J/ApJ/682/821 Spectral fits of galaxy clusters in X-ray (Cavagnolo+, 2008)
Bandpass dependence of X-ray temperatures in galaxy clusters. Cavagnolo K.W., Donahue M., Voit G.M., Sun M. <Astrophys. J., 682, 821-834 (2008)> =2008ApJ...682..821C
ADC_Keywords: Clusters, galaxy ; X-ray sources ; Spectroscopy Keywords: catalogs - cosmology: observations - galaxies: clusters: general - methods: data analysis - X-rays: galaxies: clusters Abstract: We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM) for 192 well-observed galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broadband (0.7-7.0keV) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0-7.0keV) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broadband spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broadband temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise ratio (S/N) to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7-7.0keV (broad) and when the energy range is 2.0/(1+z)-7.0keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broadband temperature. On further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broadband temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components (TX=0.5-3.0keV) with emission measures ≥10-30% of the primary hot component. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 80 244 Summary of sample table2.dat 120 166 Summary of excised R2500 spectral fits table3.dat 120 192 Summary of excised R5000 spectral fits
See also: B/chandra : The Chandra Archive Log (CXC, 1999-) J/ApJ/412/479 : Intracluster gas temperatures catalog (David+, 1993) J/ApJ/504/27 : The LX-T Relation for Nearby Clusters (Markevitch, 1998) J/PASJ/56/965 : X-ray properties of ASCA objects (Fukazawa+, 2004) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Name Cluster name (1) 23 A1 --- f_Name [di] Note on cluster (2) 25- 29 I5 --- ObsID Chandra observation identification number 31- 32 I2 h RAh Cluster center hour of Right Ascension (J2000) 34- 35 I2 min RAm Cluster center minute of Right Ascension (J2000) 37- 42 F6.3 s RAs Cluster center second of Right Ascension (J2000) 44 A1 --- DE- Cluster center sign of the Declination (J2000) 45- 46 I2 deg DEd Cluster center degree of Declination (J2000) 48- 49 I2 arcmin DEm Cluster center arcminute of Declination (J2000) 51- 55 F5.2 arcsec DEs Cluster center arcsecond of Declination (J2000) 57- 61 F5.1 ks ExpT Exposure time 63- 64 A2 --- Mode Observing mode 66- 67 A2 --- ACIS ACIS CCD location of centroid 69- 73 F5.3 --- z Redshift taken from Horner, 2001PhDT........88H (all redshifts confirmed with NED) 75- 80 F6.2 10+37W Lbol Bolometric luminosity in units of 10+44erg/s
Note (1): For clusters with multiple observations, the X-ray centers differ by <0.5kpc. Note (2): Flags as follows: d = cluster analyzed within R5000 only. i = cluster which was excluded from our analysis (discussed in Section 5.1).
Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 18 A18 --- Name Cluster name (1) 19 A1 --- n_Name [*] Indicates multiple observations 21- 22 I2 kpc Rc Excluded core region size 24- 26 I3 kpc Rad Cluster radius (2) 28- 32 F5.2 10+20/cm2 NHI Galactic neutral hydrogen column density 34- 37 F4.2 10+20/cm2 E_NHI ? Upper limit uncertainty in NHI 39- 42 F4.2 10+20/cm2 e_NHI ? Lower limit uncertainty in NHI 44- 48 F5.2 keV T77 Best fit 0.7-7keV MeKaL temperature 50- 54 F5.2 keV E_T77 Upper limit uncertainty in T77 56- 59 F4.2 keV e_T77 Lower limit uncertainty in T77 61- 65 F5.2 keV T27 Best fit 2-7keV MeKaL temperature 67- 71 F5.2 keV E_T27 Upper limit uncertainty in T27 73- 76 F4.2 keV e_T27 Lower limit uncertainty in T27 78- 81 F4.2 --- THBR The T77/T22 ratio 83- 86 F4.2 --- E_THBR Upper limit uncertainty in THBR 88- 91 F4.2 --- e_THBR Lower limit uncertainty in THBR 93- 96 F4.2 Sun Z77 Best-fit 0.7-7keV MeKaL abundance 98-102 F5.2 Sun E_Z77 Upper limit uncertainty in Z77 104-107 F4.2 Sun e_Z77 Lower limit uncertainty in Z77 109-112 F4.2 --- chi77 Reduced χ2 for best-fit 0.7-7keV model 114-117 F4.2 --- chi27 Reduced χ2 for best-fit 2-7keV model 119-120 I2 % Src Percentage of emission attributable to source
Note (1): Each observation has an independent spectrum extracted along with an associated WARF, WRMF, normalized background spectrum, and soft residual. Each independent spectrum is then fit simultaneously with the same spectral model to produce the final fit. Note (2): R2500 for table2: cluster radius where average cluster density is 2500x the Universe critical density or R5000 for table3.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Nov-2010
|The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line|