The interstellar medium in the starburst regions of NGC 253 and NGC 3256

Carral, P.; Hollenbach, D. J.; Lord, S. D.; Colgan, Sean W. J.; Haas, Michael R.; Rubin, R. H.; Erickson, E. F.

doi:10.1086/173801

Cited by 95 publications

(131 citation statements)

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“…Modelling of Hii and PDR regions of starburst galaxies NGC 253 and M82 (Carral et al 1994;Lord et al 1996;Colbert et al 1999) has also shown that PDRs account for ∼70% of the [Cii] emission, with similar results (70 -85%) reported by Kramer et al (2005) in their study of M51 and M83. Based on this evidence, numerous studies of higher redshift (z ∼ 1-6) IRbright galaxies thus adopt a 0.7 correction factor to account for the ionised gas contribution to the Spatially-resolved studies with the Herschel Very Nearby Galaxies Survey have also demonstrated the varying distributions of neutral and ionised gas within local galaxies using the method of Oberst et al (2006Oberst et al ( , 2011 with both direct (e.g.…”

Section: Adjustments To Observed Quantitiessupporting

confidence: 71%

Vales

Hughes

Ibar

Villanueva

et al. 2017

A&A

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We use new Band-3 CO(1-0) observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the physical conditions in the interstellar gas of a sample of 27 dusty main-sequence star-forming galaxies at 0.03 < z < 0.2 present in the Valparaíso ALMA Line Emission Survey (VALES). The sample is drawn from far-IR bright galaxies over ∼160 deg 2 in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), which is covered by high-quality ancillary data including Herschel [Cii] 158 µm spectroscopy and far-infrared (FIR) photometry. The [Cii] and CO(1-0) lines are both detected at > 5σ in 26 sources. We find an average [Cii] to CO(1-0) luminosity ratio of 3500 ± 1200 for our sample that is consistent with previous studies. Using the [Cii], CO(1-0) and FIR measurements as diagnostics of the physical conditions of the interstellar medium, we compare these observations to the predictions of a photodissociation region (PDR) model to determine the gas density, surface temperature, pressure, and the strength of the incident far-ultraviolet (FUV) radiation field, G 0 , normalised to the Habing Field. The majority of our sample exhibit hydrogen densities of 4 < log n/cm 3 < 5.5 and experience an incident FUV radiation field with strengths of 2 < log G 0 < 3 when adopting standard adjustments. A comparison to galaxy samples at different redshifts indicates that the average strength of the FUV radiation field appears constant up to redshift z ∼ 6.4, yet the neutral gas density increases as a function of redshift by a factor of ∼100 from z = 0 to z = 0.2 that persists regardless of various adjustments to our observable quantities. Whilst this evolution could provide an explanation for the observed evolution of the star formation rate density with cosmic time, the result most likely arises from a combination of observational biases when using different suites of emission lines as diagnostic tracers of PDR gas.

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Section: Adjustments To Observed Quantitiessupporting

confidence: 71%

Vales

Hughes

Ibar

Villanueva

et al. 2017

A&A

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“…For sources where the environment of massive star formation resembles exposed PDRs (such as M 82 and NGC 253; Carral et al 1994;Lord et al 1996), the three methods discussed above will give reasonable results. On the other hand, for sources which resemble embedded star formation (e.g.…”

Section: Conversion From Pah Luminosity To Ir Luminositymentioning

confidence: 92%

Polycyclic Aromatic Hydrocarbons as a Tracer of Star Formation?

Peeters

Spoon

Tielens

2004

ApJ

393

487

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Infrared (IR) emission features at 3. 3, 6.2, 7.7, 8.6 and 11.3 µm are generally attributed to IR fluorescence from (mainly) FUV pumped large Polycyclic Aromatic Hydrocarbon (PAH) molecules. As such, these features trace the FUV stellar flux and are thus a measure of star formation. We examined the IR spectral characteristics of Galactic massive star forming regions and of normal and starburst galaxies, as well as AGNs and ULIRGs. The goal of this study is to analyze if PAH features are a good qualitative and/or quantitative tracer of star formation and hence the application of PAH emission as a diagnostic tool in order to identify the dominant processes contributing to the infrared emission from Seyfert's and ULIRGs. We develop a new MIR/FIR diagnostic diagram based upon our Galactic sample and compare it to the diagnostic tools of Genzel et al. (1998) and(Laurent et al. 2000), with these diagnostic tools also applied to our Galactic sample. This MIR/FIR diagnostic is derived from the FIR normalized 6.2 µm PAH flux and the FIR normalized 6.2 µm continuum flux. Within this diagram, the Galactic sources form a sequence spanning a range of 3 orders of magnitude in these ratios, ranging from embedded compact H II regions to exposed Photo Dissociation Regions (PDRs) and the (diffuse) ISM. However, the variation in the 6.2 µm PAH feature-to-continuum ratio is relative small. Comparison -2 -of our extragalactic sample with our Galactic sources revealed an excellent resemblance of normal and starburst galaxies to exposed PDRs. While Seyfert-2's coincide with the starburst trend, Seyfert-1's are displaced by at least a factor 10 in 6.2 µm continuum flux, in accordance with general orientation dependent unification schemes for AGNs. ULIRGs show a diverse spectral appearance. Some show a typical AGN hot dust continuum. More, however, are either starburstlike or show signs of strong dust obscuration in the nucleus. One characteristic of the ULIRGs also seems to be the presence of more prominent FIR emission than either starburst galaxies or AGNs. We discuss the observed variation in the Galactic sample in view of the evolutionary state and the PAH/dust abundance and discuss the use of PAHs as quantitative tracers of star formation activity. Based on these investigations we find that PAHs may be better suited as a tracer of B stars, which dominate the Galactic stellar energy budget, than as a tracer of massive star formation (O stars).

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“…We test the physicality of our PDR models with greater precision by comparing the atomic gas to the molecular gas. Carral et al (1994) uses [CII] 158 μm to trace the atomic gas mass in the inner 40 of NGC 253 and finds an atomic mass of 2.4×10 6 M . This atomic mass is 30 times smaller than the molecular gas that we observe in our 32.5 beam, which is similar to the findings of Bradford et al (2003) and Hailey-Dunsheath et al (2008).…”

Section: Pdr Analysismentioning

confidence: 99%

Radiative and mechanical feedback into the molecular gas of NGC 253

Rosenberg

Kazandjian

Werf

et al. 2014

A&A

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Starburst galaxies are galaxies or regions of galaxies undergoing intense periods of star formation. Understanding the heating and cooling mechanisms in these galaxies can give us insight to the driving mechanisms that fuel the starburst. Molecular emission lines play a crucial role in the cooling of the excited gas. With Herschel Spectral and Photometric Imaging Receiver we have been able to observe the rich molecular spectrum towards the central region of NGC 253. Carbon monoxide (CO, J = 4−3 to 13−12) is the brightest molecule in the Herschel wavelength range and together with ground-based low-J observations, the line fluxes trace the excitation of CO. By studying the CO excitation ladder and comparing the intensities to models, we investigate whether the gas is excited by UV radiation, X-rays, cosmic rays, or turbulent heating. Comparing the 12 CO and 13 CO observations to large velocity gradient models and photon-dominated region (PDR) models we find three main interstellar medium (ISM) phases. We estimate the density, temperature, and masses of these ISM phases. By adding 13 CO, HCN, and HNC line intensities, we are able to constrain these degeneracies and determine the heating sources. The first ISM phase responsible for the low-J CO lines is excited by PDRs, but the second and third phases, responsible for the mid to high-J CO transitions, require an additional heating source. We find three possible combinations of models that can reproduce our observed molecular emission. Although we cannot determine which of these is preferable, we can conclude that mechanical heating is necessary to reproduce the observed molecular emission and cosmic ray heating is a negligible heating source. We then estimate the mass of each ISM phase; 6 × 10 7 M for phase 1 (low-J CO lines), 3 × 10 7 M for phase 2 (mid-J CO lines), and 9 × 10 6 M for phase 3 (high-J CO lines) for a total system mass of 1 × 10 8 M .

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The interstellar medium in the starburst regions of NGC 253 and NGC 3256

Cited by 95 publications

References 0 publications

Vales

Vales

Polycyclic Aromatic Hydrocarbons as a Tracer of Star Formation?

Radiative and mechanical feedback into the molecular gas of NGC 253

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