VLA Observations of 24 Spiral Galaxies in the Virgo Cluster

Cayatte, V.; Gorkom, Jacqueline van; Balkowski, C.; Kotanyi, C. G.; Guhathakurta, Puragra

doi:10.1007/978-94-009-0903-8_28

Cited by 165 publications

(279 citation statements)

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“…The average H i surface density in the Morganti et al sample is around 1 M ⊙ pc −2 , which is far below the typical value for spiral galaxies (4–8 M ⊙ pc −2 , e.g. Cayatte et al 1994). This would explain why previously only the most gas‐rich early‐type galaxies were detected in H i .…”

Section: Introductionmentioning

confidence: 66%

The shape of the dark matter halo in the early-type galaxy NGC 2974

Weijmans¹,

Krajnović²,

Ven³

et al. 2008

Monthly Notices of the Royal Astronomical Society

100

135

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We present HI observations of the elliptical galaxy NGC 2974, obtained with the Very Large Array. These observations reveal that the previously detected HI disc in this galaxy (Kim et al. 1988) is in fact a ring. By studying the harmonic expansion of the velocity field along the ring, we constrain the elongation of the halo and find that the underlying gravitational potential is consistent with an axisymmetric shape. We construct mass models of NGC 2974 by combining the HI rotation curve with the central kinematics of the ionised gas, obtained with the integral-field spectrograph SAURON. We introduce a new way of correcting the observed velocities of the ionised gas for asymmetric drift, and hereby disentangle the random motions of the gas caused by gravitational interaction from those caused by turbulence. To reproduce the observed flat rotation curve of the HI gas, we need to include a dark halo in our mass models. A pseudo-isothermal sphere provides the best model to fit our data, but we also tested an NFW halo and Modified Newtonian Dynamics (MOND), which fit the data marginally worse. The mass-to-light ratio M/L_I increases in NGC 2974 from 4.3 (M/L_I)sun at one effective radius to 8.5 (M/L_I)sun at 5 Re. This increase of M/L already suggests the presence of dark matter: we find that within 5 Re at least 55 per cent of the total mass is dark.Comment: 17 pages, 20 figures, accepted by MNRA

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Section: Introductionmentioning

confidence: 66%

The shape of the dark matter halo in the early-type galaxy NGC 2974

Weijmans¹,

Krajnović²,

Ven³

et al. 2008

Monthly Notices of the Royal Astronomical Society

100

135

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“…As earlier recognized by Kennicutt (1998), this is a somewhat surprising result, because the typical scales of HI and of star formation are very different in disk galaxies. HI reservoirs extend some 2 × the scale where the star formation takes place (Cayatte et al 1994). We will re-examine this issue in more details in our forthcoming paper dedicated to the morphology of the star formation regions in galaxies, where a comparison between the scale-length of H α , HI and H 2 will be carried on specifically.…”

Section: Discussionmentioning

confidence: 99%

Hα surface photometry of galaxies in the Virgo cluster

Gavazzi¹,

Boselli²,

Pedotti³

et al. 2002

A&A

113

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Hα+[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 (m p < 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 (Θ). The expected decrease of the star formation rate (SFR), as traced by the Hα EW, with decreasing Θ is found only when galaxies brighter than M p ∼ −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. For the isolated objects we find that b decreases with increasing NIR luminosity. In other words less massive galaxies are currently forming stars at a higher rate than their giant counterparts which experienced most of their star formation activity at earlier cosmological epochs. The gas-deficient objects, primarily members of the Virgo cluster, have a birthrate significantly lower than the isolated objects with normal gas content and of similar NIR luminosity. This indicates that the current star formation is regulated by the gaseous content of spirals. Whatever mechanism (most plausibly ram-pressure stripping) is responsible for the pattern of gas deficiency observed in spiral galaxies members of rich clusters, it also produces the observed quenching of the current star formation. A significant fraction of gas "healthy" (i.e. with a gas deficiency parameter less than 0.4) and currently star forming galaxies is unexpectedly found projected near the center of the Virgo cluster. Their average Tully-Fisher distance is found approximately one magnitude further away (µ o = 31.77) than the distance of their gas-deficient counterparts (µ o = 30.85), suggesting that the gas healthy objects belong to a cloud projected onto the cluster center, but in fact lying a few Mpc behind Virgo, thus unaffected by the dense IGM of the cluster.

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“…NGC 4569 can be considered as the prototype of H i ‐deficient galaxy having only about one‐tenth of the atomic gas of a comparable field galaxy of similar type and size. This galaxy has a truncated Hα and H i radial profile (at a radius of ∼5 kpc, Cayatte et al 1994; Koopmann & Kenney 2004; Boselli et al 2006) and shows significant colour gradients with star formation activity only in the central 5 kpc. Therefore, given its significant age gradients, the contribution of UV photons to the dust heating probably varies with the distance from the galaxy centre, making this object ideal to compare with our recipes with age‐independent techniques.…”

Section: Implications On the Study Of Uv Properties Of Galaxiesmentioning

confidence: 99%

Ultraviolet dust attenuation in star-forming galaxies – II. Calibrating the A(UV) versus L_TIR/L_UVrelation

Cortese

Boselli

Franzetti

et al. 2008

Monthly Notices RAS

138

264

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We investigate the dependence of the total-IR (TIR) to ultraviolet (UV) luminosity ratio method for calculating the UV dust attenuation A(UV) from the age of the underlying stellar populations by using a library of spectral energy distributions for galaxies with different star formation histories. Our analysis confirms that the TIR/UV versus A(UV) relation varies significantly with the age of the underlying stellar population: that is, for the same TIR/UV ratio, systems with low specific star formation rate (SSFR) suffer a lower UV attenuation than starbursts. Using a sample of nearby field and cluster spiral galaxies, we show that the use of a standard (i.e. age-independent) TIR/UV versus A(UV) relation leads to a systematic overestimate up to 2 mag of the amount of UV dust attenuation suffered by objects with low SSFR and in particular H I-deficient star-forming cluster galaxies. This result points out that the ageindependent TIR/UV versus A(UV) relation cannot be used to study the UV properties of large samples of galaxies including low star-forming systems and passive spirals. Therefore, we give some simple empirical relations from which the UV attenuation can be estimated taking into account its dependence on the age of the stellar populations, providing a less biased view of UV properties of galaxies.Key words: galaxies: evolution -galaxies: fundamental parameters -galaxies: generalultraviolet: galaxies. I N T RO D U C T I O NThe use of ultraviolet (UV) emission to shed light on the evolutionary history of galaxies is not straightforward. The presence of dust in galaxies represents one of the major obstacles complicating a direct quantification of the star formation activity in local and highredshift galaxies. Absorption by dust grains reddens the spectra at short wavelengths completely modifying the spectral energy distribution (SED) of galaxies. Since the UV radiation is preferentially emitted by young stars that are generally more affected by attenuation from surrounding dust clouds than older stellar populations, rest-frame UV observations can lead to incomplete and/or biased reconstructions of the star formation activity and star formation history (SFH) of galaxies affected by dust absorption, unless proper corrections are applied.Radiative transfer models suggest that the total-IR (TIR) to UV luminosity ratio method (i.e.

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VLA Observations of 24 Spiral Galaxies in the Virgo Cluster

Cited by 165 publications

References 0 publications

The shape of the dark matter halo in the early-type galaxy NGC 2974

The shape of the dark matter halo in the early-type galaxy NGC 2974

Hα surface photometry of galaxies in the Virgo cluster

Ultraviolet dust attenuation in star-forming galaxies – II. Calibrating the A(UV) versus L_TIR/L_UVrelation

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VLA Observations of 24 Spiral Galaxies in the Virgo Cluster

Cited by 165 publications

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The shape of the dark matter halo in the early-type galaxy NGC 2974

The shape of the dark matter halo in the early-type galaxy NGC 2974

Hα surface photometry of galaxies in the Virgo cluster

Ultraviolet dust attenuation in star-forming galaxies – II. Calibrating the A(UV) versus LTIR/LUVrelation

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Ultraviolet dust attenuation in star-forming galaxies – II. Calibrating the A(UV) versus L_TIR/L_UVrelation