- ID:
- ivo://CDS.VizieR/J/A+A/584/A26
- Title:
- Cosmography of OB stars in the solar neighbourhood
- Short Name:
- J/A+A/584/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a 3D map of the spatial density of OB stars within 500pc from the Sun using the Hipparcos catalogue and find three large-scale stream-like structures that allow a new view on the solar neighbourhood. The spatial coherence of these blue streams and the monotonic age sequence over hundreds of parsecs suggest that they are made of young stars, similar to the young streams that are conspicuous in nearby spiral galaxies. The three streams are 1) the Scorpius to Canis Majoris stream, covering 350pc and 65Myr of star formation history; 2) the Vela stream, encompassing at least 150pc and 25Myr of star formation history; and 3) the Orion stream, including not only the well-known Orion OB1abcd associations, but also a large previously unreported foreground stellar group lying only 200pc from the Sun. The map also reveals a remarkable and previously unknown nearby OB association, between the Orion stream and the Taurus molecular clouds, which might be responsible for the observed structure and star formation activity in this cloud complex. This new association also appears to be the birthplace of Betelgeuse, as indicated by the proximity and velocity of the red giant. If this is confirmed, it would solve the long-standing puzzle of the origin of Betelgeuse. The well-known nearby star-forming low-mass clouds, including the nearby T and R associations Lupus, Cha, Oph, CrA, Taurus, Vela R1, and various low-mass cometary clouds in Vela and Orion, appear in this new view of the local neighbourhood to be secondary star formation episodes that most likely were triggered by the feedback from the massive stars in the streams. We also recover well-known star clusters of various ages that are currently cruising through the solar neighbourhood. Finally, we find no evidence of an elliptical structure such as the Gould belt, a structure we suggest is a 2D projection effect, and not a physical ring.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/172/523
- Title:
- COSMOS field Ly{alpha} emitters at z~5.7
- Short Name:
- J/ApJS/172/523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a narrow-band optical survey of a contiguous area of 1.95deg^2^, covered by the Cosmic Evolution Survey (COSMOS). Both optical narrow-band ({lambda}c=8150{AA} and {delta}{lambda}=120{AA}) and broad-band (B, V, g', r', i', and z') imaging observations were performed with the Subaru prime-focus camera, Suprime-Cam on the Subaru Telescope. We provide the largest contiguous narrow-band survey, targeting Ly{alpha} emitters (LAEs) at z~5.7. We find a total of 119 LAE candidates at z~5.7. Over the wide-area covered by this survey, we find no strong evidence for large-scale clustering of LAEs. We estimate a star formation rate (SFR) density of ~7x10-4M_{sun}_/yr/Mpc^3^ for LAEs at z~5.7 and compare it with previous measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/68
- Title:
- COSMOS lens candidates with LensFlow
- Short Name:
- J/ApJ/856/68
- Date:
- 08 Mar 2022 14:20:03
- Publisher:
- CDS
- Description:
- In this work, we present our machine learning classification algorithm for identifying strong gravitational lenses from wide-area surveys using convolutional neural networks; LensFlow. We train and test the algorithm using a wide variety of strong gravitational lens configurations from simulations of lensing events. Images are processed through multiple convolutional layers that extract feature maps necessary to assign a lens probability to each image. LensFlow provides a ranking scheme for all sources that could be used to identify potential gravitational lens candidates by significantly reducing the number of images that have to be visually inspected. We apply our algorithm to the HST/ACS i-band observations of the COSMOS field and present our sample of identified lensing candidates. The developed machine learning algorithm is more computationally efficient and complimentary to classical lens identification algorithms and is ideal for discovering such events across wide areas from current and future surveys such as LSST and WFIRST.
- ID:
- ivo://CDS.VizieR/II/284
- Title:
- COSMOS Multi-Wavelength Photometry Catalog
- Short Name:
- II/284
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging data and photometry for the COSMOS survey in 15 photometric bands between 0.3 and 2.4m. These include data taken on the Subaru 8.3m telescope, the KPNO and CTIO 4m telescopes, and the CFHT 3.6m telescope. Special techniques are used to ensure that the relative photometric calibration is better than 1% across the field of view. The absolute photometric accuracy from standard-star measurements is found to be 6%. The absolute calibration is corrected using galaxy spectra, providing colors accurate to 2% or better. Stellar and galaxy colors and counts agree well with the expected values. Finally, as the first step in the scientific analysis of these data we construct panchromatic number counts which confirm that both the geometry of the universe and the galaxy population are evolving.
- ID:
- ivo://CDS.VizieR/J/ApJS/206/8
- Title:
- COSMOS/UltraVISTA Ks-selected catalogs v4.1
- Short Name:
- J/ApJS/206/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog covering 1.62deg^2^ of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24{mu}m including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA K_s_ band imaging that reaches a depth of K_s,tot_=23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z_phot_) for all galaxies computed with the EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z~1.5 the z_phot_ are accurate to {Delta}z/(1+z)=0.013, with a catastrophic outlier fraction of only 1.6%. The z_phot_ also show good agreement with the z_phot_ from the NEWFIRM Medium Band Survey out to z~3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U-V and V-J colors, L_2800_ and L_IR_. The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z~2. Star-forming galaxies also obey a star-forming "main sequence" out to z~2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA K_s_-selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z~3-4.
876. COSMOS 70um sources
- ID:
- ivo://CDS.VizieR/J/ApJ/709/572
- Title:
- COSMOS 70um sources
- Short Name:
- J/ApJ/709/572
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large robust sample of 1503 reliable and unconfused 70um selected sources from the multiwavelength data set of the Cosmic Evolution Survey. Using the Spitzer IRAC and MIPS photometry, we estimate the total infrared (IR) luminosity, LIR (8-1000um), by finding the best-fit template from several different template libraries. The long-wavelength 70 and 160um data allow us to obtain a reliable estimate of LIR, accurate to within 0.2 and 0.05dex, respectively. The 70um data point enables a significant improvement over the luminosity estimates possible with only a 24um detection. The full sample spans a wide range in IR luminosity, LIR~10^8^-10^14^L_{sun}_, with a median luminosity of 10^11.4^L_{sun}_. We identify a total of 687 luminous, 303 ultraluminous, and 31 hyperluminous infrared galaxies (LIRGs, ULIRGs, and HyLIRGs) over the redshift range 0.01<z<3.5 with a median redshift of 0.5. Presented here are the full spectral energy distributions (SEDs) for each of the sources compiled from the extensive multiwavelength data set from the ultraviolet (UV) to the far-infrared. A catalog of the general properties of the sample (including the photometry, redshifts, and LIR) is included with this paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/L16
- Title:
- Counterpart of GW170817. I. DECam obs.
- Short Name:
- J/ApJ/848/L16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70deg^2^ in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4hr post-merger we detected a bright optical transient located 10.6" from the nucleus of NGC 4993 at redshift z=0.0098, consistent (for H_0_=70km/s/Mpc) with the distance of 40+/-8Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of i=17.3 and z=17.4, and thus an absolute magnitude of Mi=-15.7, in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/203/15
- Title:
- Counterparts to 1.4GHz sources in ECDF-S
- Short Name:
- J/ApJS/203/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 883 sources detected in a deep Very Large Array survey at 1.4GHz in the Extended Chandra Deep Field South. This paper focuses on the identification of their optical and infrared (IR) counterparts. We use a likelihood-ratio technique that is particularly useful when dealing with deep optical images to minimize the number of spurious associations. We find a reliable counterpart for 95% of our radio sources. Most of the counterparts (74%) are detected at optical wavelengths, but there is a significant fraction (21%) that are only detectable in the IR. Combining newly acquired optical spectra with data from the literature, we are able to assign a redshift to 81% of the identified radio sources (37% spectroscopic). We also investigate the X-ray properties of the radio sources using the Chandra 4Ms and 250ks observations. In particular, we use a stacking technique to derive the average properties of radio objects undetected in the Chandra images. The results of our analysis are collected in a new catalog containing the position of the optical/IR counterpart, the redshift information, and the X-ray fluxes. It is the deepest multi-wavelength catalog of radio sources, which will be used for future study of this galaxy population.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1602
- Title:
- Cousins RI photometry in IC 348
- Short Name:
- J/AJ/127/1602
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extremely young cluster IC 348 has been monitored photometrically over five observing seasons from 1998 December 10 to 2003 March 26 in Cousins I with a 0.6m telescope at Van Vleck Observatory. Twenty-eight periodic variables and 16 irregular variables have been identified. The variability study is most sensitive for stars with I<14.3mag; at that brightness level, we find that 24 of the 27 known pre-main-sequence (PMS) cluster members in the monitored field are variables, illustrating the value of photometric monitoring for identifying PMS cluster members. Among this brighter sample, 14 of the 16 known K or M-type weak-line T Tauri stars (WTTS) were found to be periodic variables, while all five of the known classical T Tauri stars (CTTS) were found to be irregular variables. In the full sample, which includes 150 stars with I as faint as 18, we find that 40% of the 63 WTTS are detected as variables, nearly all of them periodic, while 55% of the 20 CTTS are also detected as variable, with none of them periodic.
- ID:
- ivo://CDS.VizieR/J/MNRAS/376/580
- Title:
- Cousins RI photometry of NGC 2169
- Short Name:
- J/MNRAS/376/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used Cousins RI CCD photometry from the Isaac Newton telescope and intermediate-resolution spectroscopy from the Gemini North telescope to identify and characterize low-mass (0.15<M/M_{sun}_<1.3) pre-main-sequence stars in the young open cluster NGC 2169. Isochrone fitting to the high- and low-mass populations yields an intrinsic distance modulus of 10.13^+0.06^_-0.09_mag and a model-dependent age of 9+/-2Myr. Compared to the nearby, kinematically defined groups of a similar age, NGC 2169 has a large low-mass population which potentially offers a more precise statistical investigation of several aspects of star formation and early stellar evolution. By modelling the distribution of low-mass stars in the IC versus RC IC diagram, we find that any age spread among cluster members has a Gaussian full width at half-maximum (FWHM) 2.5Myr. A young age and a small age spread (<10Myr) are supported by the lack of significant lithium depletion in the vast majority of cluster members. There is no clear evidence for accretion or warm circumstellar dust in the low-mass members of NGC 2169, bolstering the idea that strong accretion has ceased and inner discs have dispersed in almost all low-mass stars by ages of 10Myr.
