The Cool ISM in S0 Galaxies. II. A Survey of Atomic Gas

Sage, Leslie J.; Welch, Gary A.

doi:10.1086/503597

Cited by 60 publications

(103 citation statements)

References 32 publications

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“…Since the timescale of this phase is about 10 −3 t H , the mass of the cool ISM is expected to be < ∼ 10 −3 times the mass returned during t H . This is indeed consistent with what was found for the most gas-poor S0 galaxies by Sage & Welch (2006). To check this idea further, we searched for a correlation between the relative (i.e., observed versus predicted) gas mass and the presence of dust in the centres of S0 galaxies.…”

Section: Discussion: the Dust In The Central Region Of Ngc 3384supporting

confidence: 84%

“…Many galaxies have peak CO emission in the centre (Regan et al 2001;Helfer et al 2003) and molecular gas is known to be more centrally concentrated in galaxies with bars (Seth et al 2005). For the most gas-poor S0 galaxies studied by Sage & Welch (2006), the cool gas is dominated by the molecular phase which seems to be concentrated towards the galaxy centres while the neutral gas is probably more widely distributed. A median size of the CO-emitting region of 0.7 kpc has been derived by Welch & Sage (2003).…”

Section: Discussion: the Dust In The Central Region Of Ngc 3384mentioning

confidence: 99%

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The inner structure of the S0 galaxy NGC 3384

Meusinger¹,

Ismail

Notni³

2007

Astron Nachr

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We re-investigate the lenticular galaxy NGC 3384, a member of the Leo I galaxy group, using HST and multi-colour Calar Alto observations. Various approaches are used to visualize the two known peculiar components, the so-called inner component (IC) and the elongated component (EC), on the HST images. The methods were checked in detail using synthetical images from simulated galaxies. For the first time, we make the IC as well as the inner part of the EC visible on direct images. The results confirm both the bar-like appearance of the inner EC and the quasi-elliptical shape of the IC. The IC resembles an inclined disk where the surface brightness becomes successively shallower towards the centre compared to an exponential profile. The orientation of the inner part of the EC is perpendicular to the major axis of the IC. The broad-band colour indices are shown to be in agreement with model predictions for a 5 to 7 Gyr old stellar population of quasi-solar metallicity. No significant large-scale variations of the colour indices over the main body of the galaxy are found. We discuss the previously reported colour gradients close to the nucleus and argue that the most plausible explanation is reddening by small amounts of dust though unsharp masked HST images do not provide significant hints for clumpy dust. According to the episodic dust settling scenario suggested by Lauer et al. (2005), the very low dust fraction indicates that NGC 3384 is in a post-activity phase and at the beginning of a new dust-settling cycle.

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Section: Discussion: the Dust In The Central Region Of Ngc 3384supporting

confidence: 84%

Section: Discussion: the Dust In The Central Region Of Ngc 3384mentioning

confidence: 99%

The inner structure of the S0 galaxy NGC 3384

Meusinger¹,

Ismail

Notni³

2007

Astron Nachr

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“…In both cases our data are definitely of superior quality. As for the undetected ones, 2 objects have in the literature Hi limits worse than those here provided (NGC 3379, 5770), while for NGC 3377 (Knapp et al 1979), NGC 3412 and NGC 4880 (Sage & Welch 2006) the published limits are lower than ours. We do not confirm the dubious detection of NGC 6014 of comparable sensitivity to ours (Lewis 1983).…”

Section: Hi Propertiescontrasting

confidence: 79%

The Hi content of early-type galaxies from the ALFALFA survey

Grossi¹,

Alighieri²,

Giovanardi³

et al. 2009

A&A

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Aims. We present the analysis of the Hi content of a sample of early-type galaxies (ETGs) in low-density environments (LDEs) using the data set provided by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We compare their properties to the sample in the Virgo cluster that we studied in a previous paper (di Serego Alighieri et al. 2007, A&A, 474, 851, Paper I). Our aim is both to investigate how the cool interstellar medium (ISM) of these systems depends on the galaxy mass and the environment and to relate the properties of the neutral hydrogen to the warm phases of the ISM. Methods. We have selected a sample of 62 nearby ETGs (V < 3000 km s −1 ) in an area of the sky where the ALFALFA data are already available (8 h < RA < 16 h , 4 • < Dec < 16 • ), avoiding the region of the Virgo cluster. Among these, 39 have absolute B magnitudes fainter than M B = −17. Results. Fifteen out of 62 galaxies have been firmly detected with ALFALFA (∼25%). Five additional galaxies show a weaker Hi emission (S/N ∼ 4) and they will need deeper observations to be confirmed. Eight objects had 21-cm measurements reported in the literature. One by one comparison with the available material confirms, as expected, that ALFALFA data are, with rare exceptions, of equal or better quality than the best spectra previously obtained for these objects. All together, our analysis doubles the number of known gas-rich ETGs in this area. The Hi detection rate is 44% in luminous ETGs (M B < −17) and 13% in dwarf ETGs (M B > −17). In both cases it is 10 times higher than that of the Virgo cluster. The presence of gas can be related to a recent star formation activity: 60% of all ETGs with Hi have optical emission line ratios typical of star-forming galaxies and blue colours suggesting the presence of young stellar populations, especially in the dwarf subsample. Conclusions. We show that the Hi detection rate of ETGs depends both on the environment and mass. The fraction of early-type systems with neutral hydrogen is higher in more massive objects when compared to early-type dwarfs. The ETGs in LDEs seem to have more heterogeneous properties than their Virgo cluster counterparts, since they are able to retain a cold interstellar gas component and to support star formation activity even at recent epochs.

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“…A potential scenario for creating extended, star-forming disks around early types is external acquisition of extended gas, whether delivered by companion interactions or fresh cosmic gas accretion, and subsequent conversion of this gas to stars. In early-type galaxies, such extended disks or rings of H i are frequently observed and often believed to be associated with external accretion (e.g., Sage & Welch 2006;Morganti et al 2006;Oosterloo et al 2007Oosterloo et al , 2010.…”

Section: Ubiquity Of Xuvs Compared To Uv-bsmentioning

confidence: 99%

Extended Ultraviolet Disks and Ultraviolet-Bright Disks in Low-Mass E/S0 Galaxies

Moffett

Kannappan

Baker

et al. 2011

ApJ

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We have identified 15 extended ultraviolet (XUV) disks in a largely field sample of 38 E/S0 galaxies that have stellar masses primarily below ∼4 × 10 10 M and comparable numbers on the red and blue sequences. We use a new purely quantitative XUV-disk definition designed with reference to the "Type 1" XUV-disk definition found in the literature, requiring UV extension relative to a UV-defined star formation threshold radius. The 39% ± 9% XUV-disk frequency for these E/S0s is roughly twice the ∼20% reported for late-type galaxies (although differences in XUV-disk criteria complicate the comparison), possibly indicating that XUV disks are preferentially associated with galaxies experiencing weak or inefficient star formation. Consistent with this interpretation, we find that the XUV disks in our sample do not correlate with enhanced outer-disk star formation as traced by blue optical outer-disk colors. However, UV-Bright (UV-B) disk galaxies with blue UV colors outside their optical 50% light radii do display enhanced optical outer-disk star formation as well as enhanced atomic gas content. UV-B disks occur in our E/S0s with a 42 +9 −8 % frequency and need not coincide with XUV disks; thus their combined frequency is 61% ± 9%. For both XUV and UV-B disks, UV colors typically imply <1 Gyr ages, and most such disks extend beyond the optical R 25 radius. XUV disks occur over the full sample mass range and on both the red and blue sequences, suggesting an association with galaxy interactions or another similarly general evolutionary process. In contrast, UV-B disks favor the blue sequence and may also prefer low masses, perhaps reflecting the onset of cold-mode gas accretion or another mass-dependent evolutionary process. Virtually all blue E/S0s in the gas-rich regime below stellar mass M t ∼ 5 × 10 9 M (the "gas-richness threshold mass") display UV-B disks, supporting the previously suggested association of this population with active disk growth.

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The Cool ISM in S0 Galaxies. II. A Survey of Atomic Gas

Cited by 60 publications

References 32 publications

The inner structure of the S0 galaxy NGC 3384

The inner structure of the S0 galaxy NGC 3384

The Hi content of early-type galaxies from the ALFALFA survey

Extended Ultraviolet Disks and Ultraviolet-Bright Disks in Low-Mass E/S0 Galaxies

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