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611. H{alpha} & H{beta} spectral regions of low-z QSOs
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.
612. H{alpha} imaging of Herschel Reference Survey
ID:
ivo://CDS.VizieR/J/A+A/579/A102
Title:
H{alpha} imaging of Herschel Reference Survey
Short Name:
J/A+A/579/A102
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new H{alpha}+[NII] imaging data of late-type galaxies in the Herschel Reference Sample aimed at studying the star formation properties of a K-band-selected, volume-limited sample of nearby galaxies. The H{alpha}+[NII] data are corrected for [NII] contamination and dust attenuation using different recipes based on the Balmer decrement and the 24um luminosities. We show that the H{alpha} luminosities derived with different corrections give consistent results only whenever the the uncertainty on the estimate of the Balmer decrement is [C(H{beta})]<=0.1. We use these data to derive the star formation rate of the late-type galaxies of the sample, and compare these estimates to those determined using independent monochromatic tracers (FUV, radio continuum) or the output of spectral energy distribution (SED) fitting codes. This comparison suggests that the 24um based dust extinction correction for the H{alpha} data might be non universal, and that it should be used with caution in all objects with a low star formation activity, where dust heating can be dominated by the old stellar population. Furthermore, because of the sudden truncation of the star formation activity of cluster galaxies occurring after their interaction with the surrounding environment, the stationarity conditions required to transform monochromatic fluxes into star formation rates might not always be satisfied in tracers other than the H{alpha} luminosity. In a similar way, the parametrisation of the star formation history generally used in SED fitting codes might not be adequate for these recently interacting systems. We then use the derived star formation rates to study the SFR luminosity distribution and the typical scaling relations of the late-type galaxies of the HRS. We observe a systematic decrease of the specific star formation rate with increasing stellar mass, stellar mass surface density, and metallicity. We also observe an increase of the asymmetry and smoothness parameters measured in the H{alpha}-band with increasing SSFR, probably induced by an increase of the contribution of giant HII regions to the H{alpha} luminosity function in star-forming low-luminosity galaxies.
613. H{alpha} indices in M low-mass stars
ID:
ivo://CDS.VizieR/J/ApJ/764/3
Title:
H{alpha} indices in M low-mass stars
Short Name:
J/ApJ/764/3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using the High Resolution Spectrograph on the Hobby-Eberly Telescope. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H{alpha} feature. We have identified periodic signals for six stars, with periods ranging from days to more than 10 years, and find long-term trends for seven others. Stellar cycles with P>=1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H{alpha} variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H{alpha} variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f in that system. In general, though, we find that H{alpha} is not frequently correlated with RV at the precision (typically 6-7m/s) of our measurements.
614. H{alpha}+[NII] observations of M81 HII regions
ID:
ivo://CDS.VizieR/J/AJ/126/1286
Title:
H{alpha}+[NII] observations of M81 HII regions
Short Name:
J/AJ/126/1286
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a first of a series of studies of the H{alpha}+[NII] emission from nearby spiral galaxies, we present measurements of H{alpha}+[NII] emission from HII regions in M81. Our method uses large-field CCD images and long-slit spectra and is part of the ongoing Beijing-Arizona-Taipei-Connecticut Sky Survey (the BATC survey). The CCD images are taken with the National Astronomical Observatories of China (NAOC) 0.6/0.9m f/3 Schmidt telescope at the Xinglong Observing Station, using a multicolor filter set. The observations reported here were taken on 30 individual nights over the time period 1995 February 5 to 1997 February 19. Spectra of 10 of the brightest HII regions are obtained using the NAOC 2.16m telescope with a Tek 1024x1024 CCD, between 1997 April 9 and 11. The continua of the spectra are calibrated by flux-calibrated images taken from the Schmidt observations. We determine the continuum component of our H{alpha}+[NII] image via interpolation from the more accurately measured backgrounds (M81 starlight) obtained from the two neighboring (in wavelength) BATC filter images. We use the calibrated fluxes of H{alpha}+[NII] emission from the spectra to normalize this interpolated, continuum-subtracted H{alpha}+[NII] image. We estimate the zero-point uncertainty of the measured H{alpha}+[NII] emission flux to be 8%. A catalog of H{alpha}+[NII] fluxes for 456 HII regions is provided, with those fluxes being on a more consistent linear scale than previously available. The logarithmically binned H{alpha}+[NII] luminosity function of HII regions is found to have slope {alpha}=-0.70, consistent with previous results (which allowed {alpha}=-0.5 to -0.8). From the overall H{alpha}+[NII] luminosity of the HII regions, the star formation rate of M81 is found to be ~0.68M_{sun}_/yr, modulo uncertainty with extinction corrections.
615. H{alpha} observations of UV-selected galaxies
ID:
ivo://CDS.VizieR/J/ApJ/647/128
Title:
H{alpha} observations of UV-selected galaxies
Short Name:
J/ApJ/647/128
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using Halpha spectra of 114 rest-frame UV-selected galaxies at z~2, we compare inferred star formation rates (SFRs) with those determined from the UV continuum luminosity. After correcting for extinction using standard techniques based on the UV continuum slope, we find excellent agreement between the indicators, with <SFR_Ha_>=31M_{sun}_/yr and <SFR_UV_>=29M_{sun}_/yr. The agreement between the indicators suggests that the UV luminosity is attenuated by a typical factor of ~4.5 (ranging from no attenuation to a factor of 100 for the most obscured object in the sample), in good agreement with estimates of obscuration from X-ray, radio, and mid-IR data.
616. H{alpha} photometry of face-on galaxies
ID:
ivo://CDS.VizieR/J/ApJS/166/505
Title:
H{alpha} photometry of face-on galaxies
Short Name:
J/ApJS/166/505
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a survey of the photometric and kinematic properties of 39 nearby, nearly face-on disk galaxies. Our approach exploits echelle-resolution integral-field spectroscopy of the H{alpha} regions, obtained with DensePak on the WIYN 3.5m telescope Bench Spectrograph. These data are complemented by HI line profiles observed with the Nancay radio telescope for 25 of these sample galaxies. Twelve additional line widths are available for sample galaxies from the literature. In this paper, we introduce the goals of this survey, define the sample selection algorithm, and amass the integral field spectroscopic data and HI line widths. We establish spatially integrated H{alpha} line widths for the sample. We test the veracity of these spatially integrated line profiles by convolving narrowband imaging data with velocity field information for one of the sample galaxies, PGC 38268, and also by comparing to HI line profiles.
617. H{alpha} profiles of Be stars
ID:
ivo://CDS.VizieR/J/ApJS/187/228
Title:
H{alpha} profiles of Be stars
Short Name:
J/ApJS/187/228
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a set of theoretical H{alpha} emission-line profiles of Be stars, created by systematically varying model input parameters over a wide range of accepted values. Models were generated with a non-LTE radiative transfer code that incorporates a non-isothermal disk structure and a solar-type chemical composition. The theoretical H{alpha} emission-line profiles were compared to a large set of Be star spectra with the aim of reproducing their global characteristics. We find that the observed profile shapes cannot be used to uniquely determine the inclination angle of Be star+disk systems. Drastically different profile shapes arise at a given inclination angle as a direct result of the state of the gas, and self-consistent disk physical conditions are therefore crucial for interpreting the observations.
618. H{alpha} spectroscopy in IC 1396 HII region
ID:
ivo://CDS.VizieR/J/AJ/143/61
Title:
H{alpha} spectroscopy in IC 1396 HII region
Short Name:
J/AJ/143/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have made an extensive survey of emission-line stars in the IC 1396 H II region to investigate the low-mass population of pre-main-sequence (PMS) stars. A total of 639 H{alpha} emission-line stars were detected in an area of 4.2deg^2^ and their i' photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H II region (Rim B and SFO 37, 38, 39, 41), and near HD206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared color-color diagram, we have selected PMS star candidates associated with IC1396. The age and mass were derived from the extinction-corrected color-magnitude diagram and theoretical PMS tracks. Most of our PMS candidates have ages of <3Myr and masses of 0.2-0.6M_{sun}_. Although it appears that only a few stars were formed in the last 1Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered the formation of many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.
619. H{alpha} survey in the ONC
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.
620. H{alpha} survey of Abell 1689
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.