A Catalog of Recombination Lines from 100 GHz TO 10 Microns

Towle, Jonathan P.; Feldman, P. A.; Watson, J. K. G.

doi:10.1086/192380

Cited by 28 publications

(34 citation statements)

References 6 publications

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“…Towle et al [204] calculated the distributions of intensities of the fine-structure components of transitions between high members of hydrogen series in the local thermodynamic equilibrium (LTE) approximation. They showed that these distributions are highly asymmetric, and their shapes vary strongly depending on the difference between the principal quantum numbers Dn.…”

Section: The Concept Of Distinctive Energiesmentioning

confidence: 99%

A critical compilation of experimental data on spectral lines and energy levels of hydrogen, deuterium, and tritium

Kramida

2010

Atomic Data and Nuclear Data Tables

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Section: The Concept Of Distinctive Energiesmentioning

confidence: 99%

A critical compilation of experimental data on spectral lines and energy levels of hydrogen, deuterium, and tritium

Kramida

2010

Atomic Data and Nuclear Data Tables

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“…The intensities of small ∆n RRLs (i.e., Hnα transition) are higher than the intensities of larger ∆n RRLs (i.e., Hnβ, Hnγ, and Hnδ transitions) (Towle et al 1996). This explains the lower detection rates of ∆n > 1 RRLs for a given sensitivity.…”

Section: Detection Ratesmentioning

confidence: 96%

ATLASGAL-selected massive clumps in the inner Galaxy

Kim

Wyrowski

Urquhart

et al. 2017

A&A

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Aims. Observations of millimeter wavelength radio recombination lines (mm-RRLs) are used to search for Hii regions in an unbiased way that is complementary to many of the more traditional methods previously used (e.g., radio continuum, far-infrared colors, maser emission). The mm-RRLs can be used to derive physical properties of Hii regions and to provide velocity information of ionized gas. Methods. We carried out targeted mm-RRL observations (39 ≤ principal quantum number (n) ≤ 65 and ∆n = 1, 2, 3, and 4, named Hnα, Hnβ, Hnγ, and Hnδ) using the IRAM 30m and Mopra 22m telescopes. In total, we observed 976 compact dust clumps selected from a catalog of ∼10,000 sources identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The sample was selected to ensure a representative mix of star-forming and quiescent clumps such that a variety of different evolutionary stages is represented. Approximately half of the clumps are mid-infrared quiet while the other half are mid-infrared bright. Results. We detected Hnα mm-RRL emission toward 178 clumps; Hnβ, Hnγ, and Hnδ were also detected toward 65, 23, and 22 clumps, respectively. This is the largest sample of mm-RRLs detections published to date. Comparing the positions of these clumps with radio continuum surveys we identified compact radio counterparts for 134 clumps, confirming their association with known Hii regions. The nature of the other 44 detections is unclear, but 8 detections are thought to be potentially new Hii regions while the mm-RRL emission from the others may be due to contamination from nearby evolved Hii regions. Broad linewidths are seen toward nine clumps (linewidth > 40 km s −1 ) revealing significant turbulent motions within the ionized gas; in the past, such wide linewidths were found toward very compact and dense Hii regions. We find that the systemic velocity of the associated dense molecular gas, traced by H 13 CO + (1−0), is consistent with the mm-RRL velocities and confirms them as embedded Hii regions. We also find that the linewidth of the H 13 CO + (1−0) emission is significantly wider than those without mm-RRL detection, indicating a physical connection between the embedded Hii region and their natal environments. We also find a correlation between the integrated fluxes of the mm-RRLs and the 6 cm continuum flux densities of their radio counterparts (the correlation coefficient, ρ, is 0.70). By calculating the electron densities we find that the mm-RRL emission is associated with Hii regions with n e <10 5 cm −3 and Hii region diameter > 0.03 pc. Conclusions. We detected mm-RRLs toward 178 clumps and identified eight new Hii region candidates. The broad mm-RRL from nine clumps may indicate that they arise in very young hyper-compact Hii regions. The mm-RRLs trace the radio continuum sources detected by high-resolution observations and their line parameters show associations with the embedded radio sources and their parental molecular clumps.

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“…These k energies have a degeneracy

g_{k, j} = \{\begin{matrix} right 2 (2 j + 1) & right j \leq k - 3 / 2 \\ right 2 j + 1 & right j = k - 1 / 2 . \end{matrix}

The fine‐structure components typically span a frequency range of the order of MHz and thus cannot individually be resolved with ALMA due to their thermal broadening in the ionized gas, which can be much larger than their separation. However, the splitting can change the line profile, and the frequencies and Einstein coefficients must be computed using relativistic quantum mechanics (Towle et al ).…”

Section: Physics Of Hydrogen Recombination Linesmentioning

confidence: 99%

“…with M n = 0.190 775, 0.026 332, 0.008 1056, 0.003 4917, 0.001 8119, 0.001 0585 for n = 1, 2, 3, 4, 5, 6, respectively. The situation is more complicated for recombination lines in the ALMA bands because lines above 100 GHz show non-negligible fine-structure splitting (Towle, Feldman & Watson 1996). For each principal quantum number k, there are k different energies which depend on the total angular momentum j = 1/2, 3/2, .…”

Section: P H Y S I C S O F H Y D Ro G E N R E C O M B I Nat I O N L Imentioning

confidence: 99%

“…The fine-structure components typically span a frequency range of the order of MHz and thus cannot individually be resolved with ALMA due to their thermal broadening in the ionized gas, which can be much larger than their separation. However, the splitting can change the line profile, and the frequencies and Einstein coefficients must be computed using relativistic quantum mechanics (Towle et al 1996). The line profile function φ ν is in general a convolution of a Gaussian profile φ G ν caused by thermal and microturbulent broadening and a Lorentzian profile φ L ν caused by electron pressure broadening (Brocklehurst & Seaton 1972).…”

Section: P H Y S I C S O F H Y D Ro G E N R E C O M B I Nat I O N L Imentioning

confidence: 99%

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Understanding hydrogen recombination line observations with ALMA and EVLA

Peters¹,

Longmore

Dullemond

2012

Monthly Notices of the Royal Astronomical Society

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Hydrogen recombination lines are one of the major diagnostics of H ii region physical properties and kinematics. In the near future, the Expanded Very Large Array (EVLA) and the Atacama Large Millimeter Array (ALMA) will allow observers to study recombination lines in the radio and submillimetre regimes in unprecedented detail. In this paper, we study the properties of recombination lines, in particular at ALMA wavelengths. We find that such lines will lie in almost every wideband ALMA set‐up and that the line emission will be equally detectable in all bands. Furthermore, we present our implementation of hydrogen recombination lines in the adaptive‐mesh radiative transfer code radmc‐3d. We particularly emphasize the importance of non‐local thermodynamical equilibrium (non‐LTE) modelling since non‐LTE effects can drastically affect the line shapes and produce asymmetric line profiles from radially symmetric H ii regions. We demonstrate how these non‐LTE effects can be used as a probe of systematic motions (infall and outflow) in the gas. We use radmc‐3d to produce synthetic observations of model H ii regions and study the necessary conditions for observing such asymmetric line profiles with ALMA and EVLA.

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A Catalog of Recombination Lines from 100 GHz TO 10 Microns

Cited by 28 publications

References 6 publications

A critical compilation of experimental data on spectral lines and energy levels of hydrogen, deuterium, and tritium

A critical compilation of experimental data on spectral lines and energy levels of hydrogen, deuterium, and tritium

ATLASGAL-selected massive clumps in the inner Galaxy

Understanding hydrogen recombination line observations with ALMA and EVLA

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