ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH<sup>+</sup>ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs

Dahlstrom, Julie; York, Donald G.; Welty, D. E.; Oka, Takeshi; Hobbs, L. M.; Johnson, Sean D.; Friedman, S. D.; Jiang, Zihao; Rachford, B. L.; Sherman, R. D.; Snow, Theodore P.; Sonnentrucker, Paule

doi:10.1088/0004-637x/773/1/41

Cited by 42 publications

(44 citation statements)

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“…This discrepancy may reflect an underestimate of R V , which is seen to be higher than the average Galactic value of 3.1 in lines of sight towards star-forming regions (see e.g. Cardelli et al 1989;Hoffmeister et al 2008;Dahlstrom et al 2013). Alternatively, the DIB carrier(s) may be less abundant in star forming regions, which would provide a constraint on its nature.…”

Section: Extinction and Nebular Spectrummentioning

confidence: 95%

RCW36: characterizing the outcome of massive star formation

Ellerbroek

Bik

Kaper

et al. 2013

A&A

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Context. Massive stars play a dominant role in the process of clustered star formation, with their feedback into the molecular cloud through ionizing radiation, stellar winds, and outflows. The formation process of massive stars is poorly constrained because of their scarcity, the short formation timescale, and obscuration. By obtaining a census of the newly formed stellar population, the star formation history of the young cluster and the role of the massive stars within it can be unraveled. Aims. We aim to reconstruct the formation history of the young stellar population of the massive star-forming region RCW 36. We study several dozen individual objects, both photometrically and spectroscopically, looking for signs of multiple generations of young stars and investigating the role of the massive stars in this process. Methods. We obtain a census of the physical parameters and evolutionary status of the young stellar population. Using a combination of near-infrared photometry and spectroscopy we estimate the ages and masses of individual objects. We identify the population of embedded young stellar objects (YSOs) by their infrared colors and emission line spectra. Results. RCW 36 harbors a stellar population of massive and intermediate-mass stars located around the center of the cluster. Class 0/I and II sources are found throughout the cluster. The central population has a median age of 1.1 ± 0.6 Myr. Of the stars that could be classified, the most massive ones are situated in the center of the cluster. The central cluster is surrounded by filamentary cloud structures; within these, some embedded and accreting YSOs are found. Conclusions. Our age determination is consistent with the filamentary structures having been shaped by the ionizing radiation and stellar winds of the central massive stars. The formation of a new generation of stars is ongoing, as demonstrated by the presence of embedded protostellar clumps and two exposed protostellar jets.

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Section: Extinction and Nebular Spectrummentioning

confidence: 95%

RCW36: characterizing the outcome of massive star formation

Ellerbroek

Bik

Kaper

et al. 2013

A&A

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“…These DIBs and other interstellar lines were confirmed in spectra of higher resolving power by examination of spectra from the AAT, in archival FEROS spectra and in new spectra obtained by us with MIKE in 2012. While we focus here on the extended red wings, other details of the profiles are considered by Dahlstrom et al (2013). Seven other DIBs in Herschel 36 showed ETR while 22 cases showed no significant ETR and 11 cases were ambiguous for want of high enough S/N.…”

Section: Dibs and Molecular Lines In The Spectrum Of Herschel 36mentioning

confidence: 99%

“…Small differences in the profiles of optical DIBs from line-of-sight to line-of-sight have been noted by many authors, but only on scales of <10 km s −1 except where widely spaced interstellar components are involved. A detailed summary is given by Dahlstrom et al (2013). Shifts and profile changes were once thought to be indicative of possible grain surface origins of DIB carriers, but recent polarization measurements of DIBs by Cox et al (2011) seem to rule that out.…”

Section: Introductionmentioning

confidence: 99%

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Anomalously Broad Diffuse Interstellar Bands and Excited CH⁺ Absorption in the Spectrum of Herschel 36

et al. 2013

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Abstract. Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6Å are found in absorption along the line of sight to Herschel 36, an O star system next to the bright Hourglass nebula of the Hii region Messier 8. Excited lines of CH and CH + are seen as well. We show that the region is very compact and itemize other anomalies of the gas. An infrared-bright star within 400 AU is noted. The combination of these effects produces anomalous DIBs, interpreted by Oka et al. (2013, see also this volume) as being caused predominantly by infrared pumping of rotational levels of relatively small molecules.

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“…However, DIBs seem sensitive to the radiation field of these stars (Vos et al 2011;Dahlstrom et al 2013;Cordiner et al 2013), and therefore hot stars are not the optimal targets to prove the typical conditions of the general ISM of our Galaxy. In fact, Raimond et al (2012) showed how using cooler target stars correlations between DIBs (and reddening) improve, confirming that the radiation field of UV bright stars has a significant influence on the DIB strength.…”

Section: Introductionmentioning

confidence: 99%

Measuring diffuse interstellar bands with cool stars

Monreal-Ibero

Lallement

2017

A&A

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Context. Diffuse Stellar Bands (DIBs) are ubiquitous in stellar spectra. Traditionally, they have been studied through their extraction from hot (early-type) stars, because of their smooth continuum. In an era where there are several going-on or planned massive Galactic surveys using multi-object spectrographs, cool (late-type) stars constitute an appealing set of targets. However, from the technical point of view, the extraction of DIBs in their spectra is more challenging due to the complexity of the continuum. Aims. In this contribution we will provide the community with an improved set of stellar lines in the spectral regions associated to the strong DIBs at λ6196.0, λ6269.8, λ6283.8, and λ6379.3. These lines will allow for the creation of better stellar synthetic spectra, reproducing the background emission and a more accurate extraction of the magnitudes associated with a given DIB (e.g. equivalent width, radial velocity). Methods. The Sun and Arcturus were used as representative examples of dwarf and giant stars, respectively. A high quality spectrum for each of them was modeled using TURBOSPECTRUM and the VALD stellar line list. The oscillator strength log(g f ) and/or wavelength of specific lines were modified to create synthetic spectra where the residuals in both the Sun and Arcturus were minimized. Results. The TURBOSPECTRUM synthetic spectra based on the improved line lists reproduce the observed spectra for the Sun and Arcturus in the mentioned spectral ranges with greater accuracy. Residuals between the synthetic and observed spectra are always ∼ < 10%, much better than with previously existing options. The new line list has been tested with some characteristic spectra, from a variety of stars, including both giant and dwarf stars, and under different degrees of extinction. As it happened with the Sun and Arcturus residuals in the fits used to extract the DIB information are smaller when using synthetic spectra made with the updated line lists. Tables with the updated parameters are provided to the community.

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ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH⁺ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs

Cited by 42 publications

References 103 publications

RCW36: characterizing the outcome of massive star formation

RCW36: characterizing the outcome of massive star formation

Anomalously Broad Diffuse Interstellar Bands and Excited CH⁺ Absorption in the Spectrum of Herschel 36

Measuring diffuse interstellar bands with cool stars

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ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH+ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs

Cited by 42 publications

References 103 publications

RCW36: characterizing the outcome of massive star formation

RCW36: characterizing the outcome of massive star formation

Anomalously Broad Diffuse Interstellar Bands and Excited CH+ Absorption in the Spectrum of Herschel 36

Measuring diffuse interstellar bands with cool stars

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About

ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH⁺ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs

Anomalously Broad Diffuse Interstellar Bands and Excited CH⁺ Absorption in the Spectrum of Herschel 36