Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2006.08716

Revisiting the Formation of HeH$^+$ in the Planetary Nebula NGC 7027

R. C. Forrey·J. F. Babb·E. D. S. Courtney·R. McArdle·P. C. Stancil
View original source ↗Read source document ↗Export metadata ↓

Abstract

From four independent calculations using three different theoretical approaches, rate coefficients for the formation of HeH$^+$ via the radiative association of He$^+$ and H were computed. Good agreement is found between our new calculations and prior results obtained two decades ago for kinetic temperatures between $\sim$800 and 20,000 K. This finding is inconsistent with a recent claim in the literature of a wide variation in published values and establishes the robustness of our knowledge of this process for the formation of HeH$^+$. The implications of the current results to the first detection of HeH$^+$ and its modeled abundance in the planetary nebula NGC 7027 are discussed.

Explore related subjects

astro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

R. C. Forrey, J. F. Babb, E. D. S. Courtney, R. McArdle, P. C. Stancil. 2020-06-15. Revisiting the Formation of HeH$^+$ in the Planetary Nebula NGC 7027. https://doi.org/10.3847/1538-4357%2Fab9a50

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Gas Phase Distribution in the Neutral ISM: A Comparison between Observation and Numerical Simulation

The neutral hydrogen (Hi) 21-cm line serves as a powerful tracer of the neutral interstellar medium (ISM). Thermal stability analysis suggests that the neutral ISM is bistable in nature, consisting of the cold neutral medium (CNM) embedded within the warm neutral medium (WNM), both in approximate thermal pressure equilibrium. When turbulence is incorporated into the numerical simulations, a third thermally unstable medium (UNM) emerges between the CNM and the WNM. Although observational studies support the existence of this intermediate phase, a clear empirical correlation between the fraction of the UNM gas and the strength of the turbulence remains elusive. In this study, we investigate the various phases of neutral ISM using Hi 21-cm emission-absorption spectra from the publicly available GWA and LAB surveys. We compare our results with several numerical simulations, including TIGRESS-NCR and TIGRESS-CLASSIC, and find that our results are more closely consistent with TIGRESS-NCR than with TIGRESS-CLASSIC. From our observational modeling, we find that 19.8% of the gas reside in the CNM phase, 32.5% in the UNM phase, and 47.8% in the WNM phase, assuming phase boundaries defined by spin temperature: T_s < 250 K for the CNM, 250 K < T_s < 4000 K for the UNM, and T s > 4000 K for the WNM. We further expect that deep, sensitive absorption studies with the Square Kilometre Array (SKA) or the Next Generation Very Large Array (ngVLA), capable of robustly detecting WNM clouds in absorption will place more tighter observational constraints on the fraction of the gas in three different phases of the neutral ISM.

astro-ph.GA↗
arXiv2026

Spatially Resolved Nebular-Stellar Reddening with JWST/NIRISS

An accurate determination of the dust attenuation within galaxies is essential to derive key physical properties such as the star formation rate (SFR). We present an analysis using the JWST/NIRISS data from the GLASS-JWST ERS programme to investigate and characterise the stellar and nebular reddening of galaxies at $1.0<z<2.4$, down to the sub-kpc scale. We use a multiregion fitting method to extract high-quality H$α$ and H$β$ emission line maps for 99 individual galaxies across a stellar mass range $7.0<\log_{10}(M_*/\mathrm{M}_{\odot})<10.5$. We find no evidence for ratios of the Balmer decrement (H$α$/H$β$) below the intrinsic limit for Case B recombination, beyond the expected variation from observational uncertainties. We reproduce the local correlation between the Balmer decrement and total stellar mass, and find no measurable difference when splitting the sample by redshift, with negligible attenuation below $\log_{10}(M_*/\mathrm{M}_{\odot})\lesssim8.5$. Similarly, the best-fit relation between the nebular and continuum reddening follows the same relation as in local starburst galaxies, $E(B-V)_{\mathrm{SED}} = (0.46\pm0.02)E(B-V)_{\mathrm{neb}}$, together indicating no significant evolution in the dust geometry within galaxies out to $z\lesssim2.4$. We derive best-fit linear relations between the differential nebular-stellar reddening and the SED-derived star formation rate (SFR) and stellar mass, finding statistically significant relations for both quantities. We use our spatially-resolved measurements to derive an empirical calibration between the resolved differential reddening, and the SFR surface density. These will enable crucial dust attenuation corrections for spatially-resolved science at higher redshifts where the Balmer lines are inaccessible, such as with future Roman grism observations.

astro-ph.GA↗
arXiv2026

A First Measurement of Circumgalactic Dust Reddening from Only 4.6 deg$^2$ of the Rubin Observatory's Data Preview 1

We present the first measurement of circumgalactic dust reddening from the Vera C. Rubin Observatory, using only 4.6 deg$^2$ of ComCam Data Preview 1 --- roughly $0.03\%$ of the final LSST footprint. Using photometric redshifts, we stack background-galaxy colors around foreground-galaxy positions and detect a chromatic reddening profile from $r_\perp \simeq 10$ kpc to $1$ Mpc. Interpreting average $E(g-z)$ with a Milky Way extinction curve, we find $A_V = (1.3 \pm 0.4) \times 10^{-1} (r_\perp / 20 \mathrm{kpc})^{-1.8 \pm 0.4}$ within $120$ kpc. The amplitude and radial dependence agree with earlier Sloan Digital Sky Survey (SDSS), KiDS, and Dark Energy Survey (DES) results despite the $\sim1000\times$ smaller survey area and a foreground sample extending 3--6 mag fainter and 1--2 dex lower in stellar mass. The innermost 10--15 kpc bin reaches $A_V \simeq 0.3$ mag, comparable to high-latitude extinction through the Milky Way disk near the solar circle; the steep power-law slope implies a dust distribution that does not simply trace the halo-gas profile. Splitting by rest-frame $g-r$ shows stronger extinction around red foreground galaxies (rest-frame $g-r > 0.5$), although the blue subsample is too noisy to establish a significant color dependence. This red sample, with median halo mass $5 \times 10^{11} M_\odot$, shows substantially more reddening within 50 kpc than previously measured around more massive LRGs and implies a dust-to-stellar-mass ratio of $\sim 2\%$, nearly saturating the dust budget allowed by stellar metal yields. These pathfinder data demonstrate LSST's promise for high-precision galaxy--dust measurements across galaxy mass, environment, and redshift.

astro-ph.GA↗