- ID:
- ivo://CDS.VizieR/J/ApJ/735/L22
- Title:
- HUDF galaxy properties at z~2
- Short Name:
- J/ApJ/735/L22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use ultra-deep Hubble Space Telescope Wide Field Camera 3/infrared imaging of the Hubble Ultra Deep Field to investigate the rest-frame optical morphologies of a mass-selected sample of galaxies at z~2. We find a large variety of galaxy morphologies, ranging from large, blue, disk-like galaxies to compact, red, early-type galaxies. We derive rest-frame u-g color profiles for these galaxies and show that most z~2 galaxies in our sample have negative color gradients such that their cores are red.
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Search Results
- 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.
- 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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/135/823
- Title:
- ICMF of super star clusters
- Short Name:
- J/AJ/135/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial cluster mass function (ICMF) is a fundamental property of star formation in galaxies. To gauge its universality, we measure and compare the ICMFs in irregular and spiral galaxies. Our sample of irregular galaxies is based on 13 nearby galaxies selected from a volume-limited sample from the fifth data release of the Sloan Digital Sky Survey (SDSS), from which about 320 young (<=20Myr), massive (>~3x10^49M_{sun}_) clusters or associations were selected using an automated source extraction routine. The extinctions, ages, and masses were determined by comparing their u'g'i'z' magnitudes to those generated from starburst models.
- ID:
- ivo://CDS.VizieR/J/ApJ/588/218
- Title:
- i*g* photometry of SDSS EDR galaxies
- Short Name:
- J/ApJ/588/218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present a new statistic for quantifying galaxy morphology based on measurements of the Gini coefficient of galaxy light distributions. This statistic is easy to measure and is commonly used in econometrics to measure how wealth is distributed in human populations. When applied to galaxy images, the Gini coefficient provides a quantitative measure of the inequality with which a galaxy's light is distributed among its constituent pixels. We measure the Gini coefficient of local galaxies in the Early Data Release of the Sloan Digital Sky Survey and demonstrate that this quantity is closely correlated with measurements of central concentration, but with significant scatter.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A157
- Title:
- 5 ILRTs light curves and spectra
- Short Name:
- J/A+A/654/A157
- Date:
- 07 Mar 2022 07:10:34
- Publisher:
- CDS
- Description:
- We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between -11:5 and -14:5mag. Their pseudo-bolometric light curves peak in the range 0.5-9.0*10^40^erg/s and their total radiated energies are on the order of (0.3-3)*10^47^erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the ^56^Co decay. If the late-time power source is indeed radioactive decay, these transients produce ^56^Ni masses on the order of 10^-4^ to 10^-3^M_{sun}_. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km/s, along with CaII features. In particular, the [CaII]7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/24
- Title:
- Imaging observations of iPTF 13ajg
- Short Name:
- J/ApJ/797/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging and spectroscopy of a hydrogen-poor superluminous supernova (SLSN) discovered by the intermediate Palomar Transient Factory, iPTF 13ajg. At a redshift of z=0.7403, derived from narrow absorption lines, iPTF 13ajg peaked at an absolute magnitude of M_u,AB_=-22.5, one of the most luminous supernovae to date. The observed bolometric peak luminosity of iPTF 13ajg is 3.2x10^44^ erg/s, while the estimated total radiated energy is 1.3x10^51^ erg. We detect narrow absorption lines of Mg I, Mg II, and Fe II, associated with the cold interstellar medium in the host galaxy, at two different epochs with X-shooter at the Very Large Telescope. From Voigt profile fitting, we derive the column densities log N(Mg I)=11.94+/-0.06, log N(Mg II)=14.7+/-0.3, and log N(Fe II)=14.25+/-0.10. These column densities, as well as the Mg I and Mg II equivalent widths of a sample of hydrogen-poor SLSNe taken from the literature, are at the low end of those derived for gamma-ray bursts (GRBs) whose progenitors are also thought to be massive stars. This suggests that the environments of hydrogen-poor SLSNe and GRBs are different. From the nondetection of Fe II fine-structure absorption lines, we derive a lower limit on the distance between the supernova and the narrow-line absorbing gas of 50 pc. The neutral gas responsible for the absorption in iPTF 13ajg exhibits a single narrow component with a low velocity width, {Delta}V=76 km/s, indicating a low-mass host galaxy. No host galaxy emission lines are detected, leading to an upper limit on the unobscured star formation rate (SFR) of SFR_[OII]_<0.07 M_{sun}_/yr. Late-time imaging shows the iPTF 13ajg host galaxy to be faint, with g_AB_~27.0 and R_AB_>=26.0 mag, corresponding to M_B,Vega_>~-17.7 mag.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/159
- Title:
- Interferometric CO obs. of 126 CALIFA galaxies
- Short Name:
- J/ApJ/846/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3{sigma} sensitivity {Sigma}_mol_~11M_{sun}/pc^2^ before inclination correction, resolution ~1.4kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.
