- ID:
- ivo://CDS.VizieR/J/ApJ/792/L4
- Title:
- GV galaxies UV-optical radial color profiles
- Short Name:
- J/ApJ/792/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, with the Galaxy Evolution Explorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how the residual recent star formation is distributed in these galaxies. We find that the dust-corrected u-r colors of early-type galaxies (ETGs) are flat out to R_90_, while the colors monotonously turn blue when r>0.5 R_50_ for late-type galaxies (LTGs). More than half of the ETGs are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their star formations are centrally concentrated. The rest have flat color distributions out to R_90_. The centrally concentrated star formation activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ~50% of the ETGs have EW(H{alpha})>6.0 {AA}. Of the LTGs, 95% show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cores" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general model by which quenching first occurs in the core regions, and then finally extend to the rest of the galaxy. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/877/103
- Title:
- Half-mass radii for ~7000 galaxies at 1.0<=z<=2.5
- Short Name:
- J/ApJ/877/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial mass-to-light ratio gradients cause the half-mass and half-light radii of galaxies to differ, potentially biasing studies that use half-light radii. Here we present the largest catalog to date of galaxy half-mass radii at z>1: 7006 galaxies in the CANDELS fields at 1.0<=z<=2.5. The sample includes both star-forming and quiescent galaxies with stellar masses 9.0<=log(M_*_/M_{sun}_)<=11.5. We test three methods for calculating half-mass radii from multiband PSF-matched Hubble Space Telescope (HST) imaging: two based on spatially resolved spectral energy distribution modeling, and one that uses a rest-frame color profile. All three methods agree, with scatter <~0.3dex. In agreement with previous studies, most galaxies in our sample have negative color gradients (the centers are redder than the outskirts, and r_e,mass_<r_e,light_). We find that color gradient strength has significant trends with increasing stellar mass, half-light radius, U-V color, and stellar mass surface density. These trends have not been seen before at z>1. Furthermore, color gradients of star-forming and quiescent galaxies show a similar redshift evolution: they are flat at z>~2, then steeply decrease as redshift decreases. This affects the galaxy mass-size relation. The normalizations of the star-forming and quiescent r_mass_-M_*_ relations are 10%-40% smaller than the corresponding r_light_-M_*_ relations; the slopes are ~0.1-0.3dex shallower. Finally, the half-mass radii of star-forming and quiescent galaxies at M_*_=10^10.5^M_{sun}_ only grow by ~1% and ~8% between z~2.25 and z~1.25. This is significantly less than the ~37% and ~47% size increases found when using the half-light radius.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/1977
- Title:
- H-alpha emitters in/towards USS 1558
- Short Name:
- J/MNRAS/473/1977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out deep H{alpha} narrowband imaging with 10h net integrations towards the young protocluster, USS1558-003 at z=2.53 with the Subaru Telescope. This system is composed of four dense groups with massive local overdensities, traced by 107 H{alpha} emitters (HAEs) with stellar masses and dust-corrected star formation rates down to 1x10^8^M_{sun}_ and 3M_{sun}_/yr, respectively. We have investigated the environmental dependence of various physical properties within the protocluster by comparing distributions of HAEs in higher and lower densities with a standard Kolmogorov-Smirnov test. At 97 per cent confidence level, we find enhanced star formation across the star-forming main sequence of HAEs living in the most extreme 'supergroup', corresponding to the top quartile of overdensities. Furthermore, we derive distribution functions of H{alpha} luminosity and stellar mass in group and intergroup regions, approximately corresponding to 30 and 8 times higher densities than the general field. As a consequence, we identify 0.7 and 0.9dex higher cut-offs in H{alpha} luminosity and stellar mass functions in the dense groups, respectively. On the other hand, HAEs in the intergroup environment of the protocluster show similar distribution functions to those of field galaxies despite residing in significant overdensities. In the early phase of cluster formation, as inferred from our results, the densest parts in the protocluster have had an accelerated formation of massive galaxies. We expect that these eventually grow and transform into early-type galaxies at the bright end of the red sequence as seen in present-day rich clusters of galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/604/141
- Title:
- H{alpha} fluxes in Cl J0023+0423B galaxies
- Short Name:
- J/ApJ/604/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present H{alpha}-derived star formation rates (SFRs) for the galaxy cluster Cl J0023+0423B at z=0.845. Our 3{sigma} flux limits correspond to an SFR of 0.24h_100_^-2^M_{sun}_/yr, and our minimum reliable H{alpha}+[NII] equivalent width is greater than 10{AA}, demonstrating that near-infrared narrow-band imaging can sample the star-forming galaxy population in distant clusters. Comparison with spectroscopy shows that the number of false detections is low (9%+/-6%) and that our H{alpha} equivalent widths are correlated with spectroscopically determined [O II] equivalent widths. A magnitude-limited spectroscopic survey conducted over the same area missed 70% of the star-forming galaxies and 65% of the integrated star formation. Using Hubble Space Telescope Wide Field Planetary Camera 2 Archive images, we fit Sersic profiles to all galaxies with significant narrow-band equivalent widths and find that equivalent width decreases as the steepness of galaxy profile increases.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/16
- Title:
- H{alpha} & H{beta} spectral regions of low-z QSOs
- Short Name:
- J/ApJS/234/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the quasars with z_em_<0.9 from the Baryon Oscillation Spectroscopic Survey, we measure the spectral characteristics, including continuum and emission lines, around the H{beta} and H{alpha} spectral regions, which are lacking in Quasar Data Release 12 (DR12Q). We estimate the virial black hole mass from broad H{alpha} and/or H{beta}, and infer quasar redshifts from [OIII]{lambda}5007 emission lines. All the measurements and derived quantities are publicly available. A comparison between [OIII]{lambda}5007 redshifts and the visual inspection redshifts included in DR12Q indicates that the visual inspection redshifts are robust. We find that the full widths at half maximum of the broad H{alpha} are consistent with those of the broad H{beta}, while both the equivalent widths and line luminosities of the broad H{alpha} are obviously larger than the corresponding quantities of the broad H{beta}. We also find that there is an obviously systematic offset between the H{beta} and H{alpha} based mass if they are inferred from the empirical relationships in the literature. Using our large quasar sample, we have improved the H{beta} and H{alpha} based mass estimators by minimizing the difference between the H{beta}- and H{alpha}-based masses. For the black hole mass estimator (Equation (1)), we find that the coefficients (a,b)=(7.00,0.50) for H{alpha} and (a,b)=(6.96,0.50) for H{beta} are the best choices.
- ID:
- ivo://CDS.VizieR/J/ApJS/242/11
- Title:
- H{alpha} imaging survey of the 40% ALFALFA HI LSBGs
- Short Name:
- J/ApJS/242/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a narrow H{alpha}-band imaging survey of 357 low surface brightness galaxies (LSBGs) that are selected from the spring sky region of the 40% Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) HI Survey. All the H{alpha} images are obtained from the 2.16m telescope, operated by the Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences. We provide the H{alpha} fluxes and derive the global star formation rates (SFRs) of LSBGs after the Galactic extinction, internal extinction, and [NII] contamination correction. Compared to normal star-forming galaxies, LSBGs have a similar distribution in the HI surface density ({Sigma}HI), but their SFRs and star formation surface density ({Sigma}SFR) are much lower. Our results show that the gas-rich LSBGs selected from the ALFALFA survey obviously deviate from the Kennicutt-Schmidt law, in the relation between the star formation surface density ({Sigma}SFR) and the gas surface density ({Sigma}gas). However, they follow the extended Schmidt law well when taking the stellar mass of the galaxy into consideration.
- ID:
- ivo://CDS.VizieR/J/A+A/358/77
- Title:
- Hamburg/ESO survey for bright QSOs. III.
- Short Name:
- J/A+A/358/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Appendix to the above paper, containing the two large tables A.1 and B.1 described in the paper. Table A.1 gives the basic properties of the 207 survey fields used to construct the flux-limited sample, including field-dependent magnitude limits and adopted extinction values. Table B.1 lists the 415 QSOs and Seyfert 1 galaxies that form the sample, with positions, redshift and magnitudes, plus a cross-identification with the 1995 version of the AGN catalogue by Veron-Cetty & Veron (see Cat. <VII/215>).
- ID:
- ivo://CDS.VizieR/J/A+A/442/109
- Title:
- Hamburg/SAO Survey for ELGs. VI.
- Short Name:
- J/A+A/442/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the sixth list with results of the Hamburg/SAO Survey for Emission-Line Galaxies. The final list resulted from follow-up spectroscopy conducted with the 4.5m MMT telescope in 1996, and with 2.2m CAHA and 6m SAO telescopes in 2000 to 2003. The data of this snap-shot spectroscopy survey confirmed 134 emission-line objects out of 182 observed candidates and allowed their quantitative spectral classification and redshift determination. We classify 73 emission-line objects as definite or probable blue compact or HII galaxies (BCG), 8 as QSOs, 4 as Seyfert 1 and 2 galaxies. 30 low-excitation objects were classified as definite or probable starburst nuclei (SBN), 3 as dwarf amorphous nuclei starburst galaxies (DANS) and 2 as LINERs. Due to the low signal-to-noise ratio we could not classify 14 ELGs (NON). For another 9 galaxies we did not detect any significant emission lines. For 98 emission-line galaxies, the redshifts and/or line intensities are determined for the first time. For the remaining 28 previously-known ELGs we give either improved data the line intensities or some independent measurements. The detection rate of ELGs is ~70%. This paper completes the classification of strong-lined ELGs found in the zone of the Hamburg/SAO survey. Together with previously known BCG/HII galaxies in this zone, this sample of ~500 objects is the largest to date in a well bound region.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/5
- Title:
- HAQ survey: red QSO candidates follow-up
- Short Name:
- J/ApJS/217/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the ones used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared (near-IR) color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are confirmed to be QSOs. We use a statistical algorithm to identify sightlines with plausible intervening absorption systems and identify nine such cases assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We find absorption systems toward 30 QSOs, 2 of which are consistent with the best-fit absorber redshift from the statistical modeling. Furthermore, we observe a broad range in SED properties of the QSOs as probed by the rest-frame 2{mu}m flux. We find QSOs with a strong excess as well as QSOs with a large deficit at rest-frame 2{mu}m relative to a QSO template. Potential solutions to these discrepancies are discussed. Overall, our study demonstrates the high efficiency of the optical/near-IR selection of red QSOs.
- ID:
- ivo://CDS.VizieR/J/A+A/466/823
- Title:
- Hard 2-10kev X-ray selected sources
- Short Name:
- J/A+A/466/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra and Spitzer data for the 186, extragalactic, hard 2-10keV X-ray selected sources, which lie in the central part of the Chandra Deep Field South (CDFS). For the vast majority of sources (99.5%), there is a spectroscopic or photometric redshift available. We classify 17 sources as X-ray obscured QSOs, strictly according to X-ray criteria, i.e. defined as having large hydrogen column densities (NH>10^22cm^-2^) and luminosities (LX>10^44^erg/s). The surface density of X-ray obscured QSOs is ~210{deg}^-2^. We find 18 candidate Compton-thick NH>10^24^cm^-2^ sources, of which three have QSO luminosities (LX>10^44^erg/s). The X-ray obscured QSO comprise a mixed bag of objects, covering the redshift range z=1.3-4.3. Eight of these show narrow-line optical spectra, two show no obscuration in their optical spectra that present broad lines, while for the other seven there is only a photometric redshift available. About half of the X-ray obscured QSOs show high X-ray to optical flux ratios, X/O>1, and red colours, I-3.6{mu}m>4. Combining the X-ray with the mid-IR 8{mu}m or 24{mu}m flux can be used as an additional diagnostic to sift out the heavily obscured AGN. All X-ray selected QSOs present red mid-IR colours and can be easily separated among mid-IR sources, demonstrating that mid-IR selection provides a powerful tool for detecting obscured QSOs.
