Collisional Plasma Models with APEC/APED: Emission-Line Diagnostics of Hydrogen-like and Helium-like Ions

By Randall K. Smith, N. Brickhouse, D. Liedahl, J. C. Raymond. 2001

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New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of high-resolution X-ray spectra in which hydrogen- and helium-like ions are usually strong features. We present results from a new collisional-radiative plasma code, the Astrophysical Plasma Emission Code (APEC), which uses atomic data in the companion Astrophysical Plasma Emission Database (APED) to calculate spectral models for hot plasmas. APED contains the requisite atomic data such as collisional and radiative rates, recombination cross sections, dielectronic recombination rates, and satellite line wavelengths. We compare the APEC results to other plasma codes for hydrogen- and helium-like diagnostics and test the sensitivity of our results to the number of levels included in the models. We find that dielectronic recombination with hydrogen-like ions into high (n = 6-10) principal quantum numbers affects some helium-like line ratios from low-lying (n = 2) transitions.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7e01887ae1ba3a134b5bead862c63b53cc67f5bb

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Citations in the corpus

Elemental Abundances and Post-Coronal Mass Ejection Current Sheet in a Very Hot Active Region (2002, methodology): “For the Ne ix 1248 line we used the calculation from the APEC/APED code (Smith et al. 2001).”
DO HOT HALOS AROUND GALAXIES CONTAIN THE MISSING BARYONS? (2010, methodology): “Using our assumed metallicity of 0.2 Z , we recalculated the emissivity using the XSPEC utility with an APEC model (Smith et al. 2001) and all other parameters matched to the observations in Kuntz & Snowden (2000), which makes these halo masses increase by 190%.”
DETECTION OF AN UNIDENTIFIED EMISSION LINE IN THE STACKED X-RAY SPECTRUM OF GALAXY CLUSTERS (2014, methodology): “To determine the best-fit cluster redshifts for each observation (given in Table 1), the cluster spectra were fit with a standard absorbed multi-temperature collisional equilibrium plasma model (apec) (Smith et al. 2001) and AtomDB v2.”
Physics of Solar Prominences: I—Spectral Diagnostics and Non-LTE Modelling (2010, background): “by Tousey et al. (1965). No prominence spectrum in the Lyman series was obtained.”
The EAGLE project: Simulating the evolution and assembly of galaxies and their environments (2014, methodology): “Mean X-ray temperatures and elemental abundances within R500,hse are determined by fitting APEC models to a single radial bin.”
The Compact, Conical, Accretion-Disk Warm Absorber of the Seyfert 1 Galaxy NGC 4051 and Its Implications for IGM-Galaxy Feedback Processes (2007, methodology): “…of NGC 4051 with two absorbing components, and use a spectral model (PHASE, Krongold et al 2003) that includes more than 3000 bound-free and bound-bound X-ray transitions from many metals (obtained mainly from the ATOMDB database, Smith et al. 2001) to derive their equivalent H column densities.”
Chandra HETGS Multiphase Spectroscopy of the Young Magnetic O Star θ1 Orionis C (2005, background): “See Smith et al. (2001) and references therein. where vth = √ 2kT m is the thermal broadening component and ξ is the rms of the turbulent velocities. ξ is used simply as a standard means of parameterizing the component of the line width caused by non-thermal bulk motion (assumed to be Gaussian).”
XMM—Newton observations of the Perseus cluster — II. Evidence for gas motions in the core (2003, methodology): “On the other hand, the most recent APEC v1.”
A deeper X‐ray study of the core of the Perseus galaxy cluster: the power of sound waves and the distribution of metals and cosmic rays (2007, methodology): “The data were fitted using a model made up of APEC thermal components at fixed temperatures of 0.5, 1, 2, 3, 4 and 8 keV, plus a = 2 power law, all absorbed by a PHABS photoelectric absorber.”
THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, methodology): “Our approach to filling in this observationally inaccessible gap is to employ a coronal model from 50 – 100 Å (a single or two-temperature APEC model, Smith et al. 2001) and models of solar active regions from 100 – 1170 Å (Fontenla et al. 2011; Linsky et al. 2014).”
The Milky Way’s Kiloparsec-Scale Wind: A Hybrid Cosmic-Ray and Thermally Driven Outflow (2007, methodology): “First, to calculate the emissivity per emission measure, the emission codes “ATOMDB” and “APEC” (Smith et al. 2001) were used to generate spectra for a range of temperatures5 5 As noted on their website (http://cxc.harvard.edu/ atomdb/), APEC is not complete below about 0.25 keV, but that will not…”
The stellar rotation–activity relationship in fully convective M dwarfs (2018, methodology): “The spectra were compared to APEC (Smith et al. 2001) singletemperature models (Raymond & Smith 1977) in collisional ionization equilibrium and absorbed by a hydrogen column using the TBABS XSPEC model (Balucinska-Church & McCammon 1992).”
Estimation of the XUV radiation onto close planets and their evaporation (2011, methodology): “(a) Line fluxes in erg cm−2 s−1. λmodel (Å) is the APED model wavelength corresponding to the measured line. logTmax indicates the maximum temperature (K) of formation of the line (unweighted by the EMD).”
THE CHANDRA SOURCE CATALOG (2009, methodology): “For detailed X-ray spectral-line modeling, the Raymond & Smith (1977) models have been superseded by more recent Xray plasma models (e.g., Mewe et al. 1995; Smith et al. 2001).”
The XMM-Newton Wide-Field Survey in the COSMOS Field: Statistical Properties of Clusters of Galaxies (2006, methodology): “…conversion in the 0.5–2 keV band excluding the lines is 1.59 × 10−12 for pn and 5.41 × 10−12 for each MOS detector, calculated for the source spectrum, corresponding to the APEC (Smith et al. 2001) model for a collisional plasma of 2 keV temperature, 1/3 solar abundance and a redshift of 0.2.”
Creation of cosmic structure in the complex galaxy cluster merger Abell 2744 (2011, methodology): “6.0q (Arnaud 1996) and we adopt Vapec thermal emission model from atomic data in the companion Astrophysical Plasma Emission Database (Smith et al. 2001), allowing for the variation of several individual elemental abundances during the spectral fittings.”
X-ray spectroscopy of galaxy clusters: studying astrophysical processes in the largest celestial laboratories (2009, methodology): “Usually two plasma models are used for fitting cluster spectra: MEKAL (Mewe et al. 1985, 1986; Kaastra 1992; Liedahl et al. 1995) and APEC (Smith et al. 2001).”
CONSTRAINING THE MILKY WAY'S HOT GAS HALO WITH O vii AND O viii EMISSION LINES (2014, methodology): “The Galactic continuum included an absorbed APEC thermal plasma model (Smith et al. 2001) with the oxygen Kα emission disabled (Lei et al. 2009).”