- ID:
- ivo://CDS.VizieR/J/ApJ/705/1646
- Title:
- Debris disks in Upper Sco
- Short Name:
- J/ApJ/705/1646
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present MIPS 24um and 70um photometry for 205 members of the Upper Scorpius OB Association. These data are combined with published MIPS photometry for 15 additional association members to assess the frequency of circumstellar disks around 5Myr old stars with spectral types between B0 and M5. Twelve stars have a detectable 70um excess, each of which also has a detectable 24um excess. A total of 54 stars are identified with a 24um excess more than 32% above the stellar photosphere. The MIPS observations reveal 19 excess sources - 8 A/F/G stars and 11 K/M stars - that were not previously identified with an 8um or 16um excess. The lack of short-wavelength emission and the weak 24um excess suggests that these sources are debris systems or the remnants of optically thick primordial disks with inner holes. Despite the wide range of luminosities of the stars hosting apparent debris systems, the excess characteristics are consistent with all stars having dust at similar orbital radii after factoring in variations in the radiation blowout particle size with spectral type. The results for Upper Sco are compared to similar photometric surveys from the literature to re-evaluate the evolution of debris emission.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/887/19
- Title:
- DECam phot. of Gaia stars in Price-Whelan 1
- Short Name:
- J/ApJ/887/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a young ({tau}~117Myr), low-mass (M~1200M_{sun}_), metal-poor ([Fe/H]~-1.14) stellar association at a heliocentric distance D~28.7kpc, placing it far into the Milky Way (MW) halo. At its present Galactocentric position (R,z)~(23,15)kpc, the association is (on the sky) near the leading arm of the gas stream emanating from the Magellanic Cloud system, but is located ~60{deg} from the Large Magellanic Cloud center on the other side of the MW disk. If the cluster is colocated with HI gas in the stream, we directly measure the distance to the leading arm of the Magellanic stream. The measured distance is inconsistent with Magellanic stream model predictions that do not account for ram pressure and gas interaction with the MW disk. The estimated age of the cluster is consistent with the time of last passage of the leading arm gas through the Galactic midplane; we therefore speculate that this star formation event was triggered by its last disk midplane passage. Most details of this idea remain a puzzle: the Magellanic stream has low column density, the MW disk at large radii has low gas density, and the relative velocity of the leading arm and MW gas is large. However it formed, the discovery of a young stellar cluster in the MW halo presents an interesting opportunity for study. This cluster was discovered with Gaia astrometry and photometry alone, but follow-up DECam photometry was crucial for measuring its properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/L13
- Title:
- DECam r and i magnitudes in the Fornax 6 cluster
- Short Name:
- J/ApJ/875/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since first noticed by Shapley in 1939, a faint object coincident with the Fornax dwarf spheroidal has long been discussed as a possible sixth globular cluster (GC) system. However, debate has continued over whether this overdensity is a statistical artifact or a blended galaxy group. In this Letter we demonstrate, using deep DECam imaging data, that this object is well resolved into stars and is a bona fide star cluster. The stellar overdensity of this cluster is statistically significant at the level of ~6-6.7{sigma} in several different photometric catalogs including Gaia. Therefore, it is highly unlikely to be caused by random fluctuation. We show that Fornax 6 is a star cluster with a peculiarly low surface brightness and irregular shape, which may indicate a strong tidal influence from its host galaxy. The Hess diagram of Fornax 6 is largely consistent with that of Fornax field stars, but it appears to be slightly bluer. However, it is still likely more metal-rich than most of the GCs in the system. Faint clusters like Fornax 6 that orbit and potentially get disrupted in the centers of dwarf galaxies can prove crucial for constraining the dark matter distribution in Milky Way satellites.
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/5049
- Title:
- DECam Survey of Scorpius Centaurus
- Short Name:
- J/MNRAS/484/5049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using images taken with the Dark Energy Camera (DECam), the first extensive survey of low mass and substellar objects is made in the ~15-20Myr Upper Centaurus Lupus (UCL) and Lower Centaurus Crux (LCC) subgroups of the Scorpius-Centaurus OB Association (Sco-Cen). Due to the size of our data set (>2Tb), we developed an extensive open source set of python libraries to reduce our images, including astrometry, coaddition, and PSF photometry. Our survey consists of 29x3deg^2^ fields in the UCL and LCC subgroups of Sco-Cen and the creation of a catalogue with over 11 million point sources. We create a prioritized list of UCL and LCC candidate members, with 118 best and another 348 good candidates. We show that the luminosity and mass functions of our low mass and substellar candidates are consistent with measurements for the younger Upper Scorpius subgroup and estimates of a universal IMF, with spectral types ranging from M1 down to L1.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A92
- Title:
- Deep all-sky census of the Hyades
- Short Name:
- J/A+A/531/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of the PPMXL catalogue we perform an all-sky census of the Hyades down to masses of about 0.2M_{sun}_ in a region up to 30pc from the cluster centre. We use the proper motions from PPMXL in the convergent point method to determine probable kinematic members. From 2MASS photometry and CMC14 r'-band photometry, we derive empirical colour-absolute magnitude diagrams and, finally, determine photometric membership for all kinematic candidates. This is the first deep (r'<17) all-sky survey of the Hyades allowing a full three-dimensional analysis of the cluster. The survey is complete down to at least M_{K_s_}_=7.3 or 0.25M_{sun}_. We find 724 stellar systems co-moving with the bulk Hyades space velocity, which represent a total mass of 435M_{sun}_. The tidal radius is about 9pc, and 275M_{sun}_ (364 systems) are gravitationally bound. This is the cluster proper. Its mass density profile is perfectly fitted by a Plummer model with a central density of 2.21M_{sun}_/pc^3^ and a core radius of r_co_=3.10pc, while the half-mass radius is r_h_=4.1pc. There are another 100M_{sun}_ in a volume between one and two tidal radii (halo), and another 60M_{sun}_ up to a distance of 30pc from the centre. Strong mass segregation is inherent in the cluster. The present-day luminosity and mass functions are noticeably different in various parts of the cluster (core, corona, halo, and co-movers). They are strongly evolved compared to presently favoured initial mass functions. The analysis of the velocity dispersion of the cluster shows that about 20% of its members must be binaries. As a by-product, we find that presently available theoretical isochrones are not able to adequately describe the near-infrared colour-absolute magnitude relation for those cluster stars that are less massive than about 0.6M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/132/2409
- Title:
- Deep ATLAS radio observations of CDFS
- Short Name:
- J/AJ/132/2409
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from the Australia Telescope Large Area Survey, which consists of deep radio observations of a 3.7deg^2^ field surrounding the Chandra Deep Field-South, largely coincident with the infrared Spitzer Wide-Area Infrared Extragalactic (SWIRE) Survey. We also list cross-identifications to infrared and optical photometry data from SWIRE, and ground-based optical spectroscopy. A total of 784 radio components are identified, corresponding to 726 distinct radio sources, nearly all of which are identified with SWIRE sources. Of the radio sources with measured redshifts, most lie in the redshift range 0.5-2 and include both star-forming galaxies and active galactic nuclei. We identify a rare population of infrared-faint radio sources that are bright at radio wavelengths but are not seen in the available optical, infrared, or X-ray data. Such rare classes of sources can only be discovered in wide, deep surveys such as this.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/679
- Title:
- Deep blank field catalogue
- Short Name:
- J/MNRAS/427/679
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observation of blank fields, defined as regions of the sky that are devoid of stars down to a given threshold magnitude, constitutes one of the most relevant calibration procedures required for the proper reduction of astronomical data obtained following typical observing strategies. In this work, we have used the Delaunay triangulation to search for deep blank fields throughout the whole sky, with a minimum size of 10-arcmin in diameter and an increasing threshold magnitude from 15 to 18 in the R band of the USNO-B Catalog of the United States Naval Observatory. The result is a catalogue with the deepest blank fields known so far. A short sample of these regions has been tested with the 10.4m Gran Telescopio Canarias, and it has been shown to be extremely useful for medium and large size telescopes. Because some of the regions found could also be suitable for new extragalactic studies, we have estimated the galactic extinction in the direction of each deep blank field. This catalogue is accessible through the Virtual Observatory tool TESELA, and the user can retrieve - and visualise using Aladin - the deep blank fields available near a given position in the sky.
- ID:
- ivo://CDS.VizieR/J/MNRAS/261/657
- Title:
- Deep CCD photometry of Leo II
- Short Name:
- J/MNRAS/261/657
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep colour-magnitude diagram of the central 7 x 7 arcmin2 region of Leo II. The diagram shows a well-defined giant branch and a red horizontal branch, heavily populated on the red side but extending far into the blue. Having a low metallicity ([Fe/H]=-1.9), the Leo II diagram is similar to those of outer halo clusters suffering from the second-parameter syndrome. From the mean apparent magnitude of candidate RR Lyrae stars, (VHB) = 22.10, we estimate the distance of Leo II to be 215 kpc, a value similar to previous estimates. A number of variable-star candidates are identified and two new very red giants have been found. Comparison with the other dwarf spheroidals of the Local Group reveals that Leo II belongs to the group of four small and faint dwarf spheroidal galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/155/110
- Title:
- Deep CFHT imaging of VVDS-F22 field. II. Quasars
- Short Name:
- J/AJ/155/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a faint quasar survey in a one-square-degree field. The aim is to test the Y-K/g-z and J-K/i-Y color selection criteria for quasars at faint magnitudes to obtain a complete sample of quasars based on deep optical and near-infrared color-color selection and to measure the faint end of the quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y-K/g-z and J-K/i-Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5<z<4.5 and i<22.5 mag within one-square-degree field. The survey significantly increases the number of faint quasars in this field, especially at z~2-3. It confirms that our color selections are highly complete in a wide redshift range (z<4.5), especially over the quasar number density peak at z~2-3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z>2.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/20
- Title:
- Deep Chandra survey of the SMC. III. HMXBs
- Short Name:
- J/ApJ/887/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled the most complete census of high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud with the aim to investigate the formation efficiency of young accreting binaries in its low-metallicity environment. In total, we use 123 X-ray sources with detections in our Chandra X-ray Visionary Program (XVP), supplemented by 14 additional (likely and confirmed) HMXBs identified by Haberl & Sturm (2016, J/A+A/586/A81) that fall within the XVP area, but are neither detected in our survey (nine sources) nor matched with any of the 127 sources identified in the XVP data (five sources). Specifically, we examine the number ratio of the HMXBs [N(HMXBs)] to (a) the number of OB stars, (b) the local star formation rate (SFR), and (c) the stellar mass produced during the specific star formation burst, all as a function of the age of their parent stellar populations. Each of these indicators serves a different role, but in all cases we find that the HMXB formation efficiency increases as a function of time (following a burst of star formation) up to ~40-60Myr, and then gradually decreases. The formation efficiency peaks at ~30-40Myr with average rates of N(HMXB)/SFR=339_-83_^+78^(M_{sun}_/yr)^-1^, and N(HMXB)/M*=(8.74_-0.92_^+1.0^)x10^-6^M_{sun}_^-1^, in good agreement with previous estimates of the average formation efficiency in the broad ~20-60Myr age range.
