- ID:
- ivo://CDS.VizieR/J/ApJ/677/169
- Title:
- H{alpha} galaxies at z=0.84
- Short Name:
- J/ApJ/677/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an H{alpha} near-infrared narrowband survey searching for star-forming galaxies at redshift z=0.84. This work is an extension of our previous narrowband studies in the optical at lower redshifts. After removal of stars and redshift interlopers (using spectroscopic and photometric redshifts), we build a complete sample of 165 H{alpha} emitters in the extended Groth strip and GOODS-N fields with L(H{alpha})>10^41^ergs/s. We compute the H{alpha} luminosity function at z=0.84 after corrections for [NII] flux contamination, extinction, systematic errors, and incompleteness. Our sources present an average dust extinction of A(H{alpha})=1.5mag. Adopting H{alpha} as a surrogate for the instantaneous SFR, we measure an extinction-corrected SFR density of 0.17^+0.03^_-0.03_M_{sun}_/yr/Mpc^3^. Combining this result to our prior measurements at z=0.02, 0.24, and 0.40, we derive an H{alpha}-based evolution of the SFR density proportional to (1+z)^{beta}^ with {beta}=3.8+/-0.5. This evolution is consistent with that derived by other authors using different SFR tracers.
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Search Results
- 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.
1396. Halpha maps of 3 LIRGS
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3461
- Title:
- Halpha maps of 3 LIRGS
- Short Name:
- J/MNRAS/465/3461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed three luminous infrared galaxy systems (LIRGS) which are pairs of interacting galaxies, with the Galaxy H{alpha} Fabry-Perot system (GH{alpha}FaS) mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array (ALMA) observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star forming regions. We identified 88 star forming regions in the H$\alpha$ emission data-cubes, and 27 molecular cloud complexes in the CO emission data-cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star forming galaxies at higher redshifts. The large values of the velocity dispersion also show the enhanced gas surface density. The HII regions are situated on the {Sigma}_SFR_-{sigma}_v_ envelope, and so are also in virial equilibrium. Since the virial parameter decreases with the surface densities of both the star formation rate and the molecular gas, we claim that the clouds presented here are gravitationally dominated rather than being in equilibrium with the external pressure.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A176
- Title:
- Halpha+[NII] imaging of Dorado galaxies
- Short Name:
- J/A+A/643/A176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the Southern Hemisphere. Although several studies have been dedicated to define its members, their kinematics, hot and cold gas content, in particular HI, their present star formation activity is yet unknown. For the first time, we map the H{alpha} distribution as a possible indicator of star formation activity of Dorado members a large fraction of which show interaction and merging signatures, regardless of their morphological type. With the 2.5m du Pont and the 1m Swope telescopes we obtained narrow-band, calibrated images of 14 galaxies, forming the backbone of the group, mapping H{alpha}+[NII] down to few 10^-17^erg/cm^2^/s/arcsec^2^. We estimated the galaxy star formation rate from the H{alpha} fluxes, corrected for Galaxy foreground extinction and [NII] contamination. H{alpha}+[NII] emission has been detected in all galaxies. HII regions clearly emerge in late-type galaxies, while in early-type galaxies the H{alpha}+[NII] emission is dominated by [NII], especially in the central regions. However, HII complexes are revealed in four early-type galaxies. Even in the compact group SGC 0414-5559, in the projected centre of Dorado, HII regions are found both through out the late-type galaxies and in the very outskirts of early-type members. Considering the Dorado group as a whole, we notice that the H{alpha}+[NII] equivalent width, a measure of the specific star formation, increases with the morphological type, from early to late-type members, although it remains lower that what observed in similar surveys of spiral galaxies. The star formation rate of the spiral members is in the range of what observed in similar galaxies surveys (James et al., 2004A&A...414...23J, Cat. J/A+A/414/23). However, in three spiral NGC 1536, PGC 75125 and IC 2058 the star formation rate is well below the median for their morphological classes. The star formation rate of some early-type members tends, at odds, to be higher than the average derived from H{alpha}+[NII] surveys of this morphological family. We detected in H{alpha}+[NII] all the early type galaxies observed and half of them show HII regions in well shaped rings as well as in their outskirts. These findings suggest that ETGs in this group are not dead galaxies: their star formation has not shutdown yet. Mechanisms such as gas stripping and gas accretion, through galaxy-galaxy interaction, seem relevant in modifying star formation in this evolutionary phase of Dorado.
- 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/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.
