- ID:
- ivo://CDS.VizieR/J/A+A/545/A54
- Title:
- Danks 1, Danks 2, and RCW 79 variables
- Short Name:
- J/A+A/545/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ESO Public Survey "VISTA Variables in the Via Lactea"' (VVV) provides deep multi-epoch infrared observations for unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. The VVV observations will foster the construction of a sample of Galactic star clusters with reliable and homogeneously derived physical parameters (e.g., age, distance, and mass, etc.). In this first paper in a series, the methodology employed to establish cluster parameters for the envisioned database are elaborated upon by analysing four known young open clusters: Danks1, Danks2, RCW79, and DBS132. The analysis offers a first glimpse of the information that can be gleaned from the VVV observations for clusters in the final database. Wide-field, deep JHK_s_ VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results are inferred from VVV near-infrared photometry and numerous low resolution spectra (typically more than 10 per cluster). The high quality of the spectra and the deep wide-field VVV photometry enables us to precisely and independently determine the characteristics of the clusters studied, which we compare to previous determinations. An anomalous reddening law in the direction of the Danks clusters is found, specifically E(J-H)/E(H-Ks)=2.20+/-0.06, which exceeds published values for the inner Galaxy. The G305 star forming complex, which includes the Danks clusters, lies beyond the Sagittarius-Carina spiral arm and occupies the Centaurus arm. Finally, the first deep infrared colour-magnitude diagram of RCW79 is presented, which reveals a sizeable pre-main sequence population. A list of candidate variable stars in G305 region is reported. This study demonstrates the strength of the dataset and methodology employed, and constitutes the first step of a broader study which shall include reliable parameters for a sizeable number of poorly characterised and/or newly discovered clusters.
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Search Results
- ID:
- ivo://CDS.VizieR/B/dao
- Title:
- DAO Science Archive observations
- Short Name:
- B/dao
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The DAO archives are operated by the Canadian Astronomy Data Centre (CADC). These consist of two separate collections: the DAO Science Archive and the DAO Spectroscopic Plate Archive. The DAO Science Archive consists of modern electronic data obtained with the DAO's 1.8-m Plaskett telescope as well as the 1.2-m telescope and McKellar spectrograph. This collection is updated on a daily basis with new data and, as time permits, archival CCD data are also being added. The DAO spectroscopic plate collection in its entirety consists of over 16,800 high-dispersion spectrograms exposed at the coude focus of the 1.2-m DAO telescope and McKellar spectrograph between 1962 and 2000, and more than 93,000 secured at the Cassegrain focus of the DAO 1.8-m telescope and spectrograph between 1918 and 1984. The very great majority of those plates is now in the NRC-Herzberg plate archive. Since a programme to digitize them with the modified in-house PDS has only recently commenced (and with limited resources) there is currently a rather modest number of digital files available for download. However, if you have questions about the availability of plates of a target of particular interest you can we encourage you to contact Elizabeth Griffin or David Bohlender at NRC-Herzberg (elizabeth.griffin@nrc-cnrc.gc.ca), david.bohlender@nrc-cnrc.gc.ca) so that we can search the collection for plates that may be of interest to your research. Both archives allow searches by important criteria such as object name, date, and wavelength and presents the results of the search in a tabular format. The CADC's Data Retrieval facility allows archive users to download archival data directly to their own computers. Proprietary data can also be retrieved, but only by the Principal Investigator (PI) of the science program in question and any colleagues the PI has granted access to that program's data. These users must also register with the CADC in order to enable authorization tests to be made before such proprietary data is accessed. The proprietary period for DAO pixel data is 12 months from the time of the observation. Metadata associated with the pixel data (i.e. the FITS header) is public immediately. Because of uncertainties in the absolute pointing accuracy of the DAO telescopes, it is recommended that a relatively large search radius (e.g. 5') be used in any DAO archive searches for specific targets.
- ID:
- ivo://CDS.VizieR/J/A+AS/141/175
- Title:
- Dark clouds imaging polarimetry
- Short Name:
- J/A+AS/141/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A set of eight Bok Globules CB3, CB25, CB39, CB52, CB54, CB58, CB62 and CB246 were observed polarimetrically in white light, using our Imaging Polarimater (IMPOL), from the 1.2m IR telescope at Mount Abu, India. The observations were carried out on different nights during the period December 1997 and April 1998. The CCD images obtained from the instrument (IMPOL) were analyzed, to produce polarization map of the Bok Globules. The stars in the field, which are mostly background to the cloud show typically 2% linear polarization. Clouds which are less dynamic (having ^12^CO line widths {Delta}V<2.5km/s) in general show slightly better alignment of polarization vectors with the projected direction of galactic plane. On the other hand, the more dynamic group of clouds has polarization vectors more scattered and poorly aligned with the projected direction of the galactic plane. However one of the clouds observed, CB58, does not follow this trend very well.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A35
- Title:
- Dark dust and single-cloud sightlines in ISM
- Short Name:
- J/A+A/641/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as KI, that show at a resolving power of {lambda}{Delta}{lambda}~75000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH^+^ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH^+^>1) clouds, but {is frequently absent} in warm clouds. We inspected the WISE (3-22um) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar CaII distance scale, and compared these two distance estimates with GAIA parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of GAIA, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by >~ 1um large grains and predominately appears in the field of the cold interstellar medium.
- ID:
- ivo://CDS.VizieR/J/AJ/162/207
- Title:
- Dark-floored pits in Sputnik Planitia on Pluto
- Short Name:
- J/AJ/162/207
- Date:
- 02 Feb 2022 06:18:01
- Publisher:
- CDS
- Description:
- Sputnik Planitia, Pluto's gigantic, volatile ice glacier, hosts numerous scientific mysteries, including the presence of thousands of elongated pit structures. We examine various attributes of these pit structures in New Horizons data sets, revealing their length, aspect ratio, and orientation properties; we also study their reflectivities, colors, and compositions, and compare these attributes to some other relevant regions on Pluto. We then comment on origin mechanisms of the pits and also the fate of the missing volatiles represented by the pits on Sputnik Planitia. From a sample of 317 pits, we find typical length/width ratios of 2-4, with their major axis preferentially oriented approximately north-south. We also find that the floors of large pits in our sample have similar single-scattering albedos and colors to dark material on crater rims and floors (i.e., possible subsurface windows) in Burney basin. We also find that the base of the three pits in our sample, large enough to study with LEISA IR spectroscopy, display both CH_4_ and N_2_ absorption features, as do the dark regions in crater windows in Burney basin. Evidence for a sublimation erosion origin for the pits is supported over both the explosion/ejecta venting and structural collapse alternatives. Finally, we find that the mass lost by the pits on Sputnik Planitia most likely lies condensed elsewhere, on Pluto's surface, relocated there by volatile transport as opposed to removal by escape to space or photochemical conversion.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/477
- Title:
- Dark matter annihilation in galaxy clusters
- Short Name:
- J/MNRAS/425/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusters of galaxies are potentially important targets for indirect searches for dark matter (DM) annihilation. Here we reassess the detection prospects for annihilation in massive haloes, based on a statistical investigation of 1743 clusters in the new Meta-Catalogue of X-ray Clusters (MCXC). We derive a new limit for the extragalactic DM annihilation background of at least 20 per cent of that originating from the Galaxy for an integration angle of 0.1{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/L51
- Title:
- Dark matter densities in cluster isochrones
- Short Name:
- J/ApJ/733/L51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to characterize how dark matter (DM) annihilation inside stars changes the aspect of a stellar cluster, we computed the evolution until the ignition of the He burning of stars from 0.7M_{sun}_ to 3.5M_{sun}_ within halos of DM with different characteristics. We found that, when a cluster is surrounded by a dense DM halo, the positions of the cluster' stars in the H-R diagram have a brighter and hotter turnoff point than in the classical scenario without DM, therefore giving the cluster a younger appearance. The high DM densities required to produce these effects are expected only in very specific locations, such as near the center of our Galaxy. In particular, if DM is formed by the 8 GeV weakly interacting massive particles recently invoked to reconcile the results from direct detection experiments, then this signature is predicted for halos of DM with a density {rho}_{chi}_=3x10^5^GeV/cm^3^. A DM density gradient inside the stellar cluster would result in a broader main sequence, turnoff, and red giant branch regions. Moreover, we found that for very high DM halo densities the bottom of the isochrones in the H-R diagram rises to higher luminosities, leading to a characteristic signature on the stellar cluster. We argue that this signature could be used to indirectly probe the presence of DM particles in the location of a cluster.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/31
- Title:
- Dark matter halo models for SPARC galaxies
- Short Name:
- J/ApJS/247/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present rotation curve fits to 175 late-type galaxies from the Spitzer Photometry and Accurate Rotation Curves database using seven dark matter (DM) halo profiles: pseudo-isothermal, Burkert, Navarro-Frenk-White (NFW), Einasto, Di Cintio+ (DC14; 2014MNRAS.441.2986D), cored-NFW, and a new semi-empirical profile named Lucky13. We marginalize over the stellar mass-to-light ratio, galaxy distance, disk inclination, halo concentration, and halo mass (and an additional shape parameter for Einasto) using a Markov Chain Monte Carlo method. We find that cored halo models, such as the DC14 and Burkert profiles, generally provide better fits to rotation curves than the cuspy NFW profile. The stellar mass-halo mass relation from abundance matching is recovered by all halo profiles once imposed as a Bayesian prior, whereas the halo mass-concentration relation is not reproduced in detail by any halo model.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/1526
- Title:
- Dark matter in dSph galaxies
- Short Name:
- J/MNRAS/418/1526
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Due to their large dynamical mass-to-light ratios, dwarf spheroidal galaxies (dSphs) are promising targets for the indirect detection of dark matter (DM) in {gamma}-rays. We examine their detectability by present and future {gamma}-ray observatories. The key innovative features of our analysis are as follows: (i) we take into account the angular size of the dSphs; while nearby objects have higher {gamma}-ray flux, their larger angular extent can make them less attractive targets for background-dominated instruments; (ii) we derive DM profiles and the astrophysical J-factor (which parametrizes the expected {gamma}-ray flux, independently of the choice of DM particle model) for the classical dSphs directly from photometric and kinematic data. We assume very little about the DM profile, modelling this as a smooth split-power-law distribution, with and without subclumps; (iii) we use a Markov chain Monte Carlo technique to marginalize over unknown parameters and determine the sensitivity of our derived J-factors to both model and measurement uncertainties; and (iv) we use simulated DM profiles to demonstrate that our J-factor determinations recover the correct solution within our quoted uncertainties.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/74
- Title:
- Dark matter profiles in dwarf galaxies
- Short Name:
- J/ApJ/801/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gamma-ray searches for dark matter annihilation and decay in dwarf galaxies rely on an understanding of the dark matter density profiles of these systems. Conversely, uncertainties in these density profiles propagate into the derived particle physics limits as systematic errors. In this paper we quantify the expected dark matter signal from 20 Milky Way dwarfs using a uniform analysis of the most recent stellar-kinematic data available. Assuming that the observed stellar populations are equilibrium tracers of spherically symmetric gravitational potentials that are dominated by dark matter, we find that current stellar-kinematic data can predict the amplitudes of annihilation signals to within a factor of a few for the ultra-faint dwarfs of greatest interest. On the other hand, the expected signal from several classical dwarfs (with high-quality observations of large numbers of member stars) can be localized to the ~20% level. These results are important for designing maximally sensitive searches in current and future experiments using space and ground-based instruments.