- ID:
- ivo://CDS.VizieR/J/AJ/151/120
- Title:
- z<1 3CR radio galaxies and quasars star formation
- Short Name:
- J/AJ/151/120
- Date:
- 16 Dec 2021 13:37:06
- Publisher:
- CDS
- Description:
- Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z<1. The far-infrared (FIR, 70-500 {mu}m) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer and cataloged data to analyze the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galactic nuclei (AGNs), and cool dust heated by stars. The level of emission from relativistic jets is also estimated to isolate the thermal host galaxy contribution. The new data are in line with the orientation-based unification of high-excitation radio-loud AGN, in that the dust torus becomes optically thin longwards of 30 {mu}m. The low-excitation radio galaxies and the MIR-weak sources represent an MIR- and FIR-faint AGN population that is different from the high-excitation MIR-bright objects; it remains an open question whether they are at a later evolutionary state or an intrinsically different population. The derived luminosities for host starlight and dust heated by star formation are converted to stellar masses and star-formation rates (SFR). The host-normalized SFR of the bulk of the 3CR sources is low when compared to other galaxy populations at the same epoch. Estimates of the dust mass yield a 1-100 times lower dust/stellar mass ratio than for the Milky Way, which indicates that these 3CR hosts have very low levels of interstellar matter and explains the low level of star formation. Less than 10% of the 3CR sources show levels of star formation above those of the main sequence of star-forming galaxies.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/897/44
- Title:
- 120 3<=z<=5 galaxies candidates in CANDELS fields
- Short Name:
- J/ApJ/897/44
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- Using the CANDELS photometric catalogs for the Hubble Space Telescope ACS and WFC3, we identified massive evolved galaxies at 3<z<4.5 employing three different selection methods. We find the comoving number density of these objects to be ~2x10^-5^ and 8x10^-6^/Mpc^3^ after correction for completeness for two redshift bins centered at z=3.4, 4.7. We quantify a measure of how much confidence we should have for each candidate galaxy from different selections and what the conservative error estimates propagated into our selection are. Then we compare the evolution of the corresponding number densities and their stellar mass density with numerical simulations, semianalytical models, and previous observational estimates, which shows slight tension at higher redshifts as the models tend to underestimate the number and mass densities. By estimating the average halo masses of the candidates (M_h_~4.2, 1.9, and 1.3x1012M{sun} for redshift bins centered at z=3.4, 4.1, and 4.7), we find them to be consistent with halos that were efficient in turning baryons to stars, relatively immune to the feedback effects, and on the verge of transition into hot-mode accretion. This can suggest the relative cosmological starvation of the cold gas followed by an overconsumption phase in which the galaxy rapidly consumes the available cold gas as one of the possible drivers for the quenching of the massive evolved population at high redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/684/905
- Title:
- z>1 galaxy clusters from IRAC Shallow Survey
- Short Name:
- J/ApJ/684/905
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 335 galaxy cluster and group candidates, 106 of which are at z>1, using a 4.5um-selected sample of objects from a 7.25deg^2^ region in the Spitzer Infrared Array Camera (IRAC) Shallow Survey. Clusters were identified as three-dimensional overdensities using a wavelet algorithm, based on photometric redshift probability distributions derived from IRAC and NOAO Deep Wide-Field Survey data. We estimate only ~10% of the detections are spurious. To date 12 of the z>1 candidates have been confirmed spectroscopically, at redshifts from 1.06 to 1.41. Velocity dispersions of ~750km/s for two of these argue for total cluster masses well above 10^14^M_{sun}_, as does the mass estimated from the rest-frame near-infrared stellar luminosity. Although not selected to contain a red sequence, some evidence for red sequences is present in the spectroscopically confirmed clusters, and brighter galaxies are systematically redder than the mean galaxy color in clusters at all redshifts.
- ID:
- ivo://CDS.VizieR/J/PASJ/65/113
- Title:
- 0.006<=z<=0.8 IR galaxies with AKARI
- Short Name:
- J/PASJ/65/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the 9 and 18um luminosity functions (LFs) of galaxies at 0.006<=z<=0.8 (with an average redshift of ~0.04) using the AKARI mid-infrared all-sky survey catalog. We selected 243 galaxies at 9um and 255 galaxies at 18um from the Sloan Digital Sky Survey (SDSS) spectroscopy region. These galaxies were then classified by their optical emission lines, such as the line width of H{alpha} or by their emission line ratios of [OIII]/H{beta} and [NII]/H{alpha} into five types: Type 1 active galactic nuclei (AGN) (Type 1); Type 2 AGN (Type 2); low-ionization narrow emission line galaxies (LINER); galaxies with both star formation and narrow-line AGN activity (composite galaxies); and star-forming galaxies (SF). We found that (i) the number density ratio of Type 2 to Type 1 AGNs is 1.73+/-0.36, which is larger than a result obtained from the optical LF and (ii) this ratio decreases with increasing 18um luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A73
- Title:
- ZJ VISTA photometry in NGC253 stellar halo
- Short Name:
- J/A+A/562/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use images obtained with the VISTA telescope in the Z and J bands to analyze the stellar content of NGC 253, a nearly edge on spiral galaxy in the Sculptor group. The very deep photometry, down to J~23.5, and the wide area covered allow us to trace the red giant branch and asymptotic giant branch (AGB) stars that belong to the outer disk and the halo of NGC 253, out to 50kpc along the galaxy minor axis. We confirm the existence of an extraplanar component, with a prominent southern shelf and detect for the first time a symmetrical feature on the north side. The star counts profile along the major axis show a clear break at 25kpc from the center, signalling the transition from the disk to the halo. The isodensity contours show a flat inner halo that blends with a more extended, diffuse, rounder outer halo. In such external structure, we detect an overdensity at about 28kpc from the plane and extending over 20kpc parallel with the disk of the galaxy. The spatially resolved color magnitude diagrams show a rather homogeneous stellar population across the tile. Particularly surprising is the presence of bright, intermediate age, AGB stars found scattered over a large volume.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/158
- Title:
- z<0.5 PG quasars IR energy distributions
- Short Name:
- J/ApJ/854/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are limited by sensitivity and other uncertainties. Dust provides an efficient indirect probe of the total gas. We apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. We present a comprehensive study of the full (1 to 500{mu}m) infrared spectral energy distributions of 87 redshift <0.5 quasars selected from the Palomar-Green sample, using photometric measurements from 2MASS, WISE, and Herschel, combined with Spitzer mid-infrared (5-40{mu}m) spectra. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. Most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive early-type galaxies. This result indicates that "quasar mode" feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. We also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. This cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/114
- Title:
- z~3-6 protoclusters in the CFHTLS deep fields
- Short Name:
- J/ApJ/826/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of three protoclusters at z~3-4 with spectroscopic confirmation in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields. In these fields, we investigate the large-scale projected sky distribution of z~3-6 Lyman-break galaxies and identify 21 protocluster candidates from regions that are overdense at more than 4{sigma} overdensity significance. Based on cosmological simulations, it is expected that more than 76% of these candidates will evolve into a galaxy cluster of at least a halo mass of 10^14^ M_{sun}_ at z=0. We perform follow-up spectroscopy for eight of the candidates using Subaru/FOCAS, Keck II/DEIMOS, and Gemini-N/GMOS. In total we target 462 dropout candidates and obtain 138 spectroscopic redshifts. We confirm three real protoclusters at z=3-4 with more than five members spectroscopically identified and find one to be an incidental overdense region by mere chance alignment. The other four candidate regions at z~5-6 require more spectroscopic follow-up in order to be conclusive. A z=3.67 protocluster, which has 11 spectroscopically confirmed members, shows a remarkable core-like structure composed of a central small region (<0.5 physical Mpc) and an outskirts region (~1.0 physical Mpc). The Ly{alpha} equivalent widths of members of the protocluster are significantly smaller than those of field galaxies at the same redshift, while there is no difference in the UV luminosity distributions. These results imply that some environmental effects start operating as early as at z~4 along with the growth of the protocluster structure. This study provides an important benchmark for our analysis of protoclusters in the upcoming Subaru/HSC imaging survey and its spectroscopic follow-up with the Subaru/PFS that will detect thousands of protoclusters up to z~6.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/105
- Title:
- z~5 QSO luminosity function from SDSS Stripe 82
- Short Name:
- J/ApJ/768/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a measurement of the Type I quasar luminosity function at z=5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M_1450_<-26) with Sloan Digital Sky Survey (SDSS) data covering ~6000deg^2^, then extend to lower luminosities (M_1450_<-24) with newly discovered, faint z~5 quasars selected from 235deg^2^ of deep, coadded imaging in the SDSS Stripe 82 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7<z<5.1 quasars that is highly complete, with 73 spectroscopic identifications out of 92 candidates. Our color selection method is also highly efficient: of the 73 spectra obtained, 71 are high-redshift quasars. These observations reach below the break in the luminosity function (M_1450_^*^~-27). The bright-end slope is steep ({beta}<~-4), with a constraint of {beta}<-3.1 at 95% confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of ~2 greater decrease in the number density of luminous quasars (M_1450_<-26) from z=5 to z=6 than from z=4 to z=5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate ~30% of the ionizing photons required to keep hydrogen in the universe ionized at z=5.
- 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.
- 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.
