- ID:
- ivo://CDS.VizieR/J/ApJ/763/88
- Title:
- SDSS-II supernovae Ia cosmological analysis
- Short Name:
- J/ApJ/763/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the cosmological analysis of 752 photometrically classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the SN classification technique of Sako et al. (2011, Cat. J/ApJ/738/162), aided by host-galaxy redshifts (0.05<z<0.55). SuperNova ANAlysis simulations of our methodology estimate that we have an SN Ia classification efficiency of 70.8%, with only 3.9% contamination from core-collapse (non-Ia) SNe. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e.g., Malmquist bias) using simulations. When fitting to a flat {Lambda}CDM cosmological model, we find that our photometric sample alone gives {Omega}_m_=0.24^+0.07^_-0.05_ (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on {Omega}_m_ and {Omega}_{Lambda}_, comparable to those derived from the spectroscopically confirmed Three-year Supernova Legacy Survey (SNLS3). Using only our data, the statistics-only result favors an accelerating universe at 99.96% confidence. Assuming a constant wCDM cosmological model, and combining with H_0_, cosmic microwave background, and luminous red galaxy data, we obtain w=-0.96^+0.10^_-0.10_, {Omega}_m_=0.29^+0.02^_-0.02_, and {Omega}_k_=0.00^+0.03^_-0.02_ (statistical errors only), which is competitive with similar spectroscopically confirmed SNe Ia analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the SDSS-II SN sample (z<0.55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically classified SN Ia samples in improving cosmological constraints.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/136/2306
- Title:
- SDSS-II Supernova survey, 2005
- Short Name:
- J/AJ/136/2306
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ugriz light curves for 146 spectroscopically-confirmed or spectroscopically-probable Type Ia supernovae (SNe) from the 2005 season of the Sloan Digital Sky Survey-II Supernova (SN) survey. The light curves have been constructed using a photometric technique that we call scene modeling, which is described in detail here; the major feature is that SN brightnesses are extracted from a stack of images without spatial resampling or convolution of the image data. This procedure produces accurate photometry along with accurate estimates of the statistical uncertainty, and can be used to derive photometry taken with multiple telescopes. We discuss various tests of this technique that demonstrate its capabilities. We also describe the methodology used for the calibration of the photometry, and present calibrated magnitudes and fluxes for all of the spectroscopic SNe Ia from the 2005 season.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/1831
- Title:
- SDSS-IV eBOSS ELG UgrizW photometry
- Short Name:
- J/MNRAS/465/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two wide-field catalogues of photometrically selected emission line galaxies (ELGs) at z~=0.8 covering about 2800deg^2^ over the south galactic cap. The catalogues were obtained using a Fisher discriminant technique described in a companion paper. The two catalogues differ by the imaging used to define the Fisher discriminant: the first catalogue includes imaging from the Sloan Digital Sky Survey and the Wide-field InfraredSurvey Explorer, the second also includes information from the South Galactic Cap U-band Sky Survey. Containing respectively 560045 and 615601 objects, they represent the largest ELG catalogues available today and were designed for the ELG programme of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We study potential sources of systematic variation in the angular distribution of the selected ELGs due to fluctuations of the observational parameters. We model the influence of the observational parameters using a multivariate regression and implement a weighting scheme which allows effective removal of all of the systematic errors induced by the observational parameters. We show that fluctuations in the imaging zero-points of the photometric bands have minor impact on the angular distribution of objects in our catalogues. We compute the angular clustering of both catalogues and show that our weighting procedure effectively removes spurious clustering on large scales. We fit a model to the small-scale angular clustering, showing that the selections have similar biases of 1.35/Da(z) and 1.28/Da(z). Both catalogues are publicly available.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A121
- Title:
- SDSS-IV eBOSS emission-line galaxy pilot survey
- Short Name:
- J/A+A/592/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey IV extended Baryonic Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) will observe 195,000 emission-line galaxies (ELGs) to measure the Baryonic Acoustic Oscillation standard ruler (BAO) at redshift 0.9. To test different ELG selection algorithms, based on data from several imaging surveys, 9,000 spectra were observed with the SDSS spectrograph as a pilot survey. First, using visual inspection and redshift quality flags, we find that the automated spectroscopic redshifts assigned by the pipeline meet the quality requirements for a robust BAO measurement. Also, we show the correlations between sky emission, signal-to-noise ratio in the emission lines and redshift error. Then we provide a detailed description of each target selection algorithm tested and compare them with the requirements of the eBOSS experiment. As a result, we provide robust redshift distributions for the different target selection schemes tested. Finally, we infer two optimal target selection algorithms to be applied on DECam photometry that fulfill the eBOSS survey electronic efficiency requirements.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A97
- Title:
- SDSS-IV/SPIDERS X-ray PS Spectroscopic Catalog
- Short Name:
- J/A+A/636/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We look to provide a detailed description of the SPectroscopic IDentification of ERosita Sources (SPIDERS) survey, an SDSS-IV programme aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. We describe the SPIDERS X-ray Point Source Spectroscopic Catalogue, considering its store of 11092 observed spectra drawn from a parent sample of 14759 ROSAT and XMM sources over an area of 5129deg^2^ covered in SDSS-IV by the eBOSS survey. This programme represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10970 (98.9%) of the observed objects are classified and 10849 (97.8%) have secure redshifts. The majority of the spectra (10070 objects) are active galactic nuclei (AGN), 522 are cluster galaxies, and 294 are stars. The observed AGN redshift distribution is in good agreement with simulations based on empirical models for AGN activation and duty cycle. Forming composite spectra of type 1 AGN as a function of the mass and accretion rate of their black holes reveals systematic differences in the H-beta emission line profiles. This study paves the way for systematic spectroscopic observations of sources that are potentially to be discovered in the upcoming eROSITA survey over a large section of the sky.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A165
- Title:
- SDSS J1339+1310 light curves and spectra
- Short Name:
- J/A+A/646/A165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the accretion disc structure in the doubly imaged lensed quasar SDSS J1339+1310 using r-band light curves and UV-visible to near-IR spectra from the first 11 observational seasons after its discovery. The 2009-2019 light curves displayed pronounced microlensing variations on different timescales, and this microlensing signal permitted us to constrain the half-light radius of the 1930{AA} continuum-emitting region. Assuming an accretion disc with an axis inclined at 60{deg} to the line of sight, we obtained log(r_1/2_/cm)=15.4_-0.4+^+0.93%. We also estimated the central black hole mass from spectroscopic data. The width of the CIV, MgII, and H{beta} emission lines, and the continuum luminosity at 1350, 3000, and 5100{AA}, led to log(M_BH_/M_{sun}_)=8.6+/-0.4. Thus, hot gas responsible for the 1930{AA} continuum emission is likely orbiting a 4.0x10^8^M_{sun}_ black hole at an r_1/2_ of only a few tens of Schwarzschild radii.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/8
- Title:
- SDSS J120414.37+351800.5 quasar optical photometry
- Short Name:
- J/ApJ/859/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A small fraction of quasars show an unusually high nitrogen-to-carbon ratio (N/C) in their spectra. These "nitrogen-rich" (N-rich) quasars are a long-standing puzzle because their interstellar medium implies stellar populations with abnormally high metallicities. It has recently been proposed that N-rich quasars may result from tidal disruption events (TDEs) of stars by supermassive black holes. The rapid enhancement of nitrogen and the depletion of carbon due to the carbon-nitrogen-oxygen cycle in supersolar mass stars could naturally produce high N/C. However, the TDE hypothesis predicts that the N/C should change with time, which has never hitherto been observed. Here we report the discovery of the first N-rich quasar with rapid N/C variability that could be caused by a TDE. Two spectra separated by 1.7yrs (rest-frame) show that the NIII]{lambda}1750/CIII]{lambda}1909 intensity ratio decayed by ~86%+/-14% (1{sigma}). Optical (rest-frame UV) light-curve and X-ray observations are qualitatively consistent with the TDE hypothesis; though, the time baseline falls short of a definitive proof. Putting the single-object discovery into context, statistical analyses of the ~80 known N-rich quasars with high-quality archival spectra show evidence (at a 5{sigma} significance level) of a decrease in N/C on timescales of >1 year (rest-frame) and a constant level of ionization (indicated by the CIII]{lambda}1909/CIV{lambda}1549 intensity ratio). If confirmed, our results demonstrate the method of identifying TDE candidates in quasars via abundance ratio variability, opening a new window of TDE observations at high redshift (z>2) with upcoming large-scale time-domain spectroscopic surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A77
- Title:
- SDSS J1339+1310 spectra and light curves
- Short Name:
- J/A+A/596/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We spectroscopically re-observed the gravitational lens system SDSS J1339+1310 using OSIRIS on the GTC. We also monitored the r-band variability of the two quasar images (A and B) with the LT over 143 epochs in the period 2009-2016. These new data in both the wavelength and time domains have confirmed that the system is an unusual microlensing factory. The CIV emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A,{mu}_BA_, reaches a value of 1.4 (~0.4mag) for its core. Moreover, the B image shows a red wing enhancement of CIV flux (relative to A), and {mu}_BA_=2 (0.75mag) for the CIV broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of {mu}_BA_, which roughly varies from ~5 (1.75mag) at 7000{AA} to ~6 (1.95mag) at 4000{AA}. We also detect significant microlensing variability in the r band, and this includes a number of microlensing events on timescales of 50-100d. Fortunately, the presence of an intrinsic 0.7 mag dip in the light curves of A and B, permitted us to measure the time delay between both quasar images. This delay is {Delta}t_AB_=47^+5^_-6_d (1{sigma} confidence interval; A is leading), in good agreement with predictions of lens models.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A77
- Title:
- SDSS J080434.20+510349.2 spectra and photometry
- Short Name:
- J/A+A/549/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study of SDSS J080434.20+510349.2 (SDSS0804) is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A qualitative geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7+/-0.1 from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07mag amplitude and a 42.48min periodicity, which is half of the orbital period of the system. In September 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-hump-shape, but with a significantly smaller (~0.01mag) amplitude. Other types of variability like a "mini-outburst" or SDSS1238-like features were not detected. Doppler tomograms, obtained from spectroscopic data during the same period of time, show a large accretion disk with uneven brightness, implying the presence of spiral waves. We constructed a geometric model of a bounce-back system containing two spiral density waves in the outer annuli of the disk to reproduce the observed light curves. The Doppler tomograms and the double-hump-shape light curves in quiescence can be explained by a model system containing a massive >=0.7M_{sun}_ white dwarf with a surface temperature of ~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli spirals. According to this model, the accretion disk should be large, extending to the 2:1 resonance radius, and cool ~2500K. The inner parts of the disk should be optically thin in the continuum or totally void.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/134
- Title:
- SDSS low-metallicity blue compact dwarf galaxies
- Short Name:
- J/ApJ/863/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3m Lick Observatory and 10m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12+log(O/H)<=7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12+log(O/H)~7.20.
