The Excitation of Extended Red Emission: New Constraints on Its Carrier from<i>Hubble Space Telescope</i>Observations of NGC 7023

Witt, A. N.; Gordon, K. D.; Vijh, U.; Sell, Paul H.; Smith, T. Lynn; Xie, Rui-Hua

doi:10.1086/498052

Cited by 94 publications

(141 citation statements)

References 58 publications

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“…The overall distribution of the thermal infrared emission in VdB 139 appears similar to RS Pup, with irregular filamentary structures and knots. These structures, that are also observable in the visible images of the nebula in scattered light (Witt et al 2006), are typical of the turbulent ISM in star forming regions (Boulanger 2007;Dwarkadas 2008).…”

Section: Origins and Evolution Of The Csesmentioning

confidence: 78%

“…Considering their masses, the two stars will cross the instability strip in the HR diagram and become Cepheids within a few tens of million years. The bright pair illuminates a large circumstellar nebula that was extensively studied at visible (Witt et al 2006;Berné et al 2008), infrared (Werner et al 2004b;Sellgren et al 2007), and submillimetric wavelengths (Gerin et al 1998). The distance of HD 200775 is uncertain.…”

Section: Origins and Evolution Of The Csesmentioning

confidence: 99%

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The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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Context. Compact circumstellar envelopes (CSEs) have been detected around several Cepheids by interferometry. In particular, observations with the VINCI instrument revealed in 2006 a compact envelope around the long period Cepheid Car (P = 35.5 days). Another Cepheid, RS Pup (P = 41.4 days), presents a large (≈2 ) circumstellar nebula scattering the Cepheid light in the visible. These envelopes are particularly interesting for two reasons: their presence could impact the Cepheid distance scale, and they could imply stellar mass loss. Aims. Our goal is to establish the spatial and spectral properties of the CSEs of Car and RS Pup. This is done through a parametrization of the envelopes in terms of fractional flux (with respect to the star) and angular size. Methods. We retrieved archival Spitzer images of the two stars (λ = 3.5−70 μm), and obtained new diffraction-limited imaging with the VLT/VISIR camera in BURST mode (λ = 8.6−11.9 μm), as well as interferometric observations with the VLTI/MIDI beam combiner (λ = 8−13 μm). This combination of single-telescope and interferometric techniques allows us to probe the envelopes of the two Cepheids over a broad range of angular scales, from arcminutes to milliarcseconds. Results. The circumstellar envelope of RS Pup is resolved spatially at 24 and 70 μm by Spitzer, and around 10 μm by MIDI and VISIR. The envelope of Car appears much more compact, and is resolved only in the VISIR and MIDI observations. The infrared excesses we detect around RS Pup and Car are both very significant, but differ considerably in spectral and spatial properties. We detect a warm component in the CSE of both stars at a spatial scale of a few 100 to a few 1000 AU. In addition, RS Pup presents a very large (several 100 000 AU) and cold (≈40 K) dusty envelope. Conclusions. The observed properties of the CSEs lead us to propose that the cold dust content of the large reflection nebula surrounding RS Pup has an interstellar origin, while the warm CSEs of the two stars were created by ongoing stellar mass loss. We also speculate that the NGC 7023 reflection nebula surrounding the Herbig Be star HD 200775 is an analogue of RS Pup at an age of 100 000 years. The presence of CSEs around the two brightest long-period Cepheids is an indication that many long-period members of this class, if not all, could be surrounded by warm circumstellar envelopes created by mass loss. However, very large dusty envelopes such as that of RS Pup are probably less common, as according to our scenario, they require the presence of a high dust density in the interstellar medium (ISM) at the time of the formation of the Cepheid progenitor.

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Section: Origins and Evolution Of The Csesmentioning

confidence: 78%

Section: Origins and Evolution Of The Csesmentioning

confidence: 99%

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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“…Some recent models of interstellar dust have included an abiotic polycyclic aromatic hydrocarbon (PAH) component that, under appropriate circumstances, could produce a l= 2175 Å absorption band (Witt et al 2006). However, for PAHs and other complex organic molecules to form abiotically poses serious problems, in particular with the requirement that compact PAHs are in high ionization states.…”

Section: Microbial Dust and Polycyclic Aromatic Hydrocarbonsmentioning

confidence: 99%

Evidence for biodegradation products in the interstellar medium

Rauf

Wickramasinghe

2009

International Journal of Astrobiology

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: The interstellar absorption band centred on 2175 Å that is conventionally attributed to monodisperse graphite spheres of radii 0.02 mm is more plausibly explained as arising from biologically derived aromatic molecules. On the basis of panspermia models, interstellar dust includes a substantial fraction of biomaterial in various stages of degradation. We have modeled such an ensemble of degraded biomaterial with laboratory spectroscopy of algae, grass pigments, bituminous coal and anthracite. The average ulrtraviolet absorption profile for these materials is centred at 2175 Å with a full width at half maximum of 250 Å , in precise agreement with the interstellar extinction observations. Mid-infrared spectra also display general concordance with the unidentified interstellar absorption features found in a wide variety of astronomoical sources.

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“…The three PDRs at the edges of the remaining material are viewed approximately edge-on. NGC 7023 has been observed extensively in the radio (e.g., Gerin et al 1998), in H 2 lines (Lemaire et al 1999) and in the visible (e.g., Berné et al 2008;Witt et al 2006). Several infrared (IR) features were discovered with ISO and Spitzer (Cesarsky et al 1996;Werner et al 2004), in addition to strong variations in the 5-35 μm spectra explained by photo-chemical processing of the very small particles (Abergel et al 2002;Rapacioli et al 2006;Berné et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Abergel¹,

Arab²,

Compiègne

et al. 2010

A&A

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Context. In photodissociation regions (PDRs), the physical conditions and the excitation evolve on short spatial scales as a function of depth within the cloud, providing a unique opportunity to study how the dust and gas populations evolve with the excitation and physical conditions. The mapping of the PDRs in NGC 7023 performed during the science demonstration phase of Herschel is part of the "Evolution of interstellar dust" key program. The goal of this project is to build a coherent database on interstellar dust emission from diffuse clouds to the sites of star formation. Aims. We study the far-infrared/submillimeter emission of the PDRs and their fainter surrounding regions. We combine the Herschel and Spitzer maps to derive at each position the full emission spectrum of all dust components, which we compare to dust and radiative transfer models in order to learn about the spatial variations in both the excitation conditions and the dust properties. Methods. We adjust the emission spectra derived from PACS and SPIRE maps using modified black bodies to derive the temperature and the emissivity index β of the dust in thermal equilibrium with the radiation field. We present a first modeling of the NGC 7023-E PDR with standard dust properties and abundances. Results. At the peak positions, a value of β equal to 2 is compatible with the data. The detected spectra and the spatial structures are strongly influenced by radiative transfer effects. We are able to reproduce the spectra at the peak positions deduced from Herschel maps and emitted by dust particles at thermal equilibrium, and also the evolution of the spatial structures observed from the near infrared to the submillimeter. On the other hand, the emission of the stochastically heated smaller particles is overestimated by a factor ∼2.

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The Excitation of Extended Red Emission: New Constraints on Its Carrier fromHubble Space TelescopeObservations of NGC 7023

Cited by 94 publications

References 58 publications

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Evidence for biodegradation products in the interstellar medium

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

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