Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30 m

Díaz-García, Simón; Lisenfeld, U.; Pérez, I.; Zurita, A.; Verley, S.; Combes, F.; Espada, Daniel; Léon, S.; Martínez-Badenes, Vicent; Sabater, J.; Verdes–Montenegro, L.

doi:10.1051/0004-6361/202140674

Cited by 11 publications

(14 citation statements)

References 198 publications

(251 reference statements)

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“…In barred galaxies, the radial dependence is not monotonic because R 21 is elevated around bar ends, where star formation is active (Muraoka et al 2016;Maeda et al 2020;Koda et al 2020). Díaz-García et al (2021) did not find a clear correlation between R 21 and SFR, but it is at least partially due to different beam sizes and thus to a possible overestimation of the intrinsic ratio. In addition to the variation within a galaxy, R 21 differs among galaxies.…”

Section: Introductionmentioning

confidence: 71%

CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365

Egusa¹,

Gao²,

Morokuma-Matsui³

et al. 2022

ApJ

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We report high-resolution (2″ ∼ 200 pc) mappings of the central region of the nearby barred spiral galaxy NGC 1365 in the CO(1–0) and CO(2–1) emission lines. The 2–1/1–0 ratio of integrated intensities shows a large scatter (0.15) with a median value of 0.67. We also calculate the ratio of velocity dispersions and peak temperatures and find that in most cases the velocity dispersion ratio is close to unity and thus the peak temperature ratio is comparable to the integrated intensity ratio. This result indicates that both CO(1–0) and CO(2–1) lines trace similar components of molecular gas, with their integrated intensity (or peak temperature) ratios reflecting the gas density and/or temperature. Similar to recent kiloparsec-scale studies, these ratios show a positive correlation with a star formation rate indicator (here we use an extinction-corrected Hα map), suggesting that molecular gas associated with recent star formation is denser and/or warmer. We also find that some CO spectra show two peaks owing to complicated kinematics, and such two components likely trace molecular gas at different conditions. This result demonstrates the importance of spectral fitting to measure integrated intensities and their ratios more accurately.

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Section: Introductionmentioning

confidence: 71%

CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365

Egusa¹,

Gao²,

Morokuma-Matsui³

et al. 2022

ApJ

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“…In contrast to the studies that have observed individual barred galaxies, as detailed above, recent statistical studies have suggested that the SFE in the bars is not systematically lower than that in other regions, and that it is, in fact, environmentally independent (e.g., Muraoka et al 2019;Díaz-García et al 2021;Querejeta et al 2021). Muraoka et al (2019) measured the radial variations in the SFEs of 80 galaxies (30 SA, 33 SAB, and 17 SB galaxies) selected from the CO Multi-line Imaging of Nearby Galaxies (COMING) project (Sorai et al 2019).…”

Section: Introductionmentioning

confidence: 75%

“…The authors define the bar parameters by using Spitzer 3.6 μm images. For the galaxies outside the catalog, when available, we adopt the values reported in the literature that were calculated based on near-IR images (Kuno et al 2007;Menendez-Delmestre et al 2007;Díaz-García et al 2021). For galaxies that did not have any corresponding literature, we visually ascertain whether R bar is larger than 37 5; however, no galaxies are visually selected.…”

Section: Nearby Face-on Barred Galaxies With An Apparent Longbar Stru...mentioning

confidence: 99%

Statistical Study of the Star Formation Efficiency in Bars: Is Star Formation Suppressed in Gas-rich Bars?

Maeda

Egusa

Ohta

et al. 2023

ApJ

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The dependence of the star formation efficiency (SFE) on galactic structures—especially whether the SFE in the bar region is lower than those in other regions—has recently been debated. We report the SFEs of 18 nearby gas-rich massive star-forming barred galaxies with large apparent bar major axes (≧75″). We statistically measure the SFE by distinguishing the center, the bar end, and the bar regions for the first time. The molecular gas surface density is derived from archival CO(1–0) and/or CO(2–1) data by assuming a constant CO-to-H2 conversion factor (α CO), and the star formation rate surface density is derived from a linear combination of far-UV and mid-IR intensities. The angular resolution is 15″, which corresponds to 0.3–1.8 kpc. We find that the ratio of the SFE in the bar to that in the disk was systematically lower than unity (typically 0.6–0.8), which means that the star formation in the bar is systematically suppressed. Our results are inconsistent with similar recent statistical studies, which have reported that the SFE tends to be independent of galactic structures. This inconsistency can be attributed to the differences in the definitions of the bar region, the spatial resolutions, the α CO, and the sample galaxies. Furthermore, we find a negative correlation between the SFE and the velocity width of the CO spectrum, which is consistent with the idea that the large dynamical effects—such as strong shocks, large shears, and fast cloud–cloud collisions caused by the noncircular motion of the bar—result in a low SFE.

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“…Barred galaxies may have shorter depletion timescales measured for the whole galaxy (e.g., Géron et al 2021). Still, a recent spatially resolved study found no remarkable differences in the Kennicutt-Schmidt law in the central regions of barred and unbarred galaxies (Díaz-García et al 2021). Strongly barred galaxies do not necessarily have enhanced central star formation rates (SFRs; Wang et al 2012Wang et al , 2020Consolandi et al 2017;Díaz-García et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Strong spiral arms drive secular growth of pseudo bulges in disk galaxies

et al. 2022

A&A

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Spiral-driven instabilities may drive gas inflow to enhance central star formation in disk galaxies. We investigate this hypothesis using the Sloan Digital Sky Survey (SDSS) in a sample of 2779 nearby unbarred star-forming main sequence spiral galaxies. The strength of spiral arms is quantified by their average Fourier amplitude relative to the axisymmetric disk. The star formation properties in the central 1–3 kpc region were derived from the SDSS spectra. We show that galaxies with stronger spiral arms not only tend to have more intense central specific star formation rates (sSFRs), larger Balmer absorption line indices, and lower 4000 Å break strengths, but also have enhanced central sSFRs relative to the sSFR measured for the whole galaxy. This link is independent of redshift, stellar mass, surface density, and concentration. There is a lack of evidence for strong spiral arms being associated with a significant fraction of starburst or post-starburst galaxies, implying that the spiral-induced central star formation is likely continuous rather than bursty. We also show that stronger spiral arms tend to have an increasing fraction of pseudo bulges, a relatively unchanged fraction of star-forming classical bulges, and a decreasing fraction of quenched classical bulges. Moreover, the concentration of galaxies hosting pseudo bulges mildly increases with stronger spiral arms, implying that spirals help pseudo bulges grow. The connection between spirals and bulge type is partly attributed to the suppression of spirals by classical bulges and partly to the enhanced central star formation driven by spirals. We explain our results in the context of a scenario where spiral arms transport cold gas inward to trigger continuous central star formation, which facilitates the buildup of pseudo bulges. Spiral arms thus play a role in the secular evolution of disk galaxies.

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Molecular gas and star formation within 12 strong galactic bars observed with IRAM-30 m

Cited by 11 publications

References 198 publications

CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365

CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365

Statistical Study of the Star Formation Efficiency in Bars: Is Star Formation Suppressed in Gas-rich Bars?

Strong spiral arms drive secular growth of pseudo bulges in disk galaxies

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