- ID:
- ivo://CDS.VizieR/J/AJ/146/100
- Title:
- New 2.2<z<3.5 quasars from SDSS and UKIDSS
- Short Name:
- J/AJ/146/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The identification of quasars at intermediate redshifts (2.2<z<3.5) has been inefficient in most previous quasar surveys since the optical colors of quasars are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this difficulty. Our recent study also proposed to use optical/near-IR colors for selecting z<4 quasars. To verify the effectiveness of this method, we selected a list of 105 unidentified bright targets with i<=18.5 from the quasar candidates of SDSS DR6 with both SDSS ugriz optical and UKIDSS YJHK near-IR photometric data, which satisfy our proposed Y-K/g-z criterion and have photometric redshifts between 2.2 and 3.5 estimated from the nine-band SDSS-UKIDSS data. We observed 43 targets with the BFOSC instrument on the 2.16m optical telescope at Xinglong station of the National Astronomical Observatory of China in the spring of 2012. We spectroscopically identified 36 targets as quasars with redshifts between 2.1 and 3.4. The high success rate of discovering these quasars in the SDSS spectroscopic surveyed area further demonstrates the robustness of both the Y-K/g-z selection criterion and the photometric redshift estimation technique. We also used the above criterion to investigate the possible stellar contamination rate among the quasar candidates of SDSS DR6, and found that the rate is much higher when selecting 3<z<3.5 quasar candidates than when selecting lower redshift candidates (z<2.2). The significant improvement in the photometric redshift estimation when using the nine-band SDSS-UKIDSS data over the five-band SDSS data is demonstrated and a catalog of 7727 unidentified quasar candidates in SDSS DR6 selected with optical/near-IR colors and having photometric redshifts between 2.2 and 3.5 is provided. We also tested the Y-K/g-z selection criterion with the recently released SDSS-III/DR9 quasar catalog and found that 96.2% of 17999 DR9 quasars with UKIDSS Y- and K-band data satisfy our criterion. With some available samples of red quasars and type II quasars, we find that 88% and 96.5% of these objects can be selected by the Y-K/g-z criterion, respectively, which supports our claim that using the Y-K/g-z criterion efficiently selects both unobscured and obscured quasars. We discuss the implications of our results on the ongoing and upcoming large optical and near-IR sky surveys.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/130/1502
- Title:
- NGC 5846 group: photometry and spectroscopy
- Short Name:
- J/AJ/130/1502
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a photometric and spectroscopic survey of a 10{deg}^2^ region surrounding the nearby NGC 5846 group of galaxies, using the Canada-France-Hawaii and Keck I telescopes to study the population of dwarf galaxies as faint as M_R_=-10. Candidates are identified on the basis of quantitative surface brightness and qualitative morphological criteria. Spectroscopic follow up and a spatial correlation analysis provide the basis for affirming group memberships. Altogether, 324 candidates are identified, and 83 have spectroscopic membership confirmation.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/44
- Title:
- NGVS. XX. RedGOLD background galaxy clusters
- Short Name:
- J/ApJ/829/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We build a background cluster candidate catalog from the Next Generation Virgo Cluster Survey (NGVS) using our detection algorithm RedGOLD. The NGVS covers 104deg^2^ of the Virgo cluster in the u^*^,g,r,i,z-bandpasses to a depth of g~25.7mag (5{sigma}). Part of the survey was not covered or has shallow observations in the r band. We build two cluster catalogs: one using all bandpasses, for the fields with deep r-band observations (~20deg^2^), and the other using four bandpasses (u^*^,g,i,z) for the entire NGVS area. Based on our previous Canada-France-Hawaii Telescope Legacy Survey W1 studies, we estimate that both of our catalogs are ~100% (~70%) complete and ~80% pure, at z<=0.6 (z<~1), for galaxy clusters with masses of M>~10^14^M_{sun}_. We show that when using four bandpasses, though the photometric redshift accuracy is lower, RedGOLD detects massive galaxy clusters up to z~1 with completeness and purity similar to the five-band case. This is achieved when taking into account the bias in the richness estimation, which is ~40% lower at 0.5<=z<0.6 and ~20% higher at 0.6<z<0.8, with respect to the five-band case. RedGOLD recovers all the X-ray clusters in the area with mass M_500_>1.4x10^14^M_{sun}_ and 0.08<z<0.5. Because of our different cluster richness limits and the NGVS depth, our catalogs reach lower masses than the published redMaPPer cluster catalog over the area, and we recover ~90%-100% of its detections.
- ID:
- ivo://CDS.VizieR/J/ApJ/546/694
- Title:
- NICMOS star formation history
- Short Name:
- J/ApJ/546/694
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an extensive analysis of the star formation rates determined from the NICMOS deep images of the northern Hubble Deep Field. We use SED template fitting photometric techniques to determine both the redshift and the extinction for each galaxy in our field. Measurement of the individual extinctions provides a correction for star formation hidden by dust obscuration. We determine star formation rates for each galaxy based on the 1500{AA} UV flux and add the rates in redshift bins of width 1.0 centered on integer redshift values.
- ID:
- ivo://CDS.VizieR/J/ApJ/610/128
- Title:
- NIR colors of hard X-ray-selected AGN
- Short Name:
- J/ApJ/610/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of near-infrared photometry (J, H, K_s_) for a hard X-ray-selected sample of active galactic nuclei (AGNs) obtained from optical identification of the sources detected in ASCA surveys (total ~75deg^2^) with a flux limit of (1-3)x10^-13^erg/s/cm^2^ (2-10keV). The sample covers the AGNs at 0.1<~z<~1 with L_2-10keV_=10^42^-10^46^erg/s with very high completeness. The near-infrared photometric data of the sample are obtained from the Two Micron All Sky Survey (2MASS, Cat. <II/246>) and observations with Kitt Peak National Observatory 2.1m telescope and the University of Hawaii 2.2m telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/22
- Title:
- NIR galaxy cluster candidates in the SPT survey
- Short Name:
- J/ApJ/761/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the ground- and space-based optical and near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with the Sunyaev-Zel'dovich (SZ) effect in the 720deg^2^ of the South Pole Telescope (SPT) survey completed in the 2008 and 2009 observing seasons. We use the optical/NIR data to establish whether each candidate is associated with an overdensity of galaxies and to estimate the cluster redshift. Most photometric redshifts are derived through a combination of three different cluster redshift estimators using red-sequence galaxies, resulting in an accuracy of {Delta}z/(1+z)=0.017, determined through comparison with a subsample of 57 clusters for which we have spectroscopic redshifts. We successfully measure redshifts for 158 systems and present redshift lower limits for the remaining candidates. The redshift distribution of the confirmed clusters extends to z=1.35 with a median of z_med_=0.57. Approximately 18% of the sample with measured redshifts lies at z>0.8. We estimate a lower limit to the purity of this SPT SZ-selected sample by assuming that all unconfirmed clusters are noise fluctuations in the SPT data. We show that the cumulative purity at detection significance {xi}>5 ({xi}>4.5) is >=95% (>=70%). We present the red brightest cluster galaxy (rBCG) positions for the sample and examine the offsets between the SPT candidate position and the rBCG. The radial distribution of offsets is similar to that seen in X-ray-selected cluster samples, providing no evidence that SZ-selected cluster samples include a different fraction of recent mergers from X-ray-selected cluster samples.
- ID:
- ivo://CDS.VizieR/J/ApJS/239/22
- Title:
- NIR obs. of X-ray AGNs in COSMOS, SXDS & E-CDF-S
- Short Name:
- J/ApJS/239/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-IR spectroscopy in the J- and H-bands for a large sample of 243 X-ray-selected, moderate-luminosity Type 1 active galactic nuclei (AGNs) in the COSMOS, SXDS, and E-CDF-S survey fields using the multi-object spectrograph Subaru/FMOS. Our sample covers the redshift range 0.5<=z<=3.0 and X-ray luminosity range of 10^43^<=L_[2-10keV]_<=10^45^erg/s. We provide emission-line properties and derived virial black hole mass estimates, bolometric luminosities, and Eddington ratios, based on H{alpha} (211), H{beta} (63), and MgII (4). We compare line widths, luminosities, and black hole mass estimates from H{alpha} and H{beta}, and augment these with commensurate measurements of MgII and CIV detected in optical spectra. We demonstrate the robustness of using H{alpha}, H{beta}, and MgII as reliable black hole mass estimators for high-z moderate-luminosity AGNs, while the use of CIV is prone to large uncertainties (>=0.4dex). We extend a recently proposed correction based on the CIV blueshift to lower luminosities and black hole masses. While our sample shows an improvement in their CIV black hole mass estimates, the deficit of high blueshift sources reduces its overall importance for moderate-luminosity AGNs compared to the most luminous quasars. In addition, we revisit luminosity correlations between Lbol, L_[2-10keV]_, L[OIII], L5100, and LH{alpha} and find them to be consistent with a simple empirical model, based on a small number of well-established scaling relations. Finally, we highlight our highest redshift AGN, CID 781, at z=4.6, which has the lowest black hole mass (~10^8^M_{sun}_) among current near-IR samples at this redshift and is in a state of fast growth.
- ID:
- ivo://CDS.VizieR/J/ApJ/796/7
- Title:
- NIR spectral analysis of star-forming galaxies
- Short Name:
- J/ApJ/796/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M_*_/M_{sun}_)>=10.9) z~1-3 star-forming galaxies (SFGs) by increasing the sample size by a factor of six (to 44 galaxies above log(M_*_/M_{sun}_)>=10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS^3D^ spectroscopic surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/66
- Title:
- NIR spectra of 5 red quasars at 0.5<z<0.9
- Short Name:
- J/ApJ/812/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red quasars are thought to be an intermediate population between merger-driven star-forming galaxies in dust-enshrouded phase and normal quasars. If so, they are expected to have high accretion ratios, but their intrinsic dust extinction hampers reliable determination of Eddington ratios. Here, we compare the accretion rates of 16 red quasars at z~0.7 to those of normal type 1 quasars at the same redshift range. The red quasars are selected by their red colors in optical through near-infrared (NIR) and radio detection. The accretion rates of the red quasars are derived from the P{beta} line in NIR spectra, which is obtained by the SpeX on the Infrared Telescope Facility in order to avoid the effects of dust extinction. We find that the measured Eddington ratios (L_bol_/L_Edd_~=0.69) of red quasars are significantly higher than those of normal type 1 quasars, which is consistent with a scenario in which red quasars are the intermediate population and the black holes of red quasars grow very rapidly during such a stage.
- ID:
- ivo://CDS.VizieR/J/ApJ/806/L35
- Title:
- NIR spectroscopy of COSMOS FIR galaxies
- Short Name:
- J/ApJ/806/L35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123 far-infrared-selected galaxies in COSMOS and the key rest-frame optical emission lines. This is the largest sample of infrared galaxies with near-infrared spectroscopy at these redshifts. The far-infrared selection results in a sample of galaxies that are massive systems that span a range of metallicities in comparison with previous optically selected surveys, and thus has a higher active galactic nucleus (AGN) fraction and better samples the AGN branch. We establish the presence of AGNs and starbursts in this sample of (U)LIRGs selected as Herschel-PACS and Spitzer-MIPS detections in two redshift bins (z~0.7 and z~1.5) and test the redshift dependence of diagnostics used to separate AGNs from star formation dominated galaxies. In addition, we construct a low-redshift (z~0.1) comparison sample of infrared-selected galaxies and find that the evolution from z~1.5 to today is consistent with an evolving AGN selection line and a range of ISM conditions and metallicities from the models of Kewley et al. (2013ApJ...774L..10K). We find that a large fraction of (U)LIRGs are BPT-selected AGNs using their new redshift-dependent classification line. We compare the position of known X-ray-detected AGNs (67 in total) with the BPT selection and find that the new classification line accurately selects most of these objects (>70%). Furthermore, we identify 35 new (likely obscured) AGNs not selected as such by their X-ray emission. Our results have direct implications for AGN selection at higher redshift with either current (MOSFIRE, KMOS) or future (PFS, MOONS) spectroscopic efforts with near-infrared spectral coverage.
