- ID:
- ivo://CDS.VizieR/J/ApJ/756/117
- Title:
- HyperLeda sample of nearby elliptical galaxies
- Short Name:
- J/ApJ/756/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the effect of the environment on the Faber-Jackson (FJ) relation, using a sample of 384 nearby elliptical galaxies and estimating objectively their environment on the typical scale of galaxy clusters. We show that the intrinsic scatter of the FJ relation is significantly reduced when ellipticals in high-density environments are compared to ellipticals in low-density ones. This result, which holds in a limited range of overdensities, is likely to provide an important observational link between scaling relations and formation mechanisms in galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/882/181
- Title:
- Hyper-luminous X-ray sources from SDSS and CSC2
- Short Name:
- J/ApJ/882/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hyper-luminous X-ray sources (HLXs; L_X_>10^41^erg/s) are off-nuclear X-ray sources in galaxies and strong candidates for intermediate-mass black holes (IMBHs). We have constructed a sample of 169 HLX candidates by combining X-ray detections from the Chandra Source Catalog (Version 2) with galaxies from the Sloan Digital Sky Survey and registering individual images for improved relative astrometric accuracy. The spatial resolution of Chandra allows for the sample to extend out to z~0.9. Optical counterparts are detected among one-fourth of the sample, one-third of which are consistent with dwarf galaxy stellar masses. The average intrinsic X-ray spectral slope indicates efficient accretion, potentially driven by galaxy mergers, and the column densities suggest one-third of the sample has significant X-ray absorption. We find that 144 of the HLX candidates have X-ray emission that is significantly in excess of the expected contribution from star formation and hot gas, strongly suggesting that they are produced by accretion onto black holes more massive than stars. After correcting for an average background or foreground contamination rate of 8%, we estimate that at least ~20 of the HLX candidates are consistent with IMBH masses, and this estimate is potentially several times higher assuming more efficient accretion. This catalog currently represents the largest sample of uniformly selected, off-nuclear IMBH candidates. These sources may represent scenarios in which a low-mass galaxy hosting an IMBH has merged with a more massive galaxy and provide an excellent sample for testing models of low-mass BH formation and merger-driven growth.
6723. Hypervelocity stars. II.
- ID:
- ivo://CDS.VizieR/J/ApJ/660/311
- Title:
- Hypervelocity stars. II.
- Short Name:
- J/ApJ/660/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hypervelocity stars (HVSs) are stars ejected completely out of the Milky Way by three-body interactions with the massive black hole in the Galactic center. We describe 643 new spectroscopic observations from our targeted survey for HVSs. We find a significant (3.5{sigma}) excess of B-type stars with large velocities +275km/s<V_rf_<450km/s and distances d>10kpc that are most plausibly explained as a new class of HVSs: stars ejected from the Galactic center on bound orbits. If a Galactic center ejection origin is correct, the distribution of HVSs on the sky should be anisotropic for a survey complete to a fixed limiting apparent magnitude. The unbound HVSs in our survey have a marginally anisotropic distribution on the sky, consistent with the Galactic center ejection picture.
6724. Hypervelocity stars. III
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1708
- Title:
- Hypervelocity stars. III
- Short Name:
- J/ApJ/671/1708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of three new unbound hypervelocity stars (HVSs), stars travelling with such extreme velocities that dynamical ejection from a massive black hole (MBH) is their only suggested origin. We also detect a population of possibly bound HVSs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/1359
- Title:
- IAC Stripe 82 Legacy Project: Photometry
- Short Name:
- J/MNRAS/456/1359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Stripe 82 covers 275 square degrees within -50{deg}<=RA<=+60{deg} and -1.26{deg}<=DE<=+1.25{deg}. We discuss the steps of our reduction which puts special emphasis on preserving the characteristics of the background (sky + diffuse light) in the input images using a non-aggressive sky subtraction strategy. Our reduction reaches a limit of ~28.5 mag/arcsec^2^ (3{sigma}, 10x10 arcsec^2^) in the r band. The effective surface brightness limit (50 per cent completeness for exponential light distribution) lies at <{mu}e(r)>~25.5mag/arcsec^2^. For point sources, we reach 50 per cent completeness limits (3{sigma} level) of (24.2, 25.2, 24.7, 24.3, 23.0) mag in (u, g, r, i, z). This is between 1.7 and 2.0mag deeper than the single-epoch SDSS releases. The co-adds show point spread functions (PSFs) with median full width at half-maximum values ranging from 1-arcsec in i and z to 1.3-arcsec in the u band. The imaging data are made publicly available at http://www.iac.es/proyecto/stripe82. The release includes deep co-adds and representations of the PSF for each field. Additionally, we provide object catalogues with stars and galaxies confidently separated until g~23mag. The IAC Stripe 82 co-adds offer a rather unique possibility to study the low surface brightness Universe, exemplified by the discovery of stellar streams around NGC 0426 and NGC 0936. We also discuss further science cases like stellar haloes and disc truncations, low surface brightness galaxies, the intracluster light in galaxy clusters and the diffuse emission of Galactic dust known as Galactic Cirrus.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/102
- Title:
- I-band GALFIT analysis of luminous infrared galaxies
- Short Name:
- J/ApJ/768/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L_IR_>10^11.4^ L_{sun}_) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W "I-band" images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64+/-0.62 mag (1.8_-0.4_^+1.4^ L_1_^*^), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger advances. In contrast, the fraction of nuclear PSFs increases toward later merger stages and is highest in late-stage systems with a single nucleus. Thus, light from an active galactic nucleus or compact nuclear star cluster is more visible at I band as ULIRGs enter their latter stages of evolution. Finally, both GOALS elliptical hosts and nearby Sloan Digital Sky Survey (SDSS) ellipticals occupy the same part of the surface brightness versus half-light radius plot (i.e., the "Kormendy Relation") and have similar slopes, consistent with the possibility that the GOALS galaxies belong to the same parent population as the SDSS ellipticals.
- ID:
- ivo://CDS.VizieR/J/AJ/152/164
- Title:
- I-band light curves of OGLE LMC Miras
- Short Name:
- J/AJ/152/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequency parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period-luminosity relations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/1753
- Title:
- I-band light curves of SNe II from OGLE-IV
- Short Name:
- J/MNRAS/449/1753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 11 Type II supernovae (SNe) discovered by the OGLE-IV survey. All objects have well-sampled I-band light curves, and at least one spectrum. We find that two or three of the 11 SNe have a declining light curve, and spectra consistent with other SNe II-L, while the rest have plateaus that can be as short as 70 d, unlike the 100 d typically found in nearby galaxies. The OGLE SNe are also brighter, and show that magnitude-limited surveys find SNe that are different than usually found in nearby galaxies. We discuss this sample in the context of understanding Type II SNe as a class and their suggested use as standard candles.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1935
- Title:
- I-band photometry of cosmic flows
- Short Name:
- J/MNRAS/415/1935
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within the "Cosmic Flows" project, I-band photometry of 524 relatively nearby galaxies has been carried out over the course of several years with the University of Hawaii 2.2-m telescope and a camera with a 7.5-arcmin field of view. The primary scientific goal was to provide global magnitudes and inclinations for galaxies for the purpose of measuring distances through the correlation between galaxy luminosities and rotation rates. The 1{sigma} accuracy on a total magnitude is 0.08mag. The observations typically extend to 7-8 exponential disc scalelengths, so the data are useful for studies of the structural properties of galaxies.
- ID:
- ivo://CDS.VizieR/II/362
- Title:
- i-band variability of YSOs
- Short Name:
- II/362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an i-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, which samples timescales from 1 minute to ten years. Using structure functions we show that on all timescales (tau) there is a monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e. the more evolved systems are less variable. The Class Is show an approximately power-law increase (tau^0.8^) in variability from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively different behaviour with most showing a power-law increase in variability to a timescale corresponding to the rotational period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all Class IIs have two primary components to their variability. The first is an underlying roughly power-law variability spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component is an approximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longer-timescale variability have a smaller rotational modulation either because they are seen at low inclinations or have more complex magnetic field geometries. We derive a new way of calculating structure functions for large simulated datasets (the "fast structure function"), based on fast Fourier transforms.