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The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy diskHerrera, Cinthya N.Pety, JérômeHughes, AnnieMeidt, Sharon E.Kreckel, KathrynQuerejeta, MiguelSaito, ToshikiLang, PhilippJiménez-Donaire, María JesúsPessa, IsmaelCormier, DianeUsero, AntonioSliwa, KazimierzFaesi, ChristopherBlanc, Guillermo A.Bigiel, FrankChevance, MélanieDale, Daniel A.Grasha, KathrynGlover, Simon C. O.Hygate, Alexander P. S.Kruijssen, J. M. DiederikLeroy, Adam K.Rosolowsky, ErikSchinnerer, EvaSchruba, AndreasSun, JiayiUtomo, DyasDOI: info:10.1051/0004-6361/201936060v. 634A121
Herrera, Cinthya N., Pety, Jérôme, Hughes, Annie, Meidt, Sharon E., Kreckel, Kathryn, Querejeta, Miguel, Saito, Toshiki, Lang, Philipp, Jiménez-Donaire, María Jesús, Pessa, Ismael, Cormier, Diane, Usero, Antonio, Sliwa, Kazimierz, Faesi, Christopher, Blanc, Guillermo A., Bigiel, Frank, Chevance, Mélanie, Dale, Daniel A., Grasha, Kathryn, Glover, Simon C. O., Hygate, Alexander P. S., Kruijssen, J. M. Diederik, Leroy, Adam K., Rosolowsky, Erik, Schinnerer, Eva et al. 2020. "The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy disk." Astronomy and Astrophysics 634:A121. https://doi.org/10.1051/0004-6361/201936060
ID: 157321
Type: article
Authors: Herrera, Cinthya N.; Pety, Jérôme; Hughes, Annie; Meidt, Sharon E.; Kreckel, Kathryn; Querejeta, Miguel; Saito, Toshiki; Lang, Philipp; Jiménez-Donaire, María Jesús; Pessa, Ismael; Cormier, Diane; Usero, Antonio; Sliwa, Kazimierz; Faesi, Christopher; Blanc, Guillermo A.; Bigiel, Frank; Chevance, Mélanie; Dale, Daniel A.; Grasha, Kathryn; Glover, Simon C. O.; Hygate, Alexander P. S.; Kruijssen, J. M. Diederik; Leroy, Adam K.; Rosolowsky, Erik; Schinnerer, Eva; Schruba, Andreas; Sun, Jiayi; Utomo, Dyas
Abstract: Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2-1) emission in the disk of nearby spiral galaxy NGC 628.
Aims: We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region.
Methods: High- resolution ALMA observations of CO(2-1) and CO(1-0) emission were used to characterize the mass and dynamical state of the "headlight" molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1-0), HCO+(1-0), and HCN(1-0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region.
Results: The unusually bright headlight cloud is massive (1 - 2 × 107 M), with a beam-diluted density of nH2 = 5 × 104 cm-3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 - 4 Myr) stellar population with mass 3 × 105 M is associated.
Conclusions: We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud.
The reduced data cubes are only available at http://https://doi.org/10. 11570/20.0001, in the page http://https://www.c anfar.net/storage/list/AstroDataCitationDOI/CISTI.CANFAR/20.0001/data
Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-forming GalaxiesSun, JiayiLeroy, Adam K.Ostriker, Eve C.Hughes, AnnieRosolowsky, ErikSchruba, AndreasSchinnerer, EvaBlanc, Guillermo A.Faesi, ChristopherKruijssen, J. M. DiederikMeidt, SharonUtomo, DyasBigiel, FrankBolatto, Alberto D.Chevance, MélanieChiang, I. -DaDale, DanielEmsellem, EricGlover, Simon C. O.Grasha, KathrynHenshaw, JonathanHerrera, Cinthya N.Jimenez-Donaire, Maria JesusLee, Janice C.Pety, JérômeQuerejeta, MiguelSaito, ToshikiSandstrom, KarinUsero, AntonioDOI: info:10.3847/1538-4357/ab781cv. 892148
Sun, Jiayi, Leroy, Adam K., Ostriker, Eve C., Hughes, Annie, Rosolowsky, Erik, Schruba, Andreas, Schinnerer, Eva, Blanc, Guillermo A., Faesi, Christopher, Kruijssen, J. M. Diederik, Meidt, Sharon, Utomo, Dyas, Bigiel, Frank, Bolatto, Alberto D., Chevance, Mélanie, Chiang, I. -Da, Dale, Daniel, Emsellem, Eric, Glover, Simon C. O., Grasha, Kathryn, Henshaw, Jonathan, Herrera, Cinthya N., Jimenez-Donaire, Maria Jesus, Lee, Janice C., Pety, Jérôme et al. 2020. "Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-forming Galaxies." The Astrophysical Journal 892:148. https://doi.org/10.3847/1538-4357/ab781c
ID: 157304
Type: article
Authors: Sun, Jiayi; Leroy, Adam K.; Ostriker, Eve C.; Hughes, Annie; Rosolowsky, Erik; Schruba, Andreas; Schinnerer, Eva; Blanc, Guillermo A.; Faesi, Christopher; Kruijssen, J. M. Diederik; Meidt, Sharon; Utomo, Dyas; Bigiel, Frank; Bolatto, Alberto D.; Chevance, Mélanie; Chiang, I. -Da; Dale, Daniel; Emsellem, Eric; Glover, Simon C. O.; Grasha, Kathryn; Henshaw, Jonathan; Herrera, Cinthya N.; Jimenez-Donaire, Maria Jesus; Lee, Janice C.; Pety, Jérôme; Querejeta, Miguel; Saito, Toshiki; Sandstrom, Karin; Usero, Antonio
Abstract: We compare the observed turbulent pressure in molecular gas, Pturb, to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, PDE. To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multiwavelength data that trace the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that Pturb correlates with - but almost always exceeds - the estimated PDE on kiloparsec scales. This indicates that the molecular gas is overpressurized relative to the large-scale environment. We show that this overpressurization can be explained by the clumpy nature of molecular gas; a revised estimate of PDE on cloud scales, which accounts for molecular gas self- gravity, external gravity, and ambient pressure, agrees well with the observed Pturb in galaxy disks. We also find that molecular gas with cloud-scale Pturb ≈ PDE ≳ 105 kB K cm-3 in our sample is more likely to be self- gravitating, whereas gas at lower pressure it appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between Pturb and the observed SFR surface density, ΣSFR, is compatible with stellar feedback-driven momentum injection in most cases, while a subset of the regions may show evidence of turbulence driven by additional sources. The correlation between ΣSFR and kpc-scale PDE in galaxy disks is consistent with the expectation from self-regulated star formation models. Finally, we confirm the empirical correlation between molecular- to-atomic gas ratio and kpc-scale PDE reported in previous works.
What is the physics behind the Larson mass-size relation?Ballesteros-Paredes, J.Román-Zúñiga, C.Salomé, Q.Zamora-Avilés, M.Jiménez-Donaire, Maria J.DOI: info:10.1093/mnras/stz2575v. 4902648–2655
Ballesteros-Paredes, J., Román-Zúñiga, C., Salomé, Q., Zamora-Avilés, M., and Jiménez-Donaire, Maria J. 2019. "What is the physics behind the Larson mass-size relation?." Monthly Notices of the Royal Astronomical Society 490:2648– 2655. https://doi.org/10.1093/mnras/stz2575
ID: 154509
Type: article
Authors: Ballesteros-Paredes, J.; Román-Zúñiga, C.; Salomé, Q.; Zamora-Avilés, M.; Jiménez-Donaire, Maria J.
Abstract: Different studies have reported a power-law mass-size relation M ∝ Rq for ensembles of molecular clouds. In the case of nearby clouds, the index of the power-law q is close to 2. However, for clouds spread all over the Galaxy, indexes larger than 2 are reported. We show that indexes larger than 2 could be the result of line-of-sight superposition of emission that does not belong to the cloud itself. We found that a random factor of gas contamination, between 0.001 per cent and 10 per cent of the line of sight, allows to reproduce the mass-size relation with q ̃ 2.2-2.3 observed in Galactic CO surveys. Furthermore, for dense cores within a single cloud, or molecular clouds within a single galaxy, we argue that, even in these cases, there is observational and theoretical evidence that some degree of superposition may be occurring. However, additional effects may be present in each case, and are briefly discussed. We also argue that defining the fractal dimension of clouds via the mass-size relation is not adequate, since the mass is not necessarily a proxy to the area, and the size reported in M-R relations is typically obtained from the square root of the area, rather than from an estimation of the size independent from the area. Finally, we argue that the statistical analysis of finding clouds satisfying the Larson's relations does not mean that each individual cloud is in virial equilibrium.
EMPIRE: The IRAM 30 m Dense Gas Survey of Nearby GalaxiesJiménez-Donaire, María J.Bigiel, F.Leroy, A. K.Usero, A.Cormier, D.Puschnig, J.Gallagher, M.Kepley, A.Bolatto, A.García-Burillo, S.Hughes, A.Kramer, C.Pety, J.Schinnerer, E.Schruba, A.Schuster, K.Walter, F.DOI: info:10.3847/1538-4357/ab2b95v. 880127
Jiménez-Donaire, María J., Bigiel, F., Leroy, A. K., Usero, A., Cormier, D., Puschnig, J., Gallagher, M., Kepley, A., Bolatto, A., García-Burillo, S., Hughes, A., Kramer, C., Pety, J., Schinnerer, E., Schruba, A., Schuster, K., and Walter, F. 2019. "EMPIRE: The IRAM 30 m Dense Gas Survey of Nearby Galaxies." The Astrophysical Journal 880:127. https://doi.org/10.3847/1538-4357/ab2b95
ID: 154274
Type: article
Authors: Jiménez-Donaire, María J.; Bigiel, F.; Leroy, A. K.; Usero, A.; Cormier, D.; Puschnig, J.; Gallagher, M.; Kepley, A.; Bolatto, A.; García-Burillo, S.; Hughes, A.; Kramer, C.; Pety, J.; Schinnerer, E.; Schruba, A.; Schuster, K.; Walter, F.
Abstract: We present EMPIRE, an IRAM 30 m large program that mapped λ = 3-4 mm dense gas tracers at ̃1-2 kpc resolution across the whole star-forming disk of nine nearby massive spiral galaxies. We describe the EMPIRE observing and reduction strategies and show new whole-galaxy maps of HCN(1-0), HCO+(1-0), HNC(1-0), and CO(1-0). We explore how the HCN-to-CO and IR-to-HCN ratios, observational proxies for the dense gas fraction and dense gas star formation efficiency, depend on host galaxy and local environment. We find that the fraction of dense gas correlates with stellar surface density, gas surface density, molecular-to-atomic gas ratio, and dynamical equilibrium pressure. In EMPIRE, the star formation rate per unit dense gas is anticorrelated with these same environmental parameters. Thus, although dense gas appears abundant in the central regions of many spiral galaxies, this gas appears relatively inefficient at forming stars. These results qualitatively agree with previous work on nearby galaxies and the Milky Way's Central Molecular Zone. To first order, EMPIRE demonstrates that the conditions in a galaxy disk set the gas density distribution and that the dense gas traced by HCN shows an environment-dependent relation to star formation. However, our results also show significant (±0.2 dex) galaxy-to-galaxy variations. We suggest that gas structure below the scale of our observations and dynamical effects likely also play an important role.
Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100 pc scales in M 51Querejeta, M.Schinnerer, E.Schruba, A.Murphy, E.Meidt, S.Usero, A.Leroy, A. K.Pety, J.Bigiel, F.Chevance, M.Faesi, C. M.Gallagher, M.García-Burillo, S.Glover, S. C. O.Hygate, A. P. S.Jiménez-Donaire, M. J.Kruijssen, J. M. D.Momjian, E.Rosolowsky, E.Utomo, D.DOI: info:10.1051/0004-6361/201834915v. 625A19
Querejeta, M., Schinnerer, E., Schruba, A., Murphy, E., Meidt, S., Usero, A., Leroy, A. K., Pety, J., Bigiel, F., Chevance, M., Faesi, C. M., Gallagher, M., García-Burillo, S., Glover, S. C. O., Hygate, A. P. S., Jiménez-Donaire, M. J., Kruijssen, J. M. D., Momjian, E., Rosolowsky, E., and Utomo, D. 2019. "Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100 pc scales in M 51." Astronomy and Astrophysics 625:A19. https://doi.org/10.1051/0004-6361/201834915
ID: 151827
Type: article
Authors: Querejeta, M.; Schinnerer, E.; Schruba, A.; Murphy, E.; Meidt, S.; Usero, A.; Leroy, A. K.; Pety, J.; Bigiel, F.; Chevance, M.; Faesi, C. M.; Gallagher, M.; García-Burillo, S.; Glover, S. C. O.; Hygate, A. P. S.; Jiménez-Donaire, M. J.; Kruijssen, J. M. D.; Momjian, E.; Rosolowsky, E.; Utomo, D.
Abstract: It remains unclear what sets the efficiency with which molecular gas transforms into stars. Here we present a new VLA map of the spiral galaxy M 51 in 33 GHz radio continuum, an extinction-free tracer of star formation, at 3″ scales (˜100 pc). We combined this map with interferometric PdBI/NOEMA observations of CO(1-0) and HCN(1-0) at matched resolution for three regions in M 51 (central molecular ring, northern and southern spiral arm segments). While our measurements roughly fall on the well-known correlation between total infrared and HCN luminosity, bridging the gap between Galactic and extragalactic observations, we find systematic offsets from that relation for different dynamical environments probed in M 51; for example, the southern arm segment is more quiescent due to low star formation efficiency (SFE) of the dense gas, despite its high dense gas fraction. Combining our results with measurements from the literature at 100 pc scales, we find that the SFE of the dense gas and the dense gas fraction anti-correlate and correlate, respectively, with the local stellar mass surface density. This is consistent with previous kpc-scale studies. In addition, we find a significant anti-correlation between the SFE and velocity dispersion of the dense gas. Finally, we confirm that a correlation also holds between star formation rate surface density and the dense gas fraction, but it is not stronger than the correlation with dense gas surface density. Our results are hard to reconcile with models relying on a universal gas density threshold for star formation and suggest that turbulence and galactic dynamics play a major role in setting how efficiently dense gas converts into stars. The VLA map, Table A.1, and full Table A.2 are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A19
Submillimeter Array Observations of Extended CO (J = 2 ‑ 1) Emission in the Interacting Galaxy NGC 3627Law, Charles J.Zhang, QizhouRicci, LucaPetitpas, GlenJiménez-Donaire, Maria J.Ueda, JunkoLu, XingDunham, Michael M.DOI: info:10.3847/1538-4357/aadca9v. 86517
Law, Charles J., Zhang, Qizhou, Ricci, Luca, Petitpas, Glen, Jiménez-Donaire, Maria J., Ueda, Junko, Lu, Xing, and Dunham, Michael M. 2018. "Submillimeter Array Observations of Extended CO (J = 2 ‑ 1) Emission in the Interacting Galaxy NGC 3627." The Astrophysical Journal 865:17. https://doi.org/10.3847/1538-4357/aadca9
ID: 149162
Type: article
Authors: Law, Charles J.; Zhang, Qizhou; Ricci, Luca; Petitpas, Glen; Jiménez-Donaire, Maria J.; Ueda, Junko; Lu, Xing; Dunham, Michael M.
Abstract: We present moderate (∼5″) and high angular resolution (∼1″) observations of 12CO (J = 2 ‑ 1) emission toward the nearby interacting galaxy NGC 3627 taken with the Submillimeter Array (SMA). These SMA mosaic maps of NGC 3627 reveal a prominent nuclear peak, inter-arm regions, and diffuse, extended emission in the spiral arms. A velocity gradient of ∼400–450 km s‑1 is seen across the entire galaxy with velocity dispersions ranging from ≲80 km s‑1 toward the nuclear region to ≲15 km s‑1 in the spiral arms. We also detect unresolved 13CO (J = 2 ‑ 1) line emission toward the nuclear region, southern bar end, and in a relatively isolated clump in the southern portion of the galaxy, while no C18O(J = 2 ‑ 1) line emission is detected at a 3σ rms noise level of 42 mJy beam‑1 per 20 km s‑1 channel. Using RADEX modeling with a large velocity gradient approximation, we derive kinetic temperatures ranging from ∼5 to 10 K (in the spiral arms) to ∼25 K (at the center) and H2 number densities from ∼400 to 1000 cm‑3 (in the spiral arms) to ∼12,500 cm‑3 (at the center). From this density modeling, we find a total H2 mass of 9.6 × 109 M , which is ∼50% higher than previous estimates made using a constant H2–CO conversion factor, but is largely dependent on the assumed vertical distribution of the CO gas. With the exception of the nuclear region, we also identify a tentative correlation between star formation efficiency and kinetic temperature. We derive a galactic rotation curve, finding a peak velocity of ∼207 km s‑1 and estimate a total dynamical mass of 4.94 ± 0.70 × 1010 M at a galactocentric radius of ∼6.2 kpc (121″).