ALMA Observations toward the Starburst Dwarf Galaxy NGC 5253. I. Molecular Cloud Properties and Scaling Relations

Miura, Rie; Espada, Daniel; Hirota, Akihiko; Nakanishi, Koichiro; Bendo, G. J.; Sugai, Hajime

doi:10.3847/1538-4357/aad69f

Cited by 23 publications

(22 citation statements)

References 80 publications

(182 reference statements)

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“…Another interesting fact is that most clumps in M17-IRDC live above the SVE line which mean they need additional external pressure to collapse while those in M17-HII do not. This fact is consistent with the higher virial parameters in M17-IRDC clumps and also consistent with what found in molecular clouds in the Galactic Center (Miura et al 2018).…”

Section: Stability Of Clumps In M17-irdc and M17-hiisupporting

confidence: 92%

Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

Nguyen-Luong

Nakamura

Sugitani

et al. 2020

ApJ

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The non-uniform distribution of gas and protostars in molecular clouds is caused by combinations of various physical processes that are difficult to separate. We explore this non-uniform distribution in the M17 molecular cloud complex that hosts massive star formation activity using the 12 CO (J = 1−0) and 13 CO (J = 1 − 0) emission lines obtained with the Nobeyama 45m telescope. Differences in clump properties such as mass, size, and gravitational boundedness reflect the different evolutionary stages of the M17-HII and M17-IRDC clouds. Clumps in the M17-HII cloud are denser, more compact, and more gravitationally bound than those in M17-IRDC. While M17-HII hosts a large fraction of very dense gas (27%) that has column density larger than the threshold of ∼ 1 g cm −2 theoretically predicted for massive star formation, this very dense gas is deficient in M17-IRDC (0.46%). Our HCO + (J = 1 − 0) and HCN (J = 1 − 0) observations with the TRAO 14m telescope, trace all gas with column density higher than 3 × 10 22 cm −2 , confirm the deficiency of high density ( 10 5 cm −3 ) gas in M17-IRDC.Although M17-IRDC is massive enough to potentially form massive stars, its deficiency of very dense gas and gravitationally bound clumps can explain the current lack of massive star formation.

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Section: Stability Of Clumps In M17-irdc and M17-hiisupporting

confidence: 92%

Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

Nguyen-Luong

Nakamura

Sugitani

et al. 2020

ApJ

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“…If an island has a projected area of less than two synthesised beams, it is assumed to be a noise peak and is removed from the mask. The resulting mask contains ≈ 60% of the integrated flux of the galaxy, consistent with the fractions yielded by CPROPS in other studies of extragalactic clouds (50 -70%; Wong et al 2011;Hughes et al 2013;Donovan Meyer et al 2013;Colombo et al 2014;Leroy et al 2015;Pan & Kuno 2017;Miura et al 2018;Faesi et al 2018;Wong et al 2019;Imara & Faesi 2019). We checked the stringency of the mask by applying the same criteria to the inverted data set (scaled by −1) and found no false positive, so the masking criteria are likely robust.…”

Section: Cloud Identificationsupporting

confidence: 80%

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

Liu

Bureau

Blitz

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present high spatial resolution (≈12 pc) Atacama Large Millimeter/sub-millimeter Array 12CO(J = 3 − 2) observations of the nearby lenticular galaxy NGC4429. We identify 217 giant molecular clouds within the 450 pc radius molecular gas disc. The clouds generally have smaller sizes and masses but higher surface densities and observed linewidths than those of Milky Way disc clouds. An unusually steep size – line width relation ($\sigma \propto R_{\rm c}^{0.8}$) and large cloud internal velocity gradients (0.05 – 0.91 km s−1 pc−1) and observed Virial parameters (〈αobs, vir〉 ≈ 4.0) are found, that appear due to internal rotation driven by the background galactic gravitational potential. Removing this rotation, an internal Virial equilibrium appears to be established between the self-gravitational (Usg) and turbulent kinetic (Eturb) energies of each cloud, i.e. $\langle \alpha _{\rm sg,vir}\equiv \frac{2E_{\rm turb}}{\vert U_{\rm sg}\vert }\rangle \approx 1.3$. However, to properly account for both self and external gravity (shear and tidal forces), we formulate a modified Virial theorem and define an effective Virial parameter $\alpha _{\rm eff,vir}\equiv \alpha _{\rm sg,vir}+\frac{E_{\rm ext}}{\vert U_{\rm sg}\vert }$ (and associated effective velocity dispersion). The NGC4429 clouds then appear to be in a critical state in which the self-gravitational energy and the contribution of external gravity to the cloud’s energy budget (Eext) are approximately equal, i.e. $\frac{E_{\rm ext}}{\vert U_{\rm sg}\vert }\approx 1$. As such, 〈αeff, vir〉 ≈ 2.2 and most clouds are not virialised but remain marginally gravitationally bound. We show this is consistent with the clouds having sizes similar to their tidal radii and being generally radially elongated. External gravity is thus as important as self-gravity to regulate the clouds of NGC4429.

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“…In addition, shadowing of the diffuse X-ray emission by the cooler disk gas (Ott et al 2005) may suggest that the radial motions are an inflow. A similar conclusion was reached by Miura et al (2018) analyzing CO(21) observations taken with ALMA. López-Sánchez et al (2012) analyzed deep HI data proposing that the very peculiar HI morphology and kinematics of NGC 5253 could be explained by an interaction scenario.…”

Section: Sf Spatial Patternssupporting

confidence: 77%

Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies*

Cignoni

Sacchi

Tosi

et al. 2019

ApJ

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We derive the recent star formation histories of 23 active dwarf galaxies using HST observations from the Legacy Extragalactic UV Survey (LEGUS). We apply a color-magnitude diagram fitting technique using two independent sets of stellar models, PARSEC-COLIBRI and MIST. Despite the non-negligible recent activity, none of the 23 star forming dwarfs show enhancements in the last 100 Myr larger than three times the 100-Myr-average. The unweighted mean of the individual SFHs in the last 100 Myr is also consistent with a rather constant activity, irrespective of the atomic gas fraction. We confirm previous results that for dwarf galaxies the CMD-based average star formation rates (SFRs) are generally higher than the FUV-based SFR. For half of the sample, the 60-Myr-average CMD-based SFR is more than two times the FUV SFR. In contrast, we find remarkable agreement between the 10-Myr-average CMD-based SFR and the Hα-based SFR. Finally, using core helium burning stars of intermediate mass we study the pattern of star formation spatial progression over the past 60 Myr, and speculate on the possible triggers and connections of the star formation activity with the environment in which these galaxies live. Approximately half of our galaxies show spatial progression of star formation in the last 60 Myr, and/or very recent diffuse and off-center activity compared to RGB stars.

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ALMA Observations toward the Starburst Dwarf Galaxy NGC 5253. I. Molecular Cloud Properties and Scaling Relations

Cited by 23 publications

References 80 publications

Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies*

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