EMPIRE: The IRAM 30 m Dense Gas Survey of Nearby Galaxies

Jiménez-Donaire, María J.; Bigiel, Frank; Leroy, Adam K.; Usero, A.; Cormier, D.; Puschnig, Johannes; Gallagher, Molly; Kepley, Amanda A.; Bolatto, Alberto D.; García‐Burillo, S.; Hughes, Annie; Krämer, C.; Pety, J.; Schinnerer, E.; Schruba, Andreas; Schuster, K.; Walter, Fabian

doi:10.3847/1538-4357/ab2b95

Cited by 119 publications

(165 citation statements)

References 138 publications

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“…With regard to the relationship between SFE dense and Σ stellar , previous studies using the J = 1 − 0 transition of HCN and/or HCO + all showed anti-correlations (Usero et al 2015;Gallagher et al 2018a;Jiménez-Donaire et al 2019), so it is somewhat surprising to see an increasing trend between SFE dense and Σ stellar in Fig. 11b.…”

Section: The Relationships Between Star-formation Efficiency Dense-gmentioning

confidence: 83%

“…11 our statistics only include data points with SNR > 3. However, their latest result based on a larger sample shows more promising trends (Jiménez-Donaire et al 2019), so the difference is more likely a physical effect. The inconsistency implies the possibly different effects of Σ stellar on HCN 4-3 and HCO + 4-3.…”

Section: The Relationships Between Star-formation Efficiency Dense-gmentioning

confidence: 99%

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The MALATANG survey: dense gas and star formation from high-transition HCN and HCO+ maps of NGC 253

Jiang

Greve

Gao

et al. 2020

Monthly Notices of the Royal Astronomical Society

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To study the high-transition dense-gas tracers and their relationships to the star formation of the inner ∼ 2 kpc circumnuclear region of NGC 253, we present HCN J = 4 − 3 and HCO + J = 4 − 3 maps obtained with the James Clerk Maxwell Telescope (JCMT). With the spatially resolved data, we compute the concentration indices r 90 /r 50 for the different tracers. HCN and HCO + 4-3 emission features tend to be centrally concentrated, which is in contrast to the shallower distribution of CO 1-0 and the stellar component. The dense-gas fraction ( f dense , traced by the velocity-integratedintensity ratios of HCN/CO and HCO + /CO) and the ratio R 31 (CO 3-2/1-0) decline towards larger galactocentric distances, but increase with higher SFR surface density. The radial variation and the large scatter of f dense and R 31 imply distinct physical conditions in different regions of the galactic disc. The relationships of f dense versus Σ stellar , and SFE dense versus Σ stellar are explored. SFE dense increases with higher Σ stellar in this galaxy, which is inconsistent with previous work that used HCN 1-0 data. This implies that existing stellar components might have different effects on the high-J HCN and HCO + than their low-J emission. We also find that SFE dense seems to be decreasing with higher f dense which is consistent with previous works, and it suggests that the ability of the dense gas to form stars diminishes when the average density of the gas increases. This is expected in a scenario where only the regions with high-density contrast collapse and form stars.

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Section: The Relationships Between Star-formation Efficiency Dense-gmentioning

confidence: 83%

Section: The Relationships Between Star-formation Efficiency Dense-gmentioning

confidence: 99%

The MALATANG survey: dense gas and star formation from high-transition HCN and HCO+ maps of NGC 253

Jiang

Greve

Gao

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…At the same time as SFE dense decreases with increasing Σ H2 (as explored in § 4.2.2), the dense gas fraction f d is observed to increase ∝ Σ 1/2 H2 (U15; Bigiel et al 2016;Gallagher et al 2018a). This empirical trend has been associated with a dependence of the dense gas fraction on pressure in the ambient ISM (Usero et al 2015;Meidt 2016;Gallagher et al 2018a;Jiménez-Donaire et al 2019), which is empirically linked to the H 2 -to-HI ratio. As a result of these nearly reverse dependencies, our model predicts that the SFR per unit molecular gas mass is maintained at a roughly constant level, independent of Σ H2 (Usero et al 2015).…”

Section: Discussionmentioning

confidence: 98%

A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces. II. The Bottleneck to Collapse Set by Cloud–Environment Decoupling

Meidt

Glover

Kruijssen

et al. 2020

ApJ

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In Meidt et al. (2018), we showed that gas kinematics on the scale of individual molecular clouds are not dominated by self-gravity but also track a component that originates with orbital motion in the potential of the host galaxy. This agrees with observed cloud line widths, which show systematic variations from virial motions with environment, pointing at the influence of the galaxy potential. In this paper, we hypothesize that these motions act to slow down the collapse of gas and so help regulate star formation. Extending the results of Meidt et al. (2018), we derive a dynamical collapse timescale that approaches the free-fall time only once the gas has fully decoupled from the galactic potential. Using this timescale we make predictions for how the fraction of free-falling, strongly self-gravitating gas varies throughout the disks of star-forming galaxies. We also use this collapse timescale to predict variations in the molecular gas star formation efficiency, which is lowered from a maximum, feedback-regulated level in the presence of strong coupling to the galactic potential. Our model implies that gas can only decouple from the galaxy to collapse and efficiently form stars deep within clouds. We show that this naturally explains the observed drop in star formation rate per unit gas mass in the Milky Way's CMZ and other galaxy centers. The model for a galactic bottleneck to star formation also agrees well with resolved observations of dense gas and star formation in galaxy disks and the properties of local clouds.

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“…Bigiel et al 2008;Leroy et al 2008;Schruba et al 2011), as well as the molecular gas main sequence relation between Σ and Σ H 2 (Wong et al 2013;Lin et al 2019). The availabilty of dense gas (as traced by HCN) maps for small samples of galaxies reveals additional kpc-scale dependences, such a positive correlation between the dense gas fraction and Σ (Usero et al 2015;Bigiel et al 2016;Gallagher et al 2018;Jimenez-Donaire et al 2019).…”

Section: Introductionmentioning

confidence: 95%

“…Likewise, although SFR correlates well with dense molecular gas mass on scales from molecular clouds to galaxies (e.g. Gao & Solomon 2004;Wu et al 2005;Lada et al 2010), the significant scatter in this relation, and anti-correlation of the star formation efficiency of dense gas on Σ , point to local environmental regulation of star formation (Usero et al 2015;Bigiel et al 2016;Gallagher et al 2018;Jimenez-Donaire et al 2019). As a result, there is significant galaxy-to-galaxy variation of the rSFMS and the SFE can vary by an order of magnitude or more within a given galaxy (e.g.…”

Section: Introductionmentioning

confidence: 98%

The ALMaQUEST Survey – II. What drives central starbursts at z ∼ 0?

Ellison

Thorp

Pan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Starburst galaxies have elevated star formation rates (SFRs) for their stellar mass. In Ellison et al. (2018) we used integral field unit (IFU) maps of star formation rate surface density (Σ SFR ) and stellar mass surface density (Σ ) to show that starburst galaxies in the local universe are driven by SFRs that are preferentially boosted in their central regions. Here, we present molecular gas maps obtained with the Atacama Large Millimeter Array (ALMA) observatory for 12 central starburst galaxies at z ∼ 0 drawn from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The ALMA and MaNGA data are well matched in spatial resolution, such that the ALMA maps of molecular gas surface density (Σ H 2 ) can be directly compared with MaNGA maps at kpc-scale resolution. The combination of Σ H 2 , Σ and Σ SFR at the same resolution allow us to investigate whether central starbursts are driven primarily by enhancements in star formation efficiency (SFE) or by increased gas fractions. By computing offsets from the resolved Kennicutt-Schmidt relation (Σ H 2 vs. Σ SFR ) and the molecular gas main sequence (Σ vs. Σ H 2 ), we conclude that the primary driver of the central starburst is an elevated SFE. We also show that the enhancement in Σ SFR is accompanied by a dilution in O/H, consistent with a triggering that is induced by metal poor gas inflow. These observational signatures are found in both undisturbed (9/12 galaxies in our sample) and recently merged galaxies, indicating that both interactions and secular mechanisms contribute to central starbursts.

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EMPIRE: The IRAM 30 m Dense Gas Survey of Nearby Galaxies

Cited by 119 publications

References 138 publications

The MALATANG survey: dense gas and star formation from high-transition HCN and HCO+ maps of NGC 253

The MALATANG survey: dense gas and star formation from high-transition HCN and HCO+ maps of NGC 253

A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces. II. The Bottleneck to Collapse Set by Cloud–Environment Decoupling

The ALMaQUEST Survey – II. What drives central starbursts at z ∼ 0?

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