Infrared cirrus - New components of the extended infrared emission

Low, F. J.; Beintema, D. A.; Gautier, T. N.; Gillett, F. C.; Beichman, C. A.; Neugebauer, G.; Young, ET; Aumann, H. H.; Boggess, N. W.; Emerson, J. P.; Habing, H. J.; Hauser, M. G.; Houck, [No Value]; Rowan-Robinson, M.; Soifer, B. T.; Walker, R. G.; Wesselius, P. R.

doi:10.1086/184213

Cited by 426 publications

(220 citation statements)

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“…The diffuse Galactic cirrus emission, identified early with IRAS (Low et al 1984), is thought to be due to the ISM, which is constantly being injected with energy through spiral shocks and stellar feedback. The emission we see as cirrus most likely comes from a large column of diffuse dust, rather than a single cloud.…”

Section: Properties Of the Cirrus Cloud Emissionmentioning

confidence: 99%

Characterizing precursors to stellar clusters withHerschel

Battersby

Bally

Ginsburg

et al. 2011

A&A

158

218

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Context. Despite their profound effect on the universe, the formation of massive stars and stellar clusters remains elusive. Recent advances in observing facilities and computing power have brought us closer to understanding this formation process. In the past decade, compelling evidence has emerged that suggests infrared dark clouds (IRDCs) may be precursors to stellar clusters. However, the usual method for identifying IRDCs is biased by the requirement that they are seen in absorption against background mid-IR emission, whereas dust continuum observations allow cold, dense pre-stellar-clusters to be identified anywhere. Aims. We aim to understand what dust temperatures and column densities characterize and distinguish IRDCs, to explore the population of dust continuum sources that are not IRDCs, and to roughly characterize the level of star formation activity in these dust continuum sources. Methods. We use Hi-GAL 70 to 500 μm data to identify dust continuum sources in the = 30 • and = 59 • Hi-GAL science demonstration phase (SDP) fields, to characterize and subtract the Galactic cirrus emission, and perform pixel-by-pixel modified blackbody fits on cirrus-subtracted Hi-GAL sources. We utilize archival Spitzer data to indicate the level of star-forming activity in each pixel, from mid-IR-dark to mid-IR-bright. Results. We present temperature and column density maps in the Hi-GAL = 30 • and = 59 • SDP fields, as well as a robust algorithm for cirrus subtraction and source identification using Hi-GAL data. We report on the fraction of Hi-GAL source pixels which are mid-IR-dark, mid-IR-neutral, or mid-IR-bright in both fields. We find significant trends in column density and temperature between mid-IR-dark and mid-IR-bright pixels; mid-IR-dark pixels are about 10 K colder and have a factor of 2 higher column density on average than mid-IR-bright pixels. We find that Hi-GAL dust continuum sources span a range of evolutionary states from preto star-forming, and that warmer sources are associated with more star formation tracers. Additionally, there is a trend of increasing temperature with tracer type from mid-IR-dark at the coldest, to outflow/maser sources in the middle, and finally to 8 and 24 μm bright sources at the warmest. Finally, we identify five candidate IRDC-like sources on the far-side of the Galaxy. These are cold (∼20 K), high column density (N(H 2 ) > 10 22 cm −2 ) clouds identified with Hi-GAL which, despite bright surrounding mid-IR emission, show little to no absorption at 8 μm. These are the first inner Galaxy far-side candidate IRDCs of which the authors are aware.

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Section: Properties Of the Cirrus Cloud Emissionmentioning

confidence: 99%

Characterizing precursors to stellar clusters withHerschel

Battersby

Bally

Ginsburg

et al. 2011

A&A

158

218

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“…These were heavily used for almost 20 years with almost 2,000 citations until the easy access of IR data from the Infrared Astronomy Satellite (IRAS). IRAS observed diffuse emission from interstellar dust over the entire sky (Low et al 1984) in 4 bands (12, 25, 60, and 100 μm), where the emission in the longer wavelength bands was due to thermal emission from large grains at a temperature of about 20 K and that at 12 and 25 μm was due to stochastic emission from small grains or large 216 J. Murthy molecules; and the 60 μm emission is from a mix of both small and large grain emission. The extinction throughout the Galaxy was calculated by Schlegel, Finkbeiner, & Davis (1998) from the 100 μm emission modified by the temperature of the grains.…”

Section: Techniquesmentioning

confidence: 99%

The 3-Dimensional Distribution of Interstellar Dust

Murthy

2013

Proc. IAU

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Abstract. A knowledge of the three dimensional distribution of interstellar dust is critical in interpreting all observations of the sky, particularly in the understanding of the structure and morphology of our Galaxy. It has been much easier to map the integrated dust extinction through the Galaxy, which is needed in modeling extragalactic sources, but this yields an overestimate of reddening to Galactic objects. Massive surveys, such as Gaia, present both a problem in that the distribution of interstellar dust must be known in order to model the internal structure of the Galaxy and an opportunity in that multi-color data may be used to deconvolve the dust distribution. I will present the current state of the modeling, which is yet in its early stages.

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“…In particular, at about the same time Kris Sellgren performed her breakthrough study, the IRAS mission discovered widespread emission at 12 and 25 µm in the diffuse interstellar medium of the Milky Way and other galaxies (Low et al 1984). While there was no spectrum, it was quickly surmised that this emission was, in essence, the UIR bands at 7.7, 8.6, and 11.3 µm in combination with a continuum steeply rising towards longer wavelengths and all pumped by the interstellar radiation field (Puget et al 1985).…”

Section: The Pah Hypothesismentioning

confidence: 99%

25 years of PAH hypothesis

Tielens

2011

EAS Publications Series

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Abstract. Strong IR emission features at 3. 3, 6.2, 7.7, 8.6, and 11.2 µm are a common characteristic of the interstellar medium of the Milky Way and nearby galaxies and out to redshifts of 3. Here, we review the history of the PAH hypothesis which attributes these emission features to vibrational fluorescence of large (∼ 50 carbon-atom Polycyclic Aromatic Hydrocarbon molecules pumped by ultraviolet photons from nearby stars or the average interstellar radiation field. Over the last 25 years, our insight in the characteristics of these molecules and their role in the Universe has greatly improved and the PAH hypothesis is alive and well; not in the least due a remarkable adaptability. Not surprisingly, the precise characteristics of these species remains to be defined. The early yearsOver the last three decades our understanding of the interstellar medium has increased dramatically. To a large extent this has been driven by rapid developments in infrared detector technology driven by the Cold War. Sensitive infrared spectrometers operating in all the infrared windows are now standard on all major ground-based infrared observatories and major infrared space missions have probed the Universe at all infrared wavelengths. As soon as the infrared sky opened up for spectroscopy in the early 70ies, Gillett et al. (1973) discovered broad emission features in the L (3 µm) and N (10 µm) band windows (Fig. 1). While a good fit could be obtained to the profile and peak position of the 11.3 µm band with carbonates, air-borne observatories refuted this identification since the strong band at 6.85 µm was not detected (Russell et al. 1977;Willner et al. 1979). Instead, these observations revealed that the the 3.3 and 11.3 µm bands were part of a set of strong bands -together with bands at 6.2, 7.7, and 8.6 µm -that occured together. These and subsequent observations established that these broad IR emission features were a common characteristic of all objects where strong ultraviolet (UV) photons illuminated nearby material. Surprisingly, the nature of

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Infrared cirrus - New components of the extended infrared emission

Cited by 426 publications

References 0 publications

Characterizing precursors to stellar clusters withHerschel

Characterizing precursors to stellar clusters withHerschel

The 3-Dimensional Distribution of Interstellar Dust

25 years of PAH hypothesis

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