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

Abstract

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.

The central region of the enigmatic Malin 1

“…The broad-band colours and the central strong emission lines such as Ha and [OII] suggest mixed stellar population with very young stars. Contrary to quenching due to the bar (George et al 2019), we see rejuvenation of the bar (Barway & Saha 2020) probably induced by the companion galaxies but this remains to be investigated with more detailed IFU-like observation. Overall, it appears that the gigantic Malin 1 has a massive Milky Way size stellar disk at its heart.…”

“…It can funnel gas inwards (Combes 2004) and ignite starformation activity in the central region of a galaxy and lead to the formation of a pseudobulge (Athanassoula 1992;Kormendy & Kennicutt 2004;Jogee et al 2005;Lin et al 2017). On the other hand, a bar can also lead to the star-formation quenching (James et al 2009;James & Percival 2016;Khoperskov et al 2018;George et al 2019George et al , 2020. The bar in Malin 1 has induced star-formation, probably due to the ongoing interaction; especially due to the in-spiraling Malin 1B.…”

Redistribution of stars and gas in the star formation deserts of barred galaxies

“…The global distribution of gas in the central regions also appears to be consistent with observations. In particular the absence of gas within SFDs is clear in the ALMA observations of molecular gas shown by George et al (2019).…”

Galaxy Zoo: 3D – crowdsourced bar, spiral, and foreground star masks for MaNGA target galaxies

“…Since the strong correlation between optical colour (as an indicator of quenching) and bar fractions was first noted (Masters et al 2011) there has been significant interest in the role bars may play in the quenching of star formation in disc galaxies (e.g. Masters et al 2012;Gavazzi et al 2015;Khoperskov et al 2018;Kruk et al 2018;George et al 2019;Maeda et al 2020). Even before this, the role of bars in radial mixing (and corresponding impact on radial gradients) had been much debated (see Zurita et al 2021a, b for a discussion of the history of this topic).…”