Radiative and mechanical feedback into the molecular gas of NGC 253

Rosenberg, M. J. F.; Kazandjian, M. V.; Werf, P. P. van der; Israel, F. P.; Meijerink, R.; Weiß, A.; Requeña-Torres, M. A.; Güsten, R.

doi:10.1051/0004-6361/201323109

Cited by 57 publications

(96 citation statements)

References 38 publications

(68 reference statements)

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“…The densities and temperatures found for the cold component of CO are comparable with those found in starburst galaxies like, e.g., NGC 253 (Rosenberg et al 2014, their Tables 2-4), but the warm component requires excitation conditions with at least one order of magnitude higher density and column density. Similar discrepancies are found when comparing with the excitation conditions estimated for Seyfert galaxies like NGC 1068 (Spinoglio et al 2012, their Table 3).…”

Section: Excitation Of the Average Emission In M17 Swsupporting

confidence: 71%

“…We analyze the underlying excitation conditions from the LSED of some of the clumps fitted to their spectral lines. We are particularly interested in these molecules because their distribution and excitation is responsive to energetic radiative environments, which has led to their extensive usage for, e.g., disentangling star formation vs. black hole accretion and shocks, in the nuclear region of active galaxies (e.g., Sternberg et al 1994;Kohno et al 1999Kohno et al , 2001Kohno 2003Kohno , 2005Usero et al 2004;Pérez-Beaupuits et al 2007, 2009García-Burillo et al 2008Loenen et al 2008;Krips et al 2008;Rosenberg et al 2014;Viti et al 2014) Given the relative youth ( 1 Myr; e.g., Lada et al 1991;Hanson et al 1997) of the main ionizing cluster (NGC 6618) of M17 SW, and the absence of evolved stars, it is likely that supernovae have not yet occurred. This makes M17 SW an ideal place to study the radiative interactions of massive stars with their surrounding gas/dust and stellar disks, without the influence of nearby supernovae.…”

Section: Introductionmentioning

confidence: 99%

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Disentangling the excitation conditions of the dense gas in M17 SW

Pérez-Beaupuits

Güsten

Spaans

et al. 2015

A&A

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Context. Stars are formed in dense molecular clouds. These dense clouds experience radiative feedback from UV photons, and X-ray from stars, embedded prestellar cores, young stellar objects (YSOs), and ultra compact H II regions. This radiative feedback affects the chemistry and thermodynamics of the gas. Aims. We aim to probe the chemical and energetic conditions created by radiative feedback through observations of multiple CO, HCN, and HCO + transitions. We measure the spatial distribution and excitation of the dense gas (n(H 2 ) > 10 4 cm −3 ) in the core region of M17 SW and aim to investigate the influence of UV radiation fields. Methods. We used the dual band receiver GREAT on board the SOFIA airborne telescope to obtain a 5. 7 × 3. 7 map of the J = 16 → 15, J = 12 → 11, and J = 11 → 10 transitions of 12 CO in M17 SW. We compare these maps with corresponding APEX and IRAM 30 m telescope data for low-and mid-J CO, HCN, and HCO + emission lines, including maps of the HCN J = 8 → 7 and HCO + J = 9 → 8 transitions. The excitation conditions of 12 CO, HCO + , and HCN are estimated with a two-phase non-LTE radiative transfer model of the line spectral energy distributions (LSEDs) at four selected positions. The energy balance at these positions is also studied. Results. We obtained extensive LSEDs for the CO, HCN, and HCO + molecules toward M17 SW. These LSEDs can be fit simultaneously using the same density and temperature in the two-phase models and to the spectra of all three molecules over a ∼12 square arc minute size region of M17 SW. Temperatures of up to 240 K are found toward the position of the peak emission of the 12 CO J = 16 → 15 line. High densities of 10 6 cm −3 were found at the position of the peak HCN J = 8 → 7 emission. Conclusions. We found HCO + /HCN line ratios larger than unity, which can be explained by a lower excitation temperature of the higher-J HCN lines. The LSED shape, particularly the high-J tail of the CO lines observed with SOFIA/GREAT, is distinctive for the underlying excitation conditions. The cloudlets associated with the cold component of the models are magnetically subcritical and supervirial at most of the selected positions. The warm cloudlets instead are all supercritical and also supervirial. The critical magnetic field criterion implies that the cold cloudlets at two positions are partially controlled by processes that create and dissipate internal motions. Supersonic but sub-Alfvénic velocities in the cold component at most selected positions indicate that internal motions are likely magnetohydrodynamic (MHD) waves. Magnetic pressure dominates thermal pressure in both gas components at all selected positions, assuming random orientation of the magnetic field. The magnetic pressure of a constant magnetic field throughout all the gas phases can support the total internal pressure of the cold components, but cannot support the internal pressure of the warm components. If the magnetic field scales as B ∝ n 2/3 , then the evolution of the cold cloudlets at two sel...

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Section: Excitation Of the Average Emission In M17 Swsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Disentangling the excitation conditions of the dense gas in M17 SW

Pérez-Beaupuits

Güsten

Spaans

et al. 2015

A&A

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“…This is demonstrated fitting a pure PDR model to the high-J CO lines, and is clear in the degeneracy parameter space diagrams shown in Fig. 3 by Rosenberg et al (2014).…”

Section: Limitations and Usefulness Of The 12 Co Laddermentioning

confidence: 60%

“…The parameters of the fits are given in Table 4. We have estimated the masses of each ISM phase using the equation from Rosenberg et al (2014):…”

Section: Full Pdr Analysismentioning

confidence: 99%

Molecular gas heating in Arp 299

Rosenberg

Meijerink

Israel

et al. 2014

A&A

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ABSTRACT(Ultra) luminous infrared galaxies ((U)LIRGs) are nearby laboratories that allow us to study similar processes to those occurring in high redshift submillimeter galaxies. Understanding the heating and cooling mechanisms in these galaxies can give us insight into the driving mechanisms in their more distant counterparts. Molecular emission lines play a crucial role in cooling excited gas, and recently, with Herschel Space Observatory we have been able to observe the rich molecular spectrum. Carbon monoxide (CO) is the most abundant and one of the brightest molecules in the Herschel wavelength range. CO transitions from J = 4-3 to 13-12 are observed with Herschel, and together, these lines trace the excitation of CO. We study Arp 299, a colliding galaxy group, with one component (A) harboring an active galatic nucleus and two more (B and C) undergoing intense star formation. For Arp 299 A, we present PACS spectrometer observations of high-J CO lines up to J = 20-19 and JCMT observations of 13 CO and HCN to discern between UV heating and alternative heating mechanisms. There is an immediately noticeable difference in the spectra of Arp 299 A and Arp 299 B+C, with source A having brighter high-J CO transitions. This is reflected in their respective spectral energy line distributions. We find that photon-dominated regions (PDRs, UV heating) are unlikely to heat all the gas since a very extreme PDR is necessary to fit the high-J CO lines. In addition, this extreme PDR does not fit the HCN observations, and the dust spectral energy distribution shows that there is not enough hot dust to match the amount expected from such an extreme PDR. Therefore, we determine that the high-J CO and HCN transitions are heated by an additional mechanism, namely cosmic ray heating, mechanical heating, or X-ray heating. We find that mechanical heating, in combination with UV heating, is the only mechanism that fits all molecular transitions. We also constrain the molecular gas mass of Arp 299 A to 3 × 10 9 M and find that we need 4% of the total heating to be mechanical heating, with the rest UV heating. Finally, we caution against the use of 12 CO alone as a probe of physical properties in the interstellar medium.

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“…(4) manifests a direct connection between and L IR or if both CO and L IR are driven in similar ways by some other parameter, in which case their spatial distribution inside galaxies might differ. Evidence from local galaxies suggests that CO emission with T kin > 50 K, as favored by our LVG modeling, might not be excited by the photodissociation region, but more likely by mechanical heating from shocks (e.g., Rosenberg et al 2014;Meijerink et al 2013), which most likely are driven by winds connected to the SF regions. Future comparisons of high spatial resolution maps of CO with HCN, for example, are required to clarify whether this is a viable approach or not, that is, to clarify if CO can be used as a high-fidelity tracer of the star-forming gas.…”

Section: A Linear Correlation Between L Co[5-4] and L Ir ?mentioning

confidence: 69%

CO excitation of normal star-forming galaxies out toz= 1.5 as regulated by the properties of their interstellar medium

Daddi

Dannerbauer

Liu

et al. 2015

A&A

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We investigate the CO excitation of normal (near-IR selected BzK) star-forming (SF) disk galaxies at z = 1.5 using IRAM Plateau de Bure observations of the CO[2-1], CO , and CO[5-4] transitions for four galaxies, including VLA observations of CO[1-0] for three of them, with the aim of constraining the average state of H 2 gas. By exploiting previous knowledge of the velocity range, spatial extent, and size of the CO emission, we measure reliable line fluxes with a signal-to-noise ratio >4-7 for individual transitions. While the average CO spectral line energy distribution (SLED) has a subthermal excitation similar to the Milky Way (MW) up to CO[3-2], we show that the average CO emission is four times stronger than assuming MW excitation. This demonstrates that there is an additional component of more excited, denser, and possibly warmer molecular gas. The ratio of CO[5-4] to lower-J CO emission is lower than in local (ultra-)luminous infrared galaxies (ULIRGs) and high-redshift starbursting submillimeter galaxies, however, and appears to be closely correlated with the average intensity of the radiation field U and with the star formation surface density, but not with the star formation efficiency. The luminosity of the CO transition is found to be linearly correlated with the bolometric infrared luminosity over four orders of magnitudes. For this transition, z = 1.5 BzK galaxies follow the same linear trend as local spirals and (U)LIRGs and high-redshift star-bursting submillimeter galaxies. The CO[5-4] luminosity is thus empirically related to the dense gas and might be a more convenient way to probe it than standard high-density tracers that are much fainter than CO. We see excitation variations among our sample galaxies that can be linked to their evolutionary state and clumpiness in optical rest-frame images. In one galaxy we see spatially resolved excitation variations, where the more highly excited part of the galaxy corresponds to the location of massive SF clumps. This provides support to models that suggest that giant clumps are the main source of the high-excitation CO emission in high-redshift disk-like galaxies.

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Radiative and mechanical feedback into the molecular gas of NGC 253

Cited by 57 publications

References 38 publications

Disentangling the excitation conditions of the dense gas in M17 SW

Disentangling the excitation conditions of the dense gas in M17 SW

Molecular gas heating in Arp 299

CO excitation of normal star-forming galaxies out toz= 1.5 as regulated by the properties of their interstellar medium

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