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1661. Distant radio galaxies in southern hemisphere
ID:
ivo://CDS.VizieR/J/MNRAS/394/2197
Title:
Distant radio galaxies in southern hemisphere
Short Name:
J/MNRAS/394/2197
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have compiled a sample of 234 ultra-steep-spectrum (USS) selected radio sources in order to find high-redshift radio galaxies. The sample covers the declination range -40{deg}<{delta}<-30{deg} in the overlap region between the 1400-MHz National Radio Astronomy Observatory (NRAO) Very Large Array (VLA) Sky Survey (NVSS), 408-MHz Revised Molonglo Reference Catalogue and the 843-MHz Sydney University Molonglo Sky Survey (the MRCR-SUMSS sample). This is the second in a series of papers on the MRCR-SUMSS sample, and here we present the K-band (2.2{mu}m) imaging of 173 of the sources primarily from the Magellan and the Anglo-Australian Telescopes. We detect a counterpart to the radio source in 93 per cent of the new K-band images which, along with previously published data, makes this the largest published sample of K-band counterparts to USS-selected radio galaxies. The location of the K-band identification has been compared to the features of the radio emission for the double sources. We find that the identification is most likely to lie near the mid-point of the radio lobes rather than closer to the brighter lobe, making the centroid a less likely place to find the optical counterpart. 79 per cent of the identifications are less than 1arcsec from the radio lobe axis. These results differ from studies of low-redshift radio samples where the environments are typically not nearly so dense and disturbed as those at high redshift. In contrast to some literature samples, we find that the majority of our sample shows no alignment between the near-infrared and radio axes. Several different morphologies of aligned structures are found and those that are aligned within 10{deg} are consistent with jet-induced star formation. The distribution and median value of the K-band magnitudes for the MRCR-SUMSS sample are found to be similar to several other USS-selected samples even though each sample has a very different median 1400MHz flux density. USS selection from a lower radio-frequency sample has not netted fainter K-band magnitudes, which may imply that the k-correction is not responsible for the effectiveness of USS selection.
1662. Distant RR Lyrae stars discovered with HiTS
ID:
ivo://CDS.VizieR/J/ApJ/855/43
Title:
Distant RR Lyrae stars discovered with HiTS
Short Name:
J/ApJ/855/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of distant RR Lyrae stars, including the most distant known in the Milky Way, using data taken in the g-band with the Dark Energy Camera as part of the High cadence Transient Survey (HiTS; 2014 campaign). We detect a total of 173 RR Lyrae stars over a ~120deg^2^ area, including both known RR Lyrae and new detections. The heliocentric distances dH of the full sample range from 9 to >200kpc, with 18 of them beyond 90kpc. We identify three sub-groups of RR Lyrae as members of known systems: the Sextans dwarf spheroidal galaxy, for which we report 46 new discoveries, and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology, we fit spherical and ellipsoidal profiles of the form {rho}(R)~Rn to the radial density distribution of RR Lyrae in the Galactic halo. The best fit corresponds to the spherical case, for which we obtain a simple power-law index of n=-4.17_-0.20_^+0.18^, consistent with recent studies made with samples covering shorter distances. The pulsational properties of the outermost RR Lyrae in the sample (dH>90kpc) differ from the ones in the halo population at closer distances. The distribution of the stars in a period-amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups, similar to what is found in the ultra-faint dwarf satellites around the Milky Way. The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo.
1663. Distant spheroids in the GOODS fields
ID:
ivo://CDS.VizieR/J/ApJ/680/70
Title:
Distant spheroids in the GOODS fields
Short Name:
J/ApJ/680/70
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the first results of a new study aimed at understanding the diversity and evolutionary history of distant galactic bulges in the context of now well-established trends for pure spheroidal galaxies. To this end, bulges have been isolated for a sample of 137 spiral galaxies within the redshift range 0.1<z<1.2 in the GOODS fields. Using proven photometric techniques, we determine the characteristic parameters (size, surface brightness, profile shape) of both the disk and bulge components in our sample. In agreement with earlier work that utilized aperture colors, distant bulges show a broader range of optical colors than would be the case for passively evolving populations. To quantify the amount of recent star formation necessary to explain this result, we used DEIMOS to secure stellar velocity dispersions for a sizeable fraction of our sample. This has enabled us to compare the fundamental plane of our distant bulges with that for spheroidal galaxies in a similar redshift range.
1664. DK Cygni light curve
ID:
ivo://CDS.VizieR/J/A+A/289/137
Title:
DK Cygni light curve
Short Name:
J/A+A/289/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
1665. 3D kinematic observations of stars in Galactic Centre
ID:
ivo://CDS.VizieR/J/ApJ/779/L6
Title:
3D kinematic observations of stars in Galactic Centre
Short Name:
J/ApJ/779/L6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present three-dimensional (3D) kinematic observations of stars within the central 0.5pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface density profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial density profile, cluster velocity anisotropy, black hole mass (M_BH_), and distance to the Galactic center (R_0_) simultaneously. We find that the inner stellar density profile of the late-type stars, {rho}(r){prop.to}r^-{gamma}^, have a power law slope {gamma}=0.05_-0.60^+0.29^, much more shallow than the frequently assumed Bahcall-Wolf slope of {gamma}=7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M_BH_=5.76_-1.26_^+1.76^x10^6^M_{sun}_ and R_0_=8.92_-0.55_^+0.58^kpc is consistent with that derived from stellar orbits within 1" of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R_0_ is reduced by 30% (8.46_-0.38_^+0.42^kpc). We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R_0_.
1666. DK Lac V light curves
ID:
ivo://CDS.VizieR/J/AJ/141/122
Title:
DK Lac V light curves
Short Name:
J/AJ/141/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on extensive photometry of DK Lac obtained during the interval 1990-2009, which includes a 2mag low state during 2001-2003. Much of the photometry consists of exposures obtained with a typical spacing of several days, but also includes 26 sequences of continuous photometry each lasting 2-7hr. We find no evidence for periodicities in our data.
1667. DL Cygni ubr differential photometry
ID:
ivo://CDS.VizieR/J/A+A/349/515
Title:
DL Cygni ubr differential photometry
Short Name:
J/A+A/349/515
Date:
21 Oct 2021
Publisher:
CDS
Description:
Relative photometry of DL Cygni versus GSC 3595-0200 in the instrumental system
1668. DM Cyg BVIc light curves
ID:
ivo://CDS.VizieR/J/MNRAS/397/350
Title:
DM Cyg BVIc light curves
Short Name:
J/MNRAS/397/350
Date:
21 Oct 2021
Publisher:
CDS
Description:
DM Cyg, a fundamental mode RRab star, was observed in the 2007 and 2008 seasons in the framework of the Konkoly Blazhko Survey. Very small amplitude light-curve modulation was detected with 10.57d modulation period. The maximum brightness and phase variations do not exceed 0.07mag and 7min, respectively. In spite of the very small amplitude of the modulation, beside the frequency triplets characterizing the Fourier spectrum of the light curve, two quintuplet components were also identified. The accuracy and the good phase coverage of our observations made it possible to analyse the light curves at different phases of the modulation separately.
1669. DoAr 44 ugri light curves
ID:
ivo://CDS.VizieR/J/A+A/643/A99
Title:
DoAr 44 ugri light curves
Short Name:
J/A+A/643/A99
Date:
21 Oct 2021
Publisher:
CDS
Description:
Young stars interact with their accretion disk through their strong magnetosphere. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). We monitored the system over several rotational cycles, combining high-resolution spectropolarimetry at both optical and near-IR wavelengths with long-baseline near-IR inteferometry and multicolor photometry. We derive a rotational period of 2.96d from the system's light curve, which is dominated by stellar spots. We fully characterize the central star's properties from the high signal-to-noise, high-resolution optical spectra we obtained during the campaign. DoAr 44 is a young 1.2M_{sun}_ star, moderately accreting from its disk (Macc=6.510^-9^M_{sun}_/yr), and seen at a low inclination (i~=30{deg}). Several optical and near-IR line profiles probing the accretion funnel flows (H{alpha}, H{beta}, HeI 1083nm, Pa{beta}) and the accretion shock (HeI 587.6nm) are modulated at the stellar rotation period. The most variable line profile is HeI 1083nm, which exhibits modulated redshifted wings that are a signature of accretion funnel flows, as well as deep blueshifted absorptions indicative of transient outflows. The Zeeman-Doppler analysis suggests the star hosts a mainly dipolar magnetic field, inclined by about 20{deg} onto the spin axis, with an intensity reaching about 800G at the photosphere, and up to 2+/-0.8kG close to the accretion shock. The magnetic field appears strong enough to disrupt the inner disk close to the corotation radius, at a distance of about 4.6R* (0.043au), which is consistent with the 5R* (0.047au) upper limit we derived for the size of the magnetosphere in our Paper I from long baseline interferometry. DoAr 44 is a pre-transitional disk system, exhibiting a 25-30au gap in its circumstellar disk, with the inner and outer disks being misaligned. On a scale of 0.1au or less, our results indicate that the system is steadily accreting from its inner disk through its tilted dipolar magnetosphere. We conclude that in spite of a highly structured disk on the large scale, perhaps the signature of ongoing planetary formation, the magnetospheric accretion process proceeds unimpeded at the star-disk interaction level.
1670. Dolidze 25 Chandra/ACIS-I X-ray sources
ID:
ivo://CDS.VizieR/J/A+A/650/A157
Title:
Dolidze 25 Chandra/ACIS-I X-ray sources
Short Name:
J/A+A/650/A157
Date:
22 Feb 2022
Publisher:
CDS
Description:
The dispersal of protoplanetary disks sets the timescale available for planets to assemble, and thus it is one of the fundamental parameters in theories of planetary formation. Disk dispersal is determined by several properties of the central star, the disk itself, and the surrounding environment. In particular, the metallicity of disks may impact their evolution, even if to date controversial results exist: in low-metallicity clusters disks seem to rapidly disperse, while in the Magellanic Clouds some evidence supports the existence of accreting disks few tens of Myrs old. In this paper we study the dispersal timescale of disks in Dolidze 25, the young cluster in proximity of the Sun with lowest metallicity, with the aim of understanding whether disk evolution is impacted by the low-metallicity of the cluster. We have analyzed Chandra/ACIS-I observations of the cluster and combined the resulting source catalog with existing optical and infrared catalogs of the region. We selected the disk-bearing population in a 1 degree circular region centered on Dolidze~25 from criteria based on infrared colors, and the disk-less population within a smaller central region among the X-ray sources with OIR counterpart. In both cases, criteria are applied to discard contaminating sources in the foreground/background. We have derived stellar parameters from isochrones fitted to color-magnitude diagrams. We derived a disk fraction of about 34% and a median age of the cluster of 1.2Myrs. To minimize the impact of incompleteness and spatial inhomogeneity of the list of members, we restricted this calculation to stars in a magnitude range where our selection of cluster members is fairly complete and by adopting different cuts in stellar masses. By comparing this estimate with existing estimates of the disk fraction of clusters younger than 10Myrs, our study suggests that the disk fraction of Dolidze 25 is lower than what is expected from its age alone. Even if our results are not conclusive given the intrinsic uncertainty on stellar ages estimated from isochrones fitting to color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be impacted by the environment. Given the poor O star population and low stellar density of the cluster, it is more likely that disks dispersal timescale is dictated more by the low metallicity of the cluster rather than external photoevaporation or dynamical encounters.