J/ApJ/857/59 Spitzer/IRS observations of the Galactic Center (Simpson, 2018) ================================================================================ Spitzer Infrared Spectrograph observations of the Galactic Center: quantifying the Extreme Ultraviolet/Soft X-ray fluxes. Simpson J.P. =2018ApJ...857...59S ================================================================================ ADC_Keywords: Galactic center; Spectra, infrared; Interstellar medium Keywords: Galaxy: center; X-rays: ISM; infrared: ISM; H II regions; ISM: abundances; ISM: bubbles Abstract: It has long been shown that the extreme ultraviolet spectrum of the ionizing stars of HII regions can be estimated by comparing the observed line emission to detailed models. In the Galactic Center (GC), however, previous observations have shown that the ionizing spectral energy distribution (SED) of the local photon field is strange, producing both very low excitation ionized gas (indicative of ionization by late O stars) and also widespread diffuse emission from atoms too highly ionized to be found in normal HII regions. This paper describes the analysis of all GC spectra taken by Spitzer's Infrared Spectrograph and downloaded from the Spitzer Heritage Archive. In it, HII region densities and abundances are described, and serendipitously discovered candidate planetary nebulae, compact shocks, and candidate young stellar objects are tabulated. Models were computed with Cloudy, using SEDs from Starburst99 plus additional X-rays, and compared to the observed mid-infrared forbidden and recombination lines. The ages inferred from the model fits do not agree with recent proposed star formation sequences (star formation in the GC occurring along streams of gas with density enhancements caused by close encounters with the black hole, Sgr A*), with Sgr B1, Sgr C, and the Arches Cluster being all about the same age, around 4.5Myr old, with similar X-ray requirements. The fits for the Quintuplet Cluster appear to give a younger age, but that could be caused by higher-energy photons from shocks from stellar winds or from a supernova. Description: The observations were taken with the Spitzer IRS in Cycles 1 and 4 and were downloaded from the Spitzer Heritage Archive. The spectra from programs 3295 (line fluxes published in Simpson+ 2007, J/ApJ/670/1115) and 0018 (mentioned in Simpson+ but published in this paper) were reduced and calibrated with the Spitzer S13.2 pipeline; all other data were reduced and calibrated with the final version of the pipeline, S18.18. SH and LH spectra are found in programs 0018, 3295, and 40230, and SL and LL spectra are found in programs 3121, 3189, 3616, and 40230. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 127 7249 *Intensities of lines observed with the Short-Low Module, Second Order (SL2) table3.dat 107 13651 *Intensities of lines observed with the Short-Low Module, First Order (SL1) table4.dat 256 540 *Intensities of lines observed with the Short-High Module (SH) table5.dat 127 12955 *Intensities of lines observed with the Long-Low Module, Second Order (LL2) table6.dat 147 12534 *Intensities of lines observed with the Long-Low Module, First Order (LL1) table7.dat 176 540 *Intensities of lines observed with the Long-High Module (LH) table8.dat 93 26 Positions with measured high-excitation [NeV] table9.dat 55 44 Positions with substantial high-excitation [OIV] but no measured [NeV] table10.dat 64 24 Positions with measured [SI] table11.dat 51 23 Sources with ice absorption features at 6.0 and 6.8um -------------------------------------------------------------------------------- Note on table*.dat: From erratum published in 2019, ApJ, 870, 140. -------------------------------------------------------------------------------- See also: VI/64 : Recombination line intensities for hydrogenic ions (Storey+ 1995) J/ApJ/581/258 : Infrared photometry in the Arches Cluster (Figer+, 2002) J/A+A/418/363 : Effective collision strengths for Cl II (Tayal+, 2004) J/ApJS/155/421 : Survey of Galactic Center region at 20cm (Yusef-Zadeh+, 2004) J/ApJS/165/173 : Chandra sources in Galaxy central 150pc (Muno+, 2006) J/ApJS/162/346 : Abundance gradients in the Galaxy (Rudolph+, 2006) J/A+A/453/535 : Classification of bright mid-IR sources (Schuller+, 2006) J/ApJ/661/801 : Survey for ionization in neutral gas gal. III. (Oey+, 2007) J/ApJ/670/1115 : IRS spectra at 38 positions in GC (Simpson+, 2007) J/ApJ/656/770 : Mid-IR spectrum of star-forming galaxies (Smith+, 2007) J/ApJ/693/1821 : The Spitzer infrared nearby galaxies survey (Dale+, 2009) J/ApJS/181/110 : Galactic center X-ray sources (Muno+, 2009) J/A+A/500/1253 : Electron-impact excitation of ArIII (Munoz Burgos+, 2009) J/A+A/495/157 : Interstellar extinction in GC (Schultheis+, 2009) J/ApJ/736/133 : Spitzer-IRS study of massive YSOs in GC (An+, 2011) J/MNRAS/417/114 : HST/NICMOS Galactic Center survey catalogue (Dong+, 2011) J/ApJ/737/73 : Infrared extinction toward the Galactic Centre (Fritz+, 2011) J/A+A/537/A146 : Stellar models with rotation. 0.8