- ID:
- ivo://CDS.VizieR/J/ApJ/778/98
- Title:
- Cross-correlation of SDSS QSOs and BOSS galaxies
- Short Name:
- J/ApJ/778/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 quasars and 349608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey (BOSS) at 0.3<z<0.9. The CCF can be reasonably well fit by a power-law model {xi}_QG_(r)=(r/r_0_)^-{gamma}^ on projected scales of r_p_=2-25h^-1^Mpc with r_0_=6.61+/-0.25h^-1^Mpc and {gamma}=1.69+/-0.07. We estimate a quasar linear bias of b_Q_=1.38+/-0.10 at <z>{=}0.53 from the CCF measurements, which corresponds to a characteristic host halo mass of ~4x10^12^h^-1^M_{sun}_, compared with a ~10^13^h^-1^M_{sun}_ characteristic host halo mass for CMASS galaxies. Based on the clustering measurements, most quasars at {overline}{z}~0.5 are not the descendants of their higher luminosity counterparts at higher redshift, which would have evolved into more massive and more biased systems at low redshift. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db_Q_/dlogL=0.20+/-0.34 or 0.11+/-0.32 (depending on different luminosity divisions) for quasar luminosities -23.5>M_i_(z=2)>-25.5, implying a weak luminosity dependence of clustering for luminous quasars at {overline}{z}~0.5. We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations and ambiguities in modeling the distribution of quasars with the standard HOD approach.
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882. CS Cha B spectrum
- ID:
- ivo://CDS.VizieR/J/A+A/640/L12
- Title:
- CS Cha B spectrum
- Short Name:
- J/A+A/640/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct imaging provides a steady flow of newly discovered giant planets and brown dwarf companions. These multi-object systems can provide information about the formation of low-mass companions in wide orbits and/or speculate about possible migration scenarios. The accurate classification of the companions is crucial for testing formation pathways. In this work we characterize further the recently discovered candidate for a planetary-mass companion CS Cha b and determine if it is still accreting. MUSE is a 4-laser-adaptive-optics-assisted medium-resolution integral-field spectrograph in the optical part of the spectrum. We observed the CS Cha system to obtain the first spectrum of CS Cha b. The companion is characterized by modelling both the spectrum from 6300{AA}, to 9300{AA}, and the photometry using archival data from the visible to the near-infrared. We find evidence of accretion and outflow signatures in H{alpha} and OI emission. The atmospheric models with the highest likelihood indicate an effective temperature of 3450+/-50K with a logg of 3.6+/-0.5dex. Based on evolutionary models, we find that the majority of the object is obscured. We determine the mass of the faint companion with several methods to be between 0.07 Msun and 0.71M_{sun}_ with an accretion rate of dM/dt=4x10^-11^+/-0.4x10^-11^M_{sun}_/yr. Our results show that CS Cha B is most likely a mid M-type star that is obscured by a highly inclined disk, which has led to its previous classification by broadband NIR photometry as a planetary-mass companion. This shows that it is important and necessary to observe over a broad spectral range to constrain the nature of faint companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/776/L20
- Title:
- C/2012 S1 (comet ISON) R photometry
- Short Name:
- J/ApJ/776/L20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report photometric observations for comet C/2012 S1 (ISON) obtained during the time period immediately after discovery (r=6.28AU) until it moved into solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8m telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from the CARA network. Additional pre-discovery data from the Pan STARRS1 survey extends the light curve back to 2011 September 30 (r=9.4AU). The images showed a similar tail morphology due to small micron sized particles throughout 2013. Observations at submillimeter wavelengths using the James Clerk Maxwell Telescope on 15 nights between 2013 March 9 (r=4.52AU) and June 16 (r=3.35AU) were used to search for CO and HCN rotation lines. No gas was detected, with upper limits for CO ranging between 3.5-4.5x10^27^molecules/s. Combined with published water production rate estimates we have generated ice sublimation models consistent with the photometric light curve. The inbound light curve is likely controlled by sublimation of CO_2_. At these distances water is not a strong contributor to the outgassing. We also infer that there was a long slow outburst of activity beginning in late 2011 peaking in mid-2013 January (r~5AU) at which point the activity decreased again through 2013 June. We suggest that this outburst was driven by CO injecting large water ice grains into the coma. Observations as the comet came out of solar conjunction seem to confirm our models.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/140
- Title:
- CSP-II: sp. obs. of the 03fg-like SN Ia LSQ14fmg
- Short Name:
- J/ApJ/900/140
- Date:
- 02 Feb 2022 11:26:50
- Publisher:
- CDS
- Description:
- The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SNIa, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than M_V_=-19mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than -20.5mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized 56Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.
- ID:
- ivo://CDS.VizieR/J/A+A/436/91
- Title:
- C star population in outer disk of M31
- Short Name:
- J/A+A/436/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFHT Megacam camera to survey ~1{deg}^2^ of the southern outer disc of M31, a region which includes the area where Battinelli et al. (2003, Cat. <J/AJ/125/1298>) have identified nearly one thousand C stars. In the outer M31 region not previously surveyed, we identify 361 new C star candidates, having similar photometric properties to the known ones, and confirm the slight decrease in the luminosity of C stars with galactocentric distances. We show that the Sloan g', r', i' filters are a viable approach, comparable to (CN-TiO), to identify C stars. We find that the (g'-r') colours of cool C stars can be so red that prohibitively long g' exposures are needed to acquire faint extragalactic C stars. This makes the Sloan filters a less promising approach to extend a C star survey to several Mpc. Our uniform large field survey detects the edge of M31 disk at ~35kpc. The intermediate-age population, represented by C stars, extends further to ~40kpc.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1298
- Title:
- C star population in outer disk of M31
- Short Name:
- J/AJ/125/1298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFH12K mosaic to identify carbon stars, using the R, I, CN, and TiO photometric technique, in a 2240 arcmin2 area, ranging from 17 to 30kpc of the southwest disk of M31, barely reaching the edge of the observed H I disk. We found 945 C stars with <I_0_>=19.94mag and {sigma}=0.47. The surface density of C stars along the major axis of M31 follows an exponential profile with a scale length of 4.85+/-0.35kpc, in agreement with adopted values for the scale length of the disk population. Our survey partially overlaps with the recently discovered G1 density enhancement by Ferguson et al. We confirm that no AGB star excess is detectable in the surveyed part of the clump. The C/M ratio, along the major axis, is derived over a distance range of 7kpc. The strong C/M gradient seen contrasts with results of previous studies of the C stars in M31.
887. C stars in IC 1613
- ID:
- ivo://CDS.VizieR/J/AJ/119/2780
- Title:
- C stars in IC 1613
- Short Name:
- J/AJ/119/2780
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a multifilter survey of the whole Magellanic-type galaxy IC 1613. Narrowband CN and TiO filters are used to identify carbon stars among red giants. We have identified 195 carbon stars, extending up to 15' from the center of the galaxy. We present well-calibrated R and I magnitudes for all stars. The large field surveyed allows a reliable foreground estimate of M stars, leading to a C/M ratio of 0.64, when giants as early as M0 are counted. Analysis of the photometric properties of the C star population reveals a narrow M_I_ distribution with a mean M_I_ of -4.69mag, with a dispersion of +/-0.28. IC 1613 has, for its absolute magnitude, a normal number of C stars.
- ID:
- ivo://CDS.VizieR/J/AJ/120/1801
- Title:
- C stars in Pegasus, DDO 210 and Tucana
- Short Name:
- J/AJ/120/1801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the latest results of our ongoing four-filter photometric survey of C stars in Local Group dwarf irregular galaxies. Observations of the two low-luminosity dwarf irregular galaxies, Pegasus and DDO 210, revealed 40 and three C stars, respectively, assuming that the reddening of Pegasus is negligible. No C stars were identified in Tucana. Our observations permit the estimation of the color-magnitude diagram contamination by foreground M dwarfs thus yielding reliable C/M ratios. Our R and I photometry of the C stars cannot be used to solve the extinction controversy toward Pegasus. The three C stars in DDO 210 are quite bright when compared with C star populations in other dwarf galaxies. A larger, fainter population in that galaxy seems improbable, however. The statistics of C stars currently on hand for dwarf galaxies show a well-defined trend with the absolute magnitude of dwarf galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2020
- Title:
- CTIO and WFPC2 photometry in NGC 6822
- Short Name:
- J/AJ/121/2020
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the massive star population of NGC 6822 with ground-based UBV photometry covering the whole of the galaxy and HST WFPC2 photometry with filters F255W, F336W, F439W, and F555W of two fields containing very rich and crowded OB associations. The four-band WFPC2 photometry is used to derive Teff and E(B-V). H-R diagrams are constructed for the OB associations included in our fields. These show that 10Myr old populations are present in OB 9 and OB 6, while more recent star formation have occurred in OB 8, OB 13, OB 15, and OB 7. Two particularly interesting H II regions, Hubble V and Hubble X, are included in our fields. The luminous massive stars that power these bright H II regions (H{alpha} luminosity several times that of the Orion nebula), could be resolved even in their dense cores thanks to the HST spatial resolution. Our data reveal very young (a few million years), apparently coeval populations, with several massive star candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/112
- Title:
- CTIO/DECam LCs for Galactic bulge variable stars
- Short Name:
- J/ApJ/892/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, p_f_^(dm|dt)^, and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha+ (2019, J/ApJ/874/30) in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.
