- 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.
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Search Results
- 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.
- 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.
- 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/AJ/131/716
- Title:
- H{alpha} scale length in Virgo and field spirals
- Short Name:
- J/AJ/131/716
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The scale lengths of the old stars and ionized gas distributions are compared for similar samples of Virgo Cluster members and field spiral galaxies via H{alpha} and broad R-band surface photometry. While the R-band and H{alpha} scale lengths are, on average, comparable for the combined sample, we find significant differences between the field and cluster samples. While the H{alpha} scale lengths of the field galaxies are a factor of 1.14+/-0.07 longer, on average, than their R-band scale lengths, the H{alpha} scale lengths of Virgo Cluster members are, on average, 20% smaller than their R-band scale lengths.
- 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.
- 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.
