- ID:
- ivo://CDS.VizieR/J/ApJS/208/28
- Title:
- H{alpha} survey in the ONC
- Short Name:
- J/ApJS/208/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an H{alpha} emission line survey in a 1 deg^2^ area centered on the Orion Nebula Cluster, obtained with the Wide Field Grism Spectrograph 2 on the 2.2 m telescope of the University of Hawaii. We identified 587 stars with H{alpha} emission, 99 of which, located mainly in the outer regions of the observed area, have not appeared in previous H{alpha} surveys. We determined the equivalent width (EW) of the line and, based on this, classified 372 stars as classical T Tauri stars (CTTSs) and 187 as weak-line T Tauri stars (WTTSs). Simultaneous r', i' photometry indicates a limiting magnitude of r' ~ 20 mag, but the sample is incomplete at r' > 17 mag. The surface distribution of the H{alpha} emission stars reveals a clustered population and a dispersed population, the former consisting of younger and more massive young stars than the latter. Comparison of the derived EWs with those found in the literature indicates variability of the H{alpha} line. We found that the typical amplitudes of the variability are not greater than a factor of two to three in most cases. We identified a subgroup of low-EW stars with infrared signatures indicative of optically thick accretion disks. We studied the correlations between the EW and other properties of the stars. Based on literature data, we examined several properties of our CTTS and WTTS subsamples and found significant differences in mid-infrared color indices, average rotational periods, and spectral energy distribution characteristics of the subsamples.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/335/10
- Title:
- H{alpha} survey of Abell 1689
- Short Name:
- J/MNRAS/335/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an H{alpha} survey in the rich cluster A 1689 at z=0.18, using the LDSS++ spectrograph on the Anglo-Australian Telescope (AAT). We obtained spectra covering redshifted H{alpha} at z=0.16-0.22, for 522 galaxies brighter than I=22.5, covering a field of 8.7x8.7arcmin^2^ (~1.1x1.1h^-1^Mpc at z=0.18). We securely detect H{alpha} emission in 46 of these galaxies; accounting for selection effects arising from sampling and cluster membership, we determine that 24+/-4 per cent of cluster members brighter than M_R_=-16.5+5logh are detected with H{alpha} flux greater than 4h^-2^x10^38^erg/s. From a Hubble Space Telescope mosaic covering 7.5x10.0arcmin, we determine morphologies for 199 galaxies brighter than I=21, and find that ~20 per cent of the cluster members are of type Sa or later. More than 90 per cent of cluster spirals show H{alpha} emission, compared with less than 10 per cent of E and S0 galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/1337
- Title:
- H{alpha} survey of cluster galaxies
- Short Name:
- J/MNRAS/357/1337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extended our H{alpha} objective prism survey of eight low-redshift clusters (viz. Abell 262, 347, 400, 426, 569, 779, 1367 and 1656) to include a complete sample of early-type galaxies within 1.5 Abell radii of the cluster centres. Of the 379 galaxies surveyed, 3 per cent of E, E-S0 galaxies, 6 per cent of S0 galaxies, and 9 per cent of S0/a galaxies were detected in emission. From a comparison of cluster and supercluster field galaxies, we conclude that the frequency of emission-line galaxies (ELGs; W>=20{AA}) is similar for field and cluster early-type galaxies. A similar result has previously been obtained for galaxies of types Sa and later. Together, these results confirm the inference of Biviano et al. (1997A&A...321...84B) that the relative frequency of ELGs in clusters and the field can be entirely accounted for by the different mix of morphological types between the differing environments, and that, for galaxies of a given morphological type, the fraction of ELGs is independent of environment. Detected emission is classified as 'compact' or 'diffuse', identified as circumnuclear starburst or active galactic nucleus (AGN) emission and disc emission, respectively. By comparing spectroscopic data for cluster early-type ELGs with data for field galaxies from the Palomar spectroscopic survey of nearby galactic nuclei, we demonstrate that there is modest evidence for an enhancement of compact H II emission relative to AGN emission in the early-type cluster ELGs as compared to the field. For the cluster early-type galaxies, compact H II emission correlates strongly with a disturbed morphology. This suggests that, as for later-type cluster galaxies, this enhanced compact H II emission can readily be explained as an enhancement of circumnuclear starburst emission due to gravitational tidal interactions, most likely caused by subcluster merging and other on-going processes of cluster virialization.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/36
- Title:
- H{alpha} survey of nearby clusters of galaxies
- Short Name:
- J/ApJS/199/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a wide-field H{alpha} imaging survey of eight nearby (z=0.02-0.03) Abell clusters. We have measured H{alpha} fluxes and equivalent widths for 465 galaxies, of which 360 are new detections. The survey was designed to obtain complete emission-line-selected inventories of star-forming galaxies in the inner regions of these clusters, extending to star formation rates below 0.1M_{sun}_/yr. This paper describes the observations, data processing, and source identification procedures, and presents an H{alpha} and R-band catalog of detected cluster members and other candidates. Future papers in the series will use these data to study the completeness of spectroscopically based star formation surveys, and to quantify the effects of cluster environment on the present-day populations of star-forming galaxies. The data will also provide a valuable foundation for imaging surveys of redshifted H{alpha} emission in more distant clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A91
- Title:
- Halpha3 survey of Virgo and Coma galaxies
- Short Name:
- J/A+A/553/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the galaxy structural parameters from H{alpha}3, an H{alpha} narrow-band imaging follow-up survey of ~800 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster, and in the Coma Supercluster. Taking advantage of H{alpha}3 which provides the complete census of the recent star-forming, HI-rich galaxies in the local universe, we aim to investigate the structural parameters of both the young (<10Myr) and the old (>1Gyr) stellar populations. By comparing the sizes of these stellar components we investigated the spatial scale on which galaxies are growing at the present cosmological epoch and the role of the environment in quenching the star-formation activity. We computed the concentration, asymmetry, and clumpiness (CAS) structural parameters both for recently born and old stars. To quantify the sizes we computed half-light radii and a new parameter dubbed EW/r based on the half-light radius of the H{alpha} Equivalent Width map. To highlight the environmental perturbation, we adopt an updated calibration of the HI-deficiency parameter that we use to divide the sample in unperturbed and perturbed galaxies. The concentration index computed in the r band depends on the stellar mass and on the Hubble type, these variables being related since most massive galaxies are bulge dominated thus most concentrated. Going toward later spirals and irregulars both the concentration index and the mass decrease along with the bulge-to-disk ratio. Blue Compact dwarfs represent an exception since they have similar mass but they are more concentrated than dwarf irregulars. The asymmetry and the clumpiness increase along the spiral sequence up to Sc-Sd but they decrease going toward dwarfs whose light distribution is smooth and more symmetric. When measured on H{alpha} images, the CAS parameters do not exhibit obvious correlations with Hubble type. Irrespective of whether we used the ratio between effective radii or the EW/r parameter, we found that the concentration index is the main parameter that describes the current growth of isolated galaxies but, for a fixed concentration, the stellar mass plays a second order role. At the present epoch, massive galaxies are growing inside-out, conversely the dwarfs are growing on the scale of their already assembled mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/25
- Title:
- H{alpha} & UV emission scale heights for edge-on gal.
- Short Name:
- J/ApJ/862/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare vertical profiles of the extraplanar H{alpha} emission to those of the UV emission for 38 nearby edge-on late-type galaxies. It is found that detection of the "diffuse" extraplanar dust (eDust), traced by the vertically extended, scattered UV starlight, always coincides with the presence of the extraplanar H{alpha} emission. A strong correlation between the scale heights of the extraplanar H{alpha} and UV emissions is also found; the scale height at H{alpha} is found to be ~0.74 of the scale height at FUV. Our results may indicate the multiphase nature of the diffuse ionized gas and dust in the galactic halos. The existence of eDust in galaxies where the extraplanar H{alpha} emission is detected suggests that a larger portion of the extraplanar H{alpha} emission than that predicted in previous studies may be caused by H{alpha} photons that originate from HII regions in the galactic plane and are subsequently scattered by the eDust. This possibility raise an advantage in studying the extraplanar diffuse ionized gas. We also find that the scale heights of the extraplanar emissions normalized to the galaxy size correlate well with the star formation rate surface density of the galaxies. The properties of eDust in our galaxies is on a continuation line of that found through previous observations of the extraplanar polycyclic aromatic hydrocarbons emission in more active galaxies known to have galactic winds.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A16
- Title:
- H{alpha}3 V. Coma cluster
- Short Name:
- J/A+A/576/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Neutral hydrogen represents the major observable baryonic constituent of galaxies that fuels the formation of stars through transformation of molecular hydrogen. The emission of the hydrogen recombination line H{alpha} is the most direct tracer of the process that transforms gas (fuel) into stars. We continue to present H{alpha}3 (acronym for H{alpha}-{alpha}{alpha}), an extensive H{alpha}+[NII] narrow-band imaging campaign of galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA), using the instrumentation available at the San Pedro Martir (SPM) observatory (Mexico). In 48 nights since 2011 we were able to carry out the H{alpha} imaging observations of 724 galaxies in the region of the Coma supercluster 10h<RA<16h ; 24{deg}<Dec<28{deg} and 3900<cz<9000km/s. Of these, 603 are selected from the ALFALFA and constitute a 97% complete sample. They provide for the first time a complete census of the massive star formation properties of local gas-rich galaxies belonging to different environments (cluster vs. filaments), morphological types (spirals vs. dwarf Irr), over a wide range of stellar mass (~10^8^-10^11.5^M_{sun}_) in the Coma supercluster. The present Paper V provides H{alpha} data and derived star formation rates for the observed galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/778/56
- Title:
- Hamburg/ESO Survey extremely metal-poor stars
- Short Name:
- J/ApJ/778/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From detailed abundance analysis of >100 Hamburg/ESO candidate extremely metal-poor (EMP) stars we find 45 with [Fe/H]<-3.0dex. We identify a heretofore unidentified group: Ca-deficient stars with sub-solar [Ca/Fe] ratios and the lowest neutron-capture abundances; the Ca-deficient group comprises ~10% of the sample, excluding Carbon stars. Our radial velocity distribution shows that the carbon-enhanced stars with no s-process enhancements, CEMP-no, and which do not show C_2_ bands are not preferentially binary systems. Ignoring Carbon stars, approximately 15% of our sample are strong (>=5{sigma}) outliers in one or more elements between Mg and Ni; this rises to ~19% if very strong (>=10{sigma}) outliers for Sr and Ba are included. Examples include: HE0305-0554 with the lowest [Ba/H] known; HE1012-1540 and HE2323-0256, two (non-velocity variable) C-rich stars with very strong [Mg,Al/Fe] enhancements; and HE1226-1149, an extremely r-process rich star.
- 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://nasa.heasarc/hrassoptid
- Title:
- Hamburg/RASS Catalog: Optical Identifications
- Short Name:
- HRASS/Opt
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table is a representation of part of the Hamburg/ROSAT All-Sky Survey (RASS) Catalog (HRC) of optical identifications of X-ray sources at high-galactic latitude, namely the list of proposed and possible optical identifications. (The list of the X-ray sources themselves is given in the linked Browse table HRASSCAT). The HRC includes all X-ray sources from the ROSAT Bright Source Catalog (RASS-BSC) with galactic latitude |b| >= 30 degrees and declination Dec >= 0 degrees. In this part of the sky covering ~10,000 square degrees, the RASS-BSC contains 5341 X-ray sources. For the optical identification, the HRC authors used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC, an identification could be given. For the rest, either no counterpart was visible in the error circle, or a plausible identification was not possible. With ~42%, AGN represent the largest group of X-ray emitters, ~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources, no object was visible on the blue direct plates within 40" around the X-ray source position. The catalog has been used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters. This table was produced by the HEASARC in February 2005 based on the CDS Catalog table J/A+A/406/353/optical.dat. This is a service provided by NASA HEASARC .