- ID:
- ivo://CDS.VizieR/J/MNRAS/447/1126
- Title:
- Halpha measurements in Abell 2465
- Short Name:
- J/MNRAS/447/1126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the star formation rate and its location in the major merger cluster Abell 2465 at z=0.245. Optical properties of the cluster are described in. Measurements of the H{alpha} and infrared dust emission of galaxies in the cluster were made with an interference filter centred on the redshifted line at a wavelength of 817 nm and utilized data from the Wide-field Infrared Survey Explorer satellite 12{mu}m band. Imaging in the Johnson U and B bands was obtained, and along with Sloan Digital Sky Survey u and r was used to study the blue fraction, which appears enhanced, as a further signature of star formation in the cluster. Star formation rates were calculated using standard calibrations. The total star formation rate normalized by the cluster mass, {Sigma}SFR/M_cl_ compared to compilations for other clusters indicate that the components of Abell 2465 lie above the mean z and M_cl_ relations, suggestive that interacting galaxy clusters have enhanced star formation. The projected radial distribution of the star-forming galaxies does not follow an NFW profile and is relatively flat indicating that fewer star-forming galaxies are in the cluster centre. The morphologies of the H{alpha} sources within R_200_ for the cluster as a whole indicate that many are disturbed or merging, suggesting that a combination of merging or harassment is working.
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- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/161/191
- Title:
- H{alpha} photometry in NGC 7020
- Short Name:
- J/AJ/161/191
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- The galaxy NGC7020 displays an exotic hexagonal ringlike central structure with conspicuous ansae located at two opposite vertices and a tenuous external ring populated by H ii regions. Inside and around the hexagonal structure, H{alpha} emission is also present at the inner disk. To characterize the population of the HII regions, as well as their ionizing clusters, we imaged NGC7020 with narrowband H{alpha} and nearby continuum filters attached to GMOS-S installed on the Gemini South telescope. We found 202 HII regions or complexes of HII regions evenly distributed between the outer ring and the central disk The nucleus and ansae also present H{alpha} emission. The equivalent width of the H{alpha} line (WH{alpha}) is systematically greater at the regions of the outer ring relative to those of the inner disk. We discuss the influence of the metallicity gradient of the disk and the upper limit of the masses of the initial mass function on WH{alpha}, and we conclude that the data are still consistent with the occurrence of a younger burst of HII region formation in the outer ring. The central regions present more massive clusters, M>~106M{sun}, than those of the outer ring (M<~106M{sun}). Three clusters within 5" of the nucleus present masses higher than 108M{sun}. The presence of diffuse H{alpha} emission in the inner 5" suggests gas flows in the nuclear region.
- ID:
- ivo://CDS.VizieR/II/24
- Title:
- H-{alpha} Photometry of Northern Late-Type Stars I.
- Short Name:
- II/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations are presented of the strength of the H-{alpha} absorption line in the spectra of approximately 600 northern F, G and K stars of differing luminosities and chemical compositions. Most of the stars in this catalogue were previously observed by Griffin and Redman (1960MNRAS.120..287G), Deeming (1960MNRAS.121...52D), and Griffin (1961MNRAS.122..181G). Data given in this catalog include HD number, MK spectral classification, high velocity, (B-V) color index, magnesium b ratio, sodium D line ratio and H-{alpha} ratio.
- ID:
- ivo://CDS.VizieR/II/22
- Title:
- H{alpha} photometry of Southern F-G dwarfs
- Short Name:
- II/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H{alpha} photometry is presented for 172 southern F, G, and K type stars, mostly of luminosity classes V and IV. The bands measured, using a spectroscopic resolution of 3.4{AA}/mm, were: H{alpha}: 6546.5-6582.5{AA} comparison regions: 6469.0-6505.0{AA} and 6624.0-6660.0{AA}.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/86
- Title:
- H{alpha} spectra & V-band photometry of {delta} Sco
- Short Name:
- J/ApJ/890/86
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- We model the circumstellar disk of {delta} Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models through matching simulated observations to actual H{alpha} spectroscopy and V-band photometric observations. Our modeling results confirm previous findings that the disk of {delta}Sco was forming early in the century. We also find a period of disk dissipation when the companion is at apastron, as well as a significant growth of the disk between 2009 and 2011, prior to the periastron of 2011. Due to the steady-state nature of the disk after 2011, it is difficult to say whether the variations seen are due to the effect of the close passage of the binary companion.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/4180
- Title:
- H{alpha} stars in M31 HST photometry
- Short Name:
- J/MNRAS/465/4180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 224 stars that emit H{alpha} (H{alpha} stars) in the Andromeda galaxy (M31). The stars were selected from ~5000 spectra, collected as part of the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey using Keck II/DEIMOS. We used six-filter Hubble Space Telescope photometry from the Panchromatic Hubble Andromeda Treasury survey to classify and investigate the properties of the H{alpha} stars. We identified five distinct categories of H{alpha} star: B-type main-sequence (MS) stars, 'transitioning'-MS (T-MS) stars, red core He burning (RHeB) stars, non-C-rich asymptotic giant branch (AGB) stars, and C-rich AGB stars. We found that ~12 per cent of B-type stars exhibit H{alpha} emission (Be stars). The frequency of Be to all B stars is known to vary with the metallicity of their environment. Comparing this proportion of Be stars with other environments around the Local Group, the result could indicate that M31 is more metal-rich than the Milky Way. We predict that the 17 T-MS H{alpha} stars are Be stars evolving off the MS with fading H{alpha} emission. We separated RHeB from AGB H{alpha} stars. We conclude that the 61 RHeB and AGB stars are likely to be long-period variables. We found that ~14 per cent of C-rich AGB stars (C stars) emit H{alpha}, which is an upper limit for the ratio of C-rich Miras to C stars. This catalogue of H{alpha} stars will be useful to constrain stellar evolutionary models, calibrate distance indicators for intermediate-age populations, and investigate the properties of M31.
- ID:
- ivo://CDS.VizieR/J/A+A/446/839
- Title:
- H{alpha} surface photometry in nearby clusters
- Short Name:
- J/A+A/446/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the H{alpha} imaging observations of 273 late-type galaxies in the nearby rich galaxy clusters Virgo, A 1367, Coma, Cancer, Hercules and in the Great Wall, carried out primarily with the 2.1m telescope of the San Pedro Martir Observatory (SPM) and with the ESO/3.6m telescope. We derived the H{alpha}+[NII] fluxes and equivalent widths. The H{alpha} survey reached completion for an optically selected sample of nearby galaxies in and outside rich clusters. Taking advantage of the completeness of the data set, the dependence of H{alpha} properties on the Hubble type was determined for late-type galaxies in the Virgo cluster. Differences in the gaseous content partly account for the large scatter of the H{alpha} EW within each Hubble-type class. We studied the radial distributions of the H{alpha} EW around Coma+A 1367 and the Virgo clusters in two luminosity bins. Luminous galaxies show a decrease in their average H{alpha} EW in the inner ~1 virial radius, while low-luminosity galaxies do not show this trend. Description:
- ID:
- ivo://CDS.VizieR/J/A+A/396/449
- Title:
- H{alpha} surface photometry in Virgo
- Short Name:
- J/A+A/396/449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H{alpha}+[NII] imaging observations of 369 late-type (spiral) galaxies in the Virgo cluster and in the Coma/A1367 supercluster are analyzed, covering 3 rich nearby clusters (A1367, Coma and Virgo) and nearly isolated galaxies in the Great-Wall. They constitute an optically selected sample (mp<16.0) observed with ~60% completeness. These observations provide us with the current (T<10^7^yrs) star formation properties of galaxies that we study as a function of the clustercentric projected distances (Theta). The expected decrease of the star formation rate (SFR), as traced by the H{alpha} equivalent width, with decreasing Theta is found only when galaxies brighter than Mp~19.5 are considered. Fainter objects show no or reverse trends. We also include in our analysis Near Infrared data, providing information on the old (T>10^9^yrs) stars. Put together, the young and the old stellar indicators give the ratio of currently formed stars over the stars formed in the past, or "birthrate" parameter b. For the considered galaxies we also determine the "global gas content" combining HI with CO observations. We define the "gas deficiency'' parameter as the logarithmic difference between the gas content of isolated galaxies of a given Hubble type and the measured gas content.
