- ID:
- ivo://CDS.VizieR/J/A+A/384/383
- Title:
- H{alpha} galaxies in Abell 1367 and Coma
- Short Name:
- J/A+A/384/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep wide field H{alpha} imaging survey of the central regions of the two nearby clusters of galaxies Coma and Abell 1367, taken with the WFC at the Prime Focus at the NT 2.5m telescope located at Observatorio de El Roque de los Muchachos (La Palma), on April 26th and 28th 2000. We determine for the first time the Schechter parameters of the H{alpha} luminosity function (LF) of cluster galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/546/A77
- Title:
- H{alpha} images of HD93521
- Short Name:
- J/A+A/546/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Owing to its unusual location and its isolation, the nature of the high Galactic latitude O9.5 Vp object HD 93521 is still uncertain. We have collected X-ray and optical observations to characterize the star and its surroundings.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A46
- Title:
- Halpha images of 6 lenticular galaxies
- Short Name:
- J/A+A/659/A46
- Date:
- 04 Mar 2022 00:51:50
- Publisher:
- CDS
- Description:
- As part of the Virgo Cluster Survey Tracing Ionised Gas Emission, a blind narrow-band H{alpha}+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT, we discovered eight massive (10^10^<~M_star_<~10^11^M_{sun}_) lenticular galaxies with prominent ionised gas emission features in their inner (a few kiloparsec) regions. These features are either ionised gas filaments similar to those observed in cooling flows (two galaxies), or they are thin discs with sizes 0.7<~R(H{alpha})<~2.0kpc (six galaxies), thus significantly smaller than those of the stellar disc (R(H{alpha})~=7-22%R_iso_(r)). The morphological properties of these discs are similar to those of the dust seen in absorption in high-resolution HST images. Using a unique set of multifrequency data, including new or archival ASTROSAT/UVIT, GALEX, HST, CFHT, Spitzer, and Herschel imaging data, combined with IFU (MUSE, ALMA) and long-slit (SOAR) spectroscopy, we show that while the gas that is located within these inner discs is photoionised by young stars, which signals ongoing star formation, the gas in the filamentary structures is shock ionised. The star formation surface brightness of these discs is similar to that observed in late-type galaxies. Because of their reduced size, however, these lenticular galaxies are located below the main sequence of unperturbed or cluster star-forming systems. By comparing the dust masses measured from absorption maps in optical images, from the Balmer decrement, or estimated by fitting the UV-to-far-IR spectral energy distribution of the target galaxies, we confirm that the dust masses derived from optical attenuation maps are heavily underestimated because of geometrical effects due to the relative distribution of the absorbing dust and the emitting stars. We also show that these galaxies have gas-to-dust ratios of G/D=~80_30_^320^, and that the star formation within these discs follows the Schmidt relation, but with an efficiency that is reduced by a factor of ~2.5. Using our unique set of multifrequency data, we discuss the possible origin of the ionised gas in these objects, which suggests multiple and complex formation scenarios for massive lenticular galaxies in clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A135
- Title:
- Halpha images of NGC 6334 and NGC 6357
- Short Name:
- J/A+A/587/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the Halpha emission of the star-forming region NGC 6334 and NGC 6357 with the aim to precise/determine the nature of the HII regions.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A38
- Title:
- Halpha images of stellar bars in galaxies
- Short Name:
- J/A+A/644/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar bars are known to gradually funnel gas to the central parts of disk galaxies. It remains a matter of debate why the distribution of ionized gas along bars and in the circumnuclear regions varies among galaxies. Our goal is to investigate the spatial distribution of star formation (SF) within bars of nearby low-inclination disk galaxies (i<65deg) from the S4G survey. We aim to link the loci of SF to global properties of the hosts (morphological type, stellar mass, gas fraction, and bar-induced gravitational torques), providing constraints for the conditions that regulate SF in bars. We use archival GALEX far- and near-UV imaging for 772 barred galaxies, and for a control sample of 423 non-barred galaxies. We also assemble a compilation of continuum-subtracted H{alpha} images for 433 barred galaxies, 70 of which we produced from ancillary photometry and MUSE and CALIFA integral field unit data cubes. We employ two complementary approaches: i) the analysis of bar (2D) and disk (1D) stacks built from co-added UV images (oriented and scaled with respect to the stellar bars and the extent of disks) of hundreds of galaxies that are binned based on their Hubble stage (T) and bar family; and ii) the visual classification of the morphology of ionized regions (traced from H{alpha} and UV data) in individual galaxies into three main SF classes: A) only circumnuclear SF; B) SF at the bar ends, but not along the bar; and C) SF along the bar. Barred galaxies with active and passive inner rings are likewise classified. Massive, gas-poor, lenticular galaxies typically belong to SF class A; this is probably related to bar-induced quenching of SF in the disk. The distribution of SF class B peaks for early- and intermediate-type spirals; this most likely results from the interplay of gas flow, shocks, and enhanced shear in massive centrally concentrated galaxies with large bar amplitudes (the latter is supported by the lack of a dip in the radial distribution of SF in non-barred galaxies). Late-type gas-rich galaxies with high gravitational torques are mainly assigned to SF class C; we argue that this is a consequence of low shear among the faintest galaxies. In bar stacks of spiral galaxies the UV emission traces the stellar bars and dominates on their leading side, as witnessed in simulations. Among early-type spirals the central UV emission is ~0.5mag brighter in strongly barred galaxies, relative to their weakly barred counterparts; this is probably related to the efficiency of strong bars sweeping the disk gas and triggering central starbursts. On the contrary, in later types the UV emission is stronger at all radii in strongly barred galaxies than in weakly barred and non-barred ones. We also show that the distributions of SF in inner-ringed galaxies are broadly the same in barred and non-barred galaxies, including a UV and H{alpha) deficit in the middle part of the bar; this hints at the effect of resonance rings trapping gas that is no longer funneled inwards. Distinct distributions of SF within bars are reported in galaxies of different morphological types. Star-forming bars are most common among late-type gas-rich galaxies. Bars are important agents in the regulation of SF in disks.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/128/2170
- Title:
- H{alpha} imaging of irregular galaxies
- Short Name:
- J/AJ/128/2170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of H{alpha} imaging of a large sample of irregular galaxies. Our sample includes 94 galaxies with morphological classifications of Im, 26 blue compact dwarfs (BCDs), and 20 Sm systems. The sample spans a large range in galactic parameters, including integrated absolute magnitude (M_V_ of -9 to -19), average surface brightness (20-27mag/arcsec^2^), current star formation activity (0-1.3M_{Sun}_/yr/kpc^2^), and relative gas content (0.02-5M_{Sun}_/LB). The H{alpha} images were used to measure the integrated star formation rates, determine the extents of star formation in the disks, and compare azimuthally averaged radial profiles of current star formation to older starlight.
- 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.
2409. H-alpha in Abell 2390
- ID:
- ivo://CDS.VizieR/J/MNRAS/318/703
- Title:
- H-alpha in Abell 2390
- Short Name:
- J/MNRAS/318/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry is tabulated for 1189 galaxies in 19 OSIS-V (CFHT) images in the direction of the galaxy cluster Abell 2390. The images cover 270 sq. deg., and extend out to the virial radius of the cluster. Three narrow filters are used to determine the flux above the continuum between wavelengths 7897 and 8245 {AA}, corresponding to H-alpha at 0.2033<z<0.2563. The absolute flux values are uncertain by about 30% due to zero point uncertainty; we also tabulate the equivalent width which is independent of this zero point. Only strong emission line cluster members (equivalent width greater than about 50{AA}) are detectable, by design. Galaxies with spectra available from the CNOC survey (Abraham=1996ApJ...471..694A) are identified.
- ID:
- ivo://CDS.VizieR/J/A+A/393/389
- Title:
- H{alpha} in HII regions in spiral galaxies
- Short Name:
- J/A+A/393/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we study long slit spectra in the region of H{alpha} emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected H II regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/H{alpha} ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/H{alpha} ratios measured for disk H II regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of H{alpha} equivalent width.
