Discovery of kpc-scale line emission in barred galaxies, not linked to AGN or star formation.

James, P. A.; Percival, S. M.

doi:10.1093/mnras/stv846

Cited by 23 publications

(39 citation statements)

References 25 publications

(25 reference statements)

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“…This study confirmed the complete suppression of SF within the SFD region in these 4 galaxies; while some low-level diffuse line emission was detected, this showed line ratios and a smooth spatial distribution that can be much more naturally explained by an old stellar population, e.g. post-AGB stars (James & Percival 2015); see also Stasińska et al (2008), Sarzi et al (2010), Yan & Blanton (2012) and Bremer et al (2013). After correcting for this weak line emission, we fitted the remaining absorption-line spectra by a model that assumed an initially constant SF rate, followed by a sharp truncation in SF activity; the one free parameter in the model was the epoch at which this truncation occurred.…”

Section: Stellar Populations In Star Formation Desert Regionssupporting

confidence: 81%

Star formation suppression and bar ages in nearby barred galaxies

James

Percival

2017

Monthly Notices of the Royal Astronomical Society

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We present new spectroscopic data for 21 barred spiral galaxies, which we use to explore the effect of bars on disk star formation, and to place constraints on the characteristic lifetimes of bar episodes. The analysis centres on regions of heavily suppressed star formation activity, which we term 'star formation deserts'. Long-slit optical spectroscopy is used to determine Hβ absorption strengths in these desert regions, and comparisons with theoretical stellar population models are used to determine the time since the last significant star formation activity, and hence the ages of the bars. We find typical ages of ∼1 Gyr, but with a broad range, much larger than would be expected from measurement errors alone, extending from ∼0.25 Gyr to >4 Gyr. Low-level residual star formation, or mixing of stars from outside the 'desert' regions, could result in a doubling of these age estimates. The relatively young ages of the underlying populations coupled with the strong limits on the current star formation rule out a gradual exponential decline in activity, and hence support our assumption of an abrupt truncation event.

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Section: Stellar Populations In Star Formation Desert Regionssupporting

confidence: 81%

Star formation suppression and bar ages in nearby barred galaxies

James

Percival

2017

Monthly Notices of the Royal Astronomical Society

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“…Long-slit spectroscopy of the bar-region showed a diffused emission which are not found to be associated with star formation. They attribute this emission to be due to post Asymptotic Giant Branch (p-AGB) stars (James & Percival 2015). These studies suggest that the observed nuclear star burst and suppression of recent star formation (∼ 10 Myr) in the bar-region is due to the effect of bar.…”

Section: Introductionmentioning

confidence: 91%

Insights on bar quenching from a multiwavelength analysis: The case of Messier 95

George

Joseph

Mondal

et al. 2019

A&A

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The physical processes related to the effect of bar in the quenching of star formation in the region between the nuclear/central sub-kpc region and the ends of the bar (bar-region) of spiral galaxies is not fully understood. It is hypothesized that the bar can either stabilize the gas against collapse, inhibiting star formation or efficiently consume all the available gas, with no fuel for further star formation. We present a multi-wavelength study using the archival data of an early-type barred spiral galaxy, Messier 95, which shows signatures of suppressed star formation in the bar-region. Using the optical, ultraviolet, infrared, CO and HI imaging data we study the pattern of star formation progression, stellar/gas distribution and try to provide insights on the process responsible for the observed pattern. The FUV-NUV pixel colour map reveals a cavity devoid of UV flux in the bar-region that interestingly matches with the length of the bar (∼ 4.2 kpc). The central nuclear region of the galaxy is showing a blue color clump and along the major-axis of the stellar bar the colour progressively becomes redder. Based on a comparison to single stellar population models, we show that the region of galaxy along the major-axis of the bar (unlike the region outside the bar) is comprised of stellar populations with ages ≥ 350 Myr, with a star-forming clump in the center of younger ages (∼ 150Myr). Interestingly the bar-region is also devoid of neutral and molecular hydrogen but with an abundant molecular hydrogen present at the nuclear region of the galaxy. Our results are consistent with a picture in which the stellar bar in Messier 95 is redistributing the gas by funneling gas inflows to nuclear region, thus making the bar-region devoid of fuel for star formation.

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“…Thus, we suggest here a complementary technique, based on the influence of the bar on the star formation (SF) activity in its surrounding environment, rather than within the bar itself. This paper builds on the results of a recent Hα spectroscopic study of 15 nearby barred galaxies (James & Percival 2015, henceforth JP15). These galaxies had previously been identified (James, Bretherton, & Knapen 2009) as having a specific pattern of emission in continuum-subtracted narrow-band Hα imaging, with a pronounced dip in this emission in the radial range swept out by the bar.…”

Section: Introductionmentioning

confidence: 98%

Stellar population constraints on the ages of galactic bars

James

Percival

2016

Mon. Not. R. Astron. Soc.

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We present a study of the stellar populations within the central regions of four nearby barred galaxies, and use a novel technique to constrain the duration of bar activity. We focus on the star formation 'desert', a region within each of these galaxies where star formation appears to have been suppressed by the bar. New Hβ spectroscopic data are presented, and used to produce spectroscopic line indices which are compared with theoretical predictions from population synthesis models for simple stellar populations and temporally truncated star formation histories. This analysis shows that the dearth of star formation activity in these regions appears to have been continuing for at least 1 Gyr, with timescales of several Gyr indicated for two of the galaxies. This favours models in which strong bars can be long-lived features of galaxies, but our results also indicate a significant diversity in stellar population ages, and hence in the implied histories of bar activity in these four galaxies.

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Discovery of kpc-scale line emission in barred galaxies, not linked to AGN or star formation.

Cited by 23 publications

References 25 publications

Star formation suppression and bar ages in nearby barred galaxies

Star formation suppression and bar ages in nearby barred galaxies

Insights on bar quenching from a multiwavelength analysis: The case of Messier 95

Stellar population constraints on the ages of galactic bars

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