mass (M < 107 M ) UCDs. We constrain the BH masses of two UCDs located in Centaurus A (UCD 320 and UCD 330) using Jeans modeling of the resolved stellar kinematics from adaptive optics data obtained with the SINFONI integral field spectrograph at the Very Large Telescope (VLT/SINFONI). No massive BHs are found in either UCD. We find a 3 upper limit on the central BH mass in UCD 330 of M < 1.0 × 105 M , which corresponds to 1.7% of the total mass. This excludes a high-mass fraction BH and would only allow low-mass BHs similar to those claimed to be detected in Local Group globular clusters. For UCD 320, poorer data quality results in a less constraining 3 upper limit of M < 1 × 106 M , which is equal to 37.7% of the total mass. The dynamical mass-to-light ratios of UCD 320 and UCD 330 are not inflated compared to predictions from stellar population models. The non-detection of BHs in these low-mass UCDs is consistent with the idea that elevated dynamical mass-to-light ratios do indicate the presence of a substantial BH. Although no massive BHs are detected, these systems could still be stripped nuclei. The strong rotation (v/ of 0.3-0.4) in both UCDs and the two-component light profile in UCD 330 support the idea that these UCDs may be stripped nuclei of low-mass galaxies whose BH occupation fraction is not yet known.
The VEGAS imaging survey of the Hydra I cluster has revealed an extended network of stellar filaments to the south-west of the spiral galaxy NGC 3314A. Within these filaments, at a projected distance ...of ∼40 kpc from the galaxy, we discover an ultra-diffuse galaxy (UDG) with a central surface brightness of
μ
0,
g
∼ 26 mag arcsec
−2
and effective radius
R
e
∼ 3.8 kpc. This UDG, named UDG 32, is one of the faintest and most diffuse low-surface-brightness galaxies in the Hydra I cluster. Based on the available data, we cannot exclude that this object is just seen in projection on top of the stellar filaments and is thus instead a foreground or background UDG in the cluster. However, the clear spatial coincidence of UDG 32 with the stellar filaments of NGC 3314A suggests that it might have formed from the material in the filaments, becoming a detached, gravitationally bound system. In this scenario, the origin of UDG 32 depends on the nature of the stellar filaments in NGC 3314A, which is still unknown. The stellar filaments could result from ram-pressure stripping or have a tidal origin. In this letter we focus on the comparison of the observed properties of the stellar filaments and of UDG 32 and speculate on their possible origin. The relatively red colour (
g
−
r
= 0.54 ± 0.14 mag) of the UDG, similar to that of the disk in NGC 3314A, combined with an age older than 1 Gyr and the possible presence of a few compact stellar systems, points towards a tidal formation scenario.
The origin of ultracompact dwarf (UCD) galaxies, compact extragalactic stellar systems, is still a puzzle for present galaxy formation models. We present the comprehensive analysis of high-resolution ...multi-object spectroscopic data for a sample of 24 Fornax cluster UCDs obtained with VLT with Fibre Large Array Multi Element Spectrograph (FLAMES). It comprises previously published data for 19 objects which we re-analysed, including 13 with available Hubble Space Telescope (HST) photometric data. Using Virtual Observatory technologies we found archival HST images for two more UCDs and then determined their structural properties. For all objects we derived internal velocity dispersions, stellar population parameters and stellar mass-to-light ratios (M/L)* by fitting individual simple stellar population (SSP) synthetic spectra convolved with a Gaussian against the observed spectra using the NBursts full spectral fitting technique. For 14 objects we estimated dynamical masses suggesting no dark matter (DM) in 12 of them and no more than 40 per cent DM mass fraction in the remaining two, in contrast to findings for several UCDs in the Virgo cluster. Some Fornax UCDs even have too high values of (M/L)* estimated using the Kroupa stellar initial mass function (IMF) resulting in negative formally computed DM mass fractions. The objects with too high (M/L)* ratios compared to the dynamical ones have relatively short dynamical relaxation time-scales, close to the Hubble time or below. We therefore suggest that their lower dynamical ratios (M/L)dyn are caused by low-mass star depletion due to dynamical evolution. Overall, the observed UCD characteristics suggest at least two formation channels: tidal threshing of nucleated dwarf galaxies for massive UCDs (≃108 M⊙), and a classical scenario of red globular cluster formation for lower-mass UCDs (≲107 M⊙).
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