- ID:
- ivo://CDS.VizieR/J/ApJ/819/24
- Title:
- z>4.5 QSOs with SDSS and WISE. I. Opt. spectra
- Short Name:
- J/ApJ/819/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-redshift quasars are important tracers of structure and evolution in the early universe. However, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. High-redshift quasar surveys based on only optical colors suffer from incompleteness and low identification efficiency, especially at z>~4.5. We have developed a new method to select 4.7<~z>~5.4 quasars with both high efficiency and completeness by combining optical and mid-IR Wide-field Infrared Survey Explorer (WISE) photometric data, and are conducting a luminous z~5 quasar survey in the whole Sloan Digital Sky Survey (SDSS) footprint. We have spectroscopically observed 99 out of 110 candidates with z-band magnitudes brighter than 19.5, and 64 (64.6%) of them are quasars with redshifts of 4.4<~z<~5.5 and absolute magnitudes of -29<~M_1450_<~-26.4. In addition, we also observed 14 fainter candidates selected with the same criteria and identified 8 (57.1%) of them as quasars with 4.7<z<5.4. Among 72 newly identified quasars, 12 of them are at 5.2<z<5.7, which leads to an increase of ~36% of the number of known quasars at this redshift range. More importantly, our identifications doubled the number of quasars with M_1450_<-27.5 at z>4.5, which will set strong constraints on the bright end of the quasar luminosity function. We also expand our method to select quasars at z>~5.7. In this paper we report the discovery of four new luminous z>~5.7 quasars based on SDSS-WISE selection.
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- ID:
- ivo://CDS.VizieR/J/AJ/155/131
- Title:
- z~5 quasar luminosity function from the CFHTLS
- Short Name:
- J/AJ/155/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a spectroscopic survey of z~5 quasars in the CFHT Legacy Survey (Cat. II/317). Using both optical color selection and a likelihood method, we select 97 candidates over an area of 105 deg^2^ to a limit of i_AB_<23.2, and 7 candidates in the range 23.2<i_AB_<23.7 over an area of 18.5 deg^2^. Spectroscopic observations for 43 candidates were obtained with Gemini, MMT, and Large Binocular Telescope, of which 37 are z>4 quasars. This sample extends measurements of the quasar luminosity function ~1.5 mag fainter than our previous work in Sloan Digital Sky Survey Stripe 82. The resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. We perform a detailed examination of our survey completeness, particularly the impact of the Ly{alpha} emission assumed in our quasar spectral models, and find hints that the observed Ly{alpha} emission from faint z~5 quasars is weaker than for z~3 quasars at a similar luminosity. Our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z=5.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/152
- Title:
- ZTF early observations of Type Ia SNe. I. LCs
- Short Name:
- J/ApJ/886/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Early-time observations of Type Ia supernovae (SNe Ia) are essential to constrain the properties of their progenitors. In this paper, we present high-quality light curves of 127 SNe Ia discovered by the Zwicky Transient Facility (ZTF) in 2018. We describe our method to perform forced point-spread function photometry, which can be applied to other types of extragalactic transients. With a planned cadence of six observations per night (three g + three r), all of the 127 SNe Ia are detected in both g and r bands more than 10 days (in the rest frame) prior to the epoch of g-band maximum light. The redshifts of these objects range from z=0.0181 to 0.165; the median redshift is 0.074. Among the 127 SNe, 50 are detected at least 14 days prior to maximum light (in the rest frame), with a subset of nine objects being detected more than 17 days before g-band peak. This is the largest sample of young SNe Ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. We discuss six peculiar events in this sample: one 02cx-like event ZTF18abclfee (SN2018crl), one Ia-CSM SN ZTF18aaykjei (SN2018cxk), and four objects with possible super-Chandrasekhar mass progenitors: ZTF18abhpgje (SN2018eul), ZTF18abdpvnd (SN2018dvf), ZTF18aawpcel (SN2018cir), and ZTF18abddmrf (SN2018dsx).
- ID:
- ivo://CDS.VizieR/J/AJ/162/63
- Title:
- ZTF light curve of 51 stars in 12 globular clusters
- Short Name:
- J/AJ/162/63
- Date:
- 21 Mar 2022 11:55:52
- Publisher:
- CDS
- Description:
- In this work, we aimed to derive the gri-band period-luminosity (PL) and period-luminosity-color (PLC) relations for late-type contact binaries, for the first time, located in globular clusters, using the homogeneous light curves collected by the Zwicky Transient Factory (ZTF). We started with 79 contact binaries in 15 globular clusters, and retained 30 contact binaries in 10 globular clusters that have adequate numbers of data points in the ZTF light curves and are unaffected by blending. Magnitudes at mean and maximum light of these contact binaries were determined using a fourth-order Fourier expansion, while extinction corrections were done using the Bayerstar2019 3D reddening map together with adopting the homogeneous distances to their host globular clusters. After removing early-type and "anomaly" contact binaries, our derived gri-band PL and period-Wesenheit (PW) relations exhibited a much larger dispersion with large errors on the fitted coefficients. Nevertheless, the gr-band PL and PW relations based on this small sample of contact binaries in globular clusters were consistent with those based on a larger sample of nearby contact binaries. Good agreements of the PL and PW relations suggested both samples of contact binaries in the local Solar neighborhood and in the distant globular clusters can be combined and used to derive and calibrate the PL, PW, and PLC relations. The final derived gr-band PL, PW, and PLC relations were much improved over those based on the limited sample of contact binaries in the globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/L2
- Title:
- ZTF observations of FRB 180916.J0158+65
- Short Name:
- J/ApJ/896/L2
- Date:
- 07 Dec 2021
- Publisher:
- CDS
- Description:
- The discovery rate of fast radio bursts (FRBs) is increasing dramatically thanks to new radio facilities. Meanwhile, wide-field instruments such as the 47deg^2^ Zwicky Transient Facility (ZTF) survey the optical sky to study transient and variable sources. We present serendipitous ZTF observations of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) repeating source FRB180916.J0158+65 that was localized to a spiral galaxy 149Mpc away and is the first FRB suggesting periodic modulation in its activity. While 147 ZTF exposures corresponded to expected high-activity periods of this FRB, no single ZTF exposure was at the same time as a CHIME detection. No >3{sigma} optical source was found at the FRB location in 683 ZTF exposures, totaling 5.69hr of integration time. We combined ZTF upper limits and expected repetitions from FRB 180916.J0158+65 in a statistical framework using a Weibull distribution, agnostic of periodic modulation priors. The analysis yielded a constraint on the ratio between the optical and radio fluences of {eta}<~200, corresponding to an optical energy E_opt_<~3x10^46^erg for a fiducial 10Jy.ms FRB (90% confidence). A deeper (but less statistically robust) constraint of {eta}<~3 can be placed assuming a rate of r(>5Jy.ms)=1hr^-1^ and 1.2+/-1.1 FRB occurring during exposures taken in high-activity windows. The constraint can be improved with shorter per-image exposures and longer integration time, or observing FRBs at higher Galactic latitudes. This work demonstrated how current surveys can statistically constrain multiwavelength counterparts to FRBs even without deliberately scheduled simultaneous radio observation.
- ID:
- ivo://CDS.VizieR/J/ApJ/895/32
- Title:
- Zwicky Transient Facility BTS. I.
- Short Name:
- J/ApJ/895/32
- Date:
- 16 Mar 2022 00:25:08
- Publisher:
- CDS
- Description:
- The Zwicky Transient Facility (ZTF) is performing a three-day cadence survey of the visible northern sky (~3{pi}) with newly found transient candidates announced via public alerts. The ZTF Bright Transient Survey (BTS) is a large spectroscopic campaign to complement the photometric survey. BTS endeavors to spectroscopically classify all extragalactic transients with m_peak_<~18.5mag in either the g_ZTF_ or r_ZTF_ filters, and publicly announce said classifications. BTS discoveries are predominantly supernovae (SNe), making this the largest flux-limited SN survey to date. Here we present a catalog of 761 SNe, classified during the first nine months of ZTF (2018 April 1-2018 December 31). We report BTS SN redshifts from SN template matching and spectroscopic host-galaxy redshifts when available. We analyze the redshift completeness of local galaxy catalogs, the redshift completeness fraction (RCF; the ratio of SN host galaxies with known spectroscopic redshift prior to SN discovery to the total number of SN hosts). Of the 512 host galaxies with SNe Ia, 227 had previously known spectroscopic redshifts, yielding an RCF estimate of 44%{+/-}4%. The RCF decreases with increasing distance and decreasing galaxy luminosity (for z<0.05, or ~200Mpc, RCF~0.6). Prospects for dramatically increasing the RCF are limited to new multifiber spectroscopic instruments or wide-field narrowband surveys. Existing galaxy redshift catalogs are only ~50% complete at r~16.9mag. Pushing this limit several magnitudes deeper will pay huge dividends when searching for electromagnetic counterparts to gravitational wave events or sources of ultra-high-energy cosmic rays or neutrinos.
- ID:
- ivo://CDS.VizieR/J/AJ/160/252
- Title:
- ZZ Ceti white dwarfs and candidates in Gaia survey
- Short Name:
- J/AJ/160/252
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- The Gaia satellite recently released parallax measurements for ~260000 high-confidence white dwarf candidates, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and u-band photometry, we measured the effective temperature and stellar mass for all white dwarfs in the Northern Hemisphere within 100pc of the Sun, and identified a sample of ZZ-Ceti white dwarf candidates within the so-called instability strip. We acquired high-speed photometric observations for 90 candidates using the PESTO camera attached to the 1.6m telescope at the Mont-Megantic Observatory. We report the discovery of 38 new ZZ-Ceti stars, including two very rare ultramassive pulsators. We also identified five possibly variable stars within the strip, in addition to 47 objects that do not appear to show any photometric variability. However, several of those could be variable with an amplitude below our detection threshold, or could be located outside the instability strip due to errors in their photometric parameters. In the light of our results, we explore the trends of the dominant period and amplitude in the M--Teff plane, and briefly discuss the question of the purity of the ZZ-Ceti instability strip (i.e., a region devoid of non-variable stars).
