Near‐Infrared Spectroscopy of Molecular Hydrogen Emission in Four Reflection Nebulae: NGC 1333, NGC 2023, NGC 2068, and NGC 7023

Martini, Paul; Sellgren, K.; DePoy, D. L.

doi:10.1086/308040

Cited by 36 publications

(45 citation statements)

References 60 publications

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“…Fluorescent H 2 emission was first detected in the reflection nebula NGC 2023 by Gatley et al (1987). It has been also observed, for example, in other reflection nebulae (Martini et al 1999), planetary nebulae (Dinerstein et al 1988), and H ii regions such as M 16 (Allen et al 1999). Observational evidence that favors fluorescence over shock excitation includes narrow H 2 line widths (Burton et al 1990), a H 2 1-0 S(1)/2-1 S(1) ratio of ∼1.5−2.0 (Black & van Dishoeck 1987), and transitions from higher excited states (ν ∼ 7−8) (Burton et al 1992).…”

Section: Introductionmentioning

confidence: 84%

Rosette globulettes and shells in the infrared

Mäkelä

Haikala

Gahm

2014

A&A

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Context. Giant galactic H ii regions surrounding central young clusters show compressed molecular shells, which have broken up into clumps, filaments, and elephant trunks interacting with UV light from central OB stars. Tiny, dense clumps of subsolar mass, called globulettes, form in this environment. Aims. We observe and explore the nature and origin of the infrared emission and extinction in these cool, dusty shell features and globulettes in one H ii region, the Rosette nebula, and search for associated newborn stars.Methods. We imaged the northwestern quadrant of the Rosette nebula in the near-infrared (NIR) through wideband JHKs filters and narrowband H 2 1-0 S(1) and Pβ plus continuum filters using the Son of Isaac (SOFI) instrument at the New Technology Telescope (NTT) at European Southern Observatory (ESO). We used the NIR images to study the surface brightness of the globulettes and associated bright rims. We used the NIR JHKs photometry to create a visual extinction map and to search for objects with NIR excess emission. In addition, archival images from Spitzer Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 μm and Herschel Photoconductor Array Camera and Spectrometer (PACS) observations, covering several bands in the mid-infrared and far-infrared, were used to further analyze the stellar population, to examine the structure of the trunks and other shell structures and to study this Rosette nebula photon-dominated region in more detail. Results. The globulettes and elephant trunks have bright rims in the Ks band, which are unresolved in our images, on the sides facing the central cluster. An analysis of 21 globulettes, where surface brightness in the H 2 1-0 S(1) line at 2.12 μm is detected, shows that approximately a third of the surface brightness observed in the Ks filter is due to this line: the observed average of the H 2 /Ks surface brightness is 0.26 ± 0.02 in the globulettes' cores and 0.30 ± 0.01 in the rims. The estimated H 2 1-0 S(1) surface brightness of the rims is ∼3−8 × 10 −8 Wm −2 sr −1 μm −1 . The ratio of the surface brightnesses support fluorescence instead of shocks as the H 2 excitation mechanism. The globulettes have number densities of n(H 2 ) ∼ 10 −4 cm −3 or higher. We estimated masses of individual globulettes and compared them to the results from previous optical and radio molecular line surveys. We confirm that the larger globulettes contain very dense cores, that the density is also high farther out from the core, and that their mass is subsolar. Two NIR protostellar objects were found in an elephant trunk and one was found in the most massive globulette in our study.

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Section: Introductionmentioning

confidence: 84%

Rosette globulettes and shells in the infrared

Mäkelä

Haikala

Gahm

2014

A&A

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“…The proximity of this object to us and the known properties of the exciting star make it one of the best objects for studying PDRs. Observations show that this nebula hosts different gas density structures, including dense clumps (n ∼ 10 6 cm −3 ) embedded in lower density gas (n = 10 4 −10 5 cm −3 ) (Chokshi et al 1988;Sellgren, Werner & Dinerstein 1992;Fuente et al 1996;Lemaire et al 1996;Martini et al 1997;Martini et al 1999;Fuente et al 2000;Takami et al 2000;An & Sellgren 2003;Fleming et al 2010;Habart et al 2011;Kohler et al 2014;andPilleri et al 2012, 2015). At the wall of the cavity, PDR emission arises ∼42 ′′ northwest, ∼55 ′′ southwest, and ∼155 ′′ east of the central illuminating star where the FUV field intensities of G = 2600, 1500, and 250, respectively, in units of .…”

Section: Introductionmentioning

confidence: 97%

“…1986; Sellgren, Werner & Dinerstein 1992;Lemaire et al 1996;Lemaire et al 1999;Martini et al 1997;Martini et al 1999). In particular, low spectral resolution observations of H 2 emission (Martini et al 1997(Martini et al , 1999 found high density clumps in the PDR regions of NGC 7023.…”

Section: Introductionmentioning

confidence: 97%

“…Molecular hydrogen emission has been observed in reflection nebulae (e.g., NGC 2023Sellgren 1986;Hasegawa et al 1987; Burton et al 1998;Martini et al 1999;McCartney et al 1999;Habart et al 2004Habart et al , 2011Sheffer et al 2011;Fleming et al 2010), the Orion nebula (Hayashi et al 1985;Luhman & Rieke 1996;Luhman, Engelbracht, & Luhman 1998;Bertoldi et al 1999;Rosenthal et al 2000;Allers et al 2005;Habart et al 2004), M17 (Chrysostomou et al 1992Sheffer & Wolfire 2011), and in planetary nebulae (e.g., Hubble 12: Ramsay et al 1993;Hora & Latter 1996;Chrysostomou et al 1998;Marquez-Lugo et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, low spectral resolution observations of H 2 emission (Martini et al 1997(Martini et al , 1999 found high density clumps in the PDR regions of NGC 7023. In addition, Lemaire et al (1996) found small scale structure, less than 0.004 pc, based on high spatial resolution images of ν = 1-0 S(1) and S(2) rovibrational lines.…”

Section: Introductionmentioning

confidence: 99%

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Fluorescent H₂ Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

Pak

Kaplan

et al. 2017

ApJ

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We have analyzed the temperature, velocity and density of H 2 gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ≃ 45,000 with the Immersion GRating INfrared Spectrograph (IGRINS), we detected 68 H 2 emission lines within the 1 ′′ × 15 ′′ slit. The diagnostic ratios of 2-1 S(1)/1-0 S(1) is 0.41−0.56.In addition, the estimated ortho-to-para ratios (OPR) is 1.63−1.82, indicating that the H 2 emission transitions in the observed region arises mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H 2 from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of ν = 1, is that the predicted formation temperature for newly-formed H 2 should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1 ′′ × 1 ′′ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼10 5 cm −3 with a size smaller than ∼5 × 10 −3 pc embedded in lower density regions of 10 3 −10 4 cm −3 .

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Exposure time calculator for Immersion Grating Infrared Spectrograph: IGRINS

Pak

Jaffe

et al. 2015

Advances in Space Research

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We present an exposure-time calculator (ETC) for the Immersion Grating Infrared Spectrograph (IGRINS). The signal and noise values are calculated by taking into account the telluric background emission and absorption, the emission and transmission of the telescope and instrument optics, and the dark current and read noise of the infrared detector arrays. For the atmospheric transmission, we apply models based on the amount of precipitable water vapor along the line of sight to the target. The ETC produces the expected signal-to-noise ratio (S/N) for each resolution element, given the exposure-time and number of exposures. In this paper, we compare the simulated continuum S/N for the early-type star HD 124683 and the late-type star GSS 32, and the simulated emission line S/N for the H 2 rovibrational transitions from the Iris Nebula NGC 7023 with the observed IGRINS spectra. The simulated S/N from the ETC is overestimated by 40−50% for the sample continuum targets.

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Near‐Infrared Spectroscopy of Molecular Hydrogen Emission in Four Reflection Nebulae: NGC 1333, NGC 2023, NGC 2068, and NGC 7023

Cited by 36 publications

References 60 publications

Rosette globulettes and shells in the infrared

Rosette globulettes and shells in the infrared

Fluorescent H₂ Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

Exposure time calculator for Immersion Grating Infrared Spectrograph: IGRINS

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Near‐Infrared Spectroscopy of Molecular Hydrogen Emission in Four Reflection Nebulae: NGC 1333, NGC 2023, NGC 2068, and NGC 7023

Cited by 36 publications

References 60 publications

Rosette globulettes and shells in the infrared

Rosette globulettes and shells in the infrared

Fluorescent H2 Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

Exposure time calculator for Immersion Grating Infrared Spectrograph: IGRINS

Contact Info

Product

Resources

About

Fluorescent H₂ Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS