- ID:
- ivo://CDS.VizieR/J/MNRAS/437/2607
- Title:
- Low X-ray luminosity galaxy clusters
- Short Name:
- J/MNRAS/437/2607
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second of a series of papers on low X-ray luminosity galaxy clusters, in which we present the r', g' and i' photometry obtained with Gemini Multi-Object Spectrograph IMAGE at Gemini North and South telescopes for seven systems in the redshift range of 0.18 to 0.70. Optical magnitudes, colours and morphological parameters, namely, concentration index, ellipticity and visual morphological classification, are also given. At lower redshifts, the presence of a well-defined red cluster sequence extending by more than 4mag showed that these intermediate-mass clusters had reached a relaxed stage. This was confirmed by the small fraction of blue galaxy members observed in the central regions of ~0.75Mpc. In contrast, galaxy clusters at higher redshifts had a less important red cluster sequence. We also found that the galaxy radial density profiles in these clusters were well fitted by a single power law. At 0.18<z<0.70, we observed an increasing fraction of blue galaxies and a decreasing fraction of lenticulars, with the early-type fraction remaining almost constant. Overall, the results of these intermediate-mass clusters are in agreement with those for high-mass clusters.
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Search Results
302. LRG catalog
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1608
- Title:
- LRG catalog
- Short Name:
- J/MNRAS/380/1608
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work I discuss the necessary steps for deriving photometric redshifts for luminous red galaxies (LRGs) and galaxy clusters through simple empirical methods. The data used are from the Sloan Digital Sky Survey (SDSS). I show that with three bands only (gri) it is possible to achieve results as accurate as the ones obtained by other techniques, generally based on more filters. In particular, the use of the (g-i) colour helps improving the final redshifts (especially for clusters), as this colour monotonically increases up to z~0.8. For the LRGs I generate a catalogue of ~1.5 million objects at z<0.70. The accuracy of this catalogue is sigma=0.027 for z<=0.55 and sigma=0.049 for 0.55<z<=0.70. The photometric redshift technique employed for clusters is independent of a cluster selection algorithm. Thus, it can be applied to systems selected by any method or wavelength, as long as the proper optical photometry is available. When comparing the redshift listed in literature to the photometric estimate, the accuracy achieved for clusters is sigma=0.024 for z<=0.30 and sigma=0.037 for 0.30<z<=0.55. However, when considering the spectroscopic redshift as the mean value of SDSS galaxies on each cluster region, the accuracy is at the same level as found by other authors: sigma=0.011 for z<=0.30 and sigma=0.016 for 0.30<z<=0.55. The photometric redshift relation derived here is applied to thousands of cluster candidates selected elsewhere. I have also used galaxy photometric redshifts available in SDSS to identify groups in redshift space and then compare the redshift peak of the nearest group to each cluster redshift. This procedure provides an alternative approach for cluster selection, especially at high redshifts, as the cluster red sequence may be poorly defined.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/1605
- Title:
- Luminous K-band selected QSOs from UKIDSS
- Short Name:
- J/MNRAS/386/1605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The largest K-band flux-limited sample of luminous quasars to date has been constructed from the UKIRT (UK Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey Early Data Release, covering an effective area of 12.8deg^2^. Exploiting the K-band excess (KX) of all quasars with respect to foreground stars, including quasars experiencing dust reddening and objects with non-standard spectral energy distributions (SEDs), a list of targets suitable for spectroscopic follow-up observations with the AAOmega multi-object spectrograph is constructed, resulting in more than 200 confirmed active galactic nuclei (AGN). KX selection successfully identifies as quasar candidates objects that are excluded from the Sloan Digital Sky Survey (SDSS) quasar selection algorithm due to their colours being consistent with the stellar locus in optical colour space (with the space density of the excluded objects agreeing well with results from existing completeness analyses). Nearly half of the KX-selected quasars with K<=17.0 at z<3 are too faint in the i band to have been targeted by the SDSS quasar selection algorithm, revealing a large population of quasars with red i-K colours.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/33
- Title:
- Luminous of high-z QSOs with SDSS and WISE. II
- Short Name:
- J/ApJ/829/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper in a series on a new luminous z~5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z~5. Combining our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z~5 quasar sample to date, with 99 quasars in the range of 4.7<=z<5.4 and -29<M_1450_<=-26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/V_a_ method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as {alpha}=-2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope {beta}=-3.58+/-0.24 and a fainter break magnitude M_1450_^*^=-26.98+/-0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a luminosity evolution and density evolution model. Using the best-fit QLF, the contribution of quasars to the ionizing background at z~5 is found to be 18%-45% with a clumping factor C of 2-5. Our sample suggests an evolution of radio loud fraction with optical luminosity but no obvious evolution with redshift.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/117
- Title:
- Luminous (sub-)millimetre galaxies
- Short Name:
- J/MNRAS/444/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motivated by the current controversy over the redshift distribution and physical properties of luminous (sub-)mm sources, we have undertaken a new study of the brightest sample of unlensed (sub-)mm sources with pre-Atacama Large Millimeter/submillimeter Array (ALMA) interferometric follow-up in the Cosmological Evolution Survey field. Exploiting the very latest multifrequency supporting data, we find that this sample displays a redshift distribution indistinguishable from that of the lensed sources uncovered with the South Pole Telescope, with z_median_=~3.5. We also find that, over the redshift range z=~2-6, the median stellar mass of the most luminous (sub-) mm sources is M_*_=~ 3x10^11^M_{sun}_, yielding a typical specific star formation rate sSFR=~3Gyr^-1^. Consistent with recent ALMA and the Submillimeter Array studies, we confirm that source blending is not a serious issue in the study of luminous (sub-)mm sources uncovered by ground-based, single-dish surveys; only =~10^-15^% of bright (S_850_=~5-10mJy) (sub-) mm sources arise from significant (i.e. >20%) blends, and so our conclusions are largely unaffected by whether we adopt the original single-dish mm/sub-mm flux densities/positions or the interferometric data. Our results suggest that apparent disagreements over the redshift distribution of (sub-)mm sources are a result of 'down-sizing' in dust-enshrouded star formation, consistent with existing knowledge of the star formation histories of massive galaxies. They also indicate that extreme star-forming galaxies at high redshift are, on average, subject to the same star formation rate-limiting processes as less luminous objects, and lie on the 'main sequence' of star-forming galaxies at z>3.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/37
- Title:
- Luminous WISE-selected quasars in SDSS Stripe 82
- Short Name:
- J/ApJ/861/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopically complete sample of 147 infrared-color-selected active galactic nuclei (AGNs) down to a 22{mu}m flux limit of 20mJy over the ~270deg^2^ of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (Lbol>~10^12^L_{sun}_) and are found out to z~3. We classify the AGNs into three types, finding 57 blue, unobscured Type-1 (broad-lined) sources; 69 obscured, Type-2 (narrow-lined) sources; and 21 moderately reddened Type-1 sources (broad-lined and E(B-V)>0.25). We study a subset of this sample in X-rays and analyze their obscuration to find that our spectroscopic classifications are in broad agreement with low, moderate, and large amounts of absorption for Type-1, red Type-1, and Type-2 AGNs, respectively. We also investigate how their X-ray luminosities correlate with other known bolometric luminosity indicators such as [OIII] line luminosity (L[OIII]) and infrared luminosity (L6{mu}m). While the X-ray correlation with L[OIII] is consistent with previous findings, the most infrared-luminous sources appear to deviate from established relations such that they are either underluminous in X-rays or overluminous in the infrared. Finally, we examine the luminosity function evolution of our sample, and by AGN type, in combination with the complementary, infrared-selected, AGN sample of Lacy et al. (2013), spanning over two orders of magnitude in luminosity. We find that the two obscured populations evolve differently, with reddened Type-1 AGNs dominating the obscured AGN fraction (~30%) for L_5{mu}m_>10^45^erg/s, while the fraction of Type-2 AGNs with L_5{mu}m_<10^45^erg/s rises sharply from 40% to 80% of the overall AGN population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/881
- Title:
- LVL global optical photometry
- Short Name:
- J/MNRAS/445/881
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the global optical photometry of 246 galaxies in the Local Volume Legacy (LVL) survey. The full volume-limited sample consists of 258 nearby (D<11Mpc) galaxies whose absolute B-band magnitude span a range of -9.6<M_B_<-20.7mag. A composite optical (UBVR) data set is constructed from observed UBVR and Sloan Digital Sky Survey ugriz imaging, where the ugriz magnitudes are transformed into UBVR. We present photometry within three galaxy apertures defined at UV, optical, and IR wavelengths. Flux comparisons between these apertures reveal that the traditional optical R25 galaxy apertures do not fully encompass extended sources. Using the larger IR apertures, we find colour-colour relationships where later type spiral and irregular galaxies tend to be bluer than earlier type galaxies. These data provide the missing optical emission from which future LVL studies can construct the full panchromatic (UV-optical-IR) spectral energy distributions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/316
- Title:
- Lyman continuum LAEs and LBGs in SSA22 field
- Short Name:
- J/MNRAS/465/316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest to date sample of hydrogen Lyman continuum (LyC) emitting galaxy candidates at any redshift, with 18 Lyman {alpha} emitters (LAEs) and seven Lyman break galaxies (LBGs), obtained from the SSA22 field with Subaru/Suprime-Cam. The sample is based on the 159 LAEs and 136 LBGs observed in the field, all with spectroscopically confirmed redshifts, and these LyC candidates are selected as galaxies with counterparts in a narrow-band filter image which traces LyC at z>=3.06. Many LyC candidates show a spatial offset between the rest-frame non-ionizing ultraviolet (UV) detection and the LyC-emitting substructure or between the Ly{alpha} emission and LyC. The possibility of foreground contamination complicates the analysis of the nature of LyC emitters, although statistically it is highly unlikely that all candidates in our sample are contaminated by foreground sources. Many viable LyC LAE candidates have flux density ratios inconsistent with standard models, while also having too blue UV slopes to be foreground contaminants. Stacking reveals no significant LyC detection, suggesting that there is a dearth of objects with marginal LyC signal strength, perhaps due to a bimodality in the LyC emission. The foreground contamination corrected 3{sigma} upper limits of the observed average flux density ratios are fLyC/fUV < 0.08 from stacking LAEs and f_LyC_/f_UV_<0.02 from stacking LBGs. There is a sign of a positive correlation between LyC and Ly{alpha}, suggesting that both types of photons escape via a similar mechanism. The LyC detection rate among protocluster LBGs is seemingly lower compared to the field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/302
- Title:
- Lyman continuum leaking AGN in SSA22 field
- Short Name:
- J/MNRAS/465/302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin nature or are foreground contaminants. The remaining two LyC candidates are type I AGN. We argue that the average LyC escape fraction of high-redshift, low-luminosity AGN is not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of 2 lower than values obtained assuming f_esc_=1. Comparing to recent Ly{alpha} forest measurements, AGNs at redshift z~3 make up at most ~12 per cent and as little as ~5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/151
- Title:
- Lyman cont. luminosity of SDSS quasar pairs at z~3
- Short Name:
- J/ApJ/884/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used spectra of 181 projected quasar pairs at separations <=1.5' from the Sloan Digital Sky Survey Data Release 12 in the redshift range of 2.5-3.5 to probe the proximity regions of the foreground quasars. We study the proximity effect both in the longitudinal and in the transverse directions, by carrying out a comparison of the Ly{alpha} absorption lines originating from the vicinity of quasars to those originating from the general intergalactic medium at the same redshift. We found an enhancement in the transmitted flux within 4Mpc to the quasar in the longitudinal direction. However, the trend is found to be reversed in the transverse direction. In the longitudinal direction, we derived an excess overdensity profile showing an excess up to r<=5Mpc after correcting for the quasar's ionization, taking into account the effect of low spectral resolution. This excess overdensity profile matches with the average overdensity profile in the transverse direction without applying any correction for the effect of the quasar's ionization. Among various possible interpretations, we found that the anisotropic obscuration of the quasar's ionization seems to be the most probable explanation. This is also supported by the fact that all of our foreground quasars happen to be type 1 AGNs. Finally, we constrain the average quasar's illumination along the transverse direction as compared to that along the longitudinal direction to be <=27% (3{sigma} confidence level).
