Comparison of ASCA and SAX:
The lines (or at least the FeK\alpha line) measured is being shifted towards the blue region by an amount of 50% for Perseus. We tested for PI x PHA columns and there is no change. Analysis of other clusters show a similar shift constant in value (0.009). The effects on the determination of temperatures are small. The influence on line abundances and chi-squared is significant for small z clusters, indicating that the blue-shift has a constant valuenot clear yet whether:
Perseus:
Dependence on Instrument: NOTE for PERSEUS: THERE IS A SIGNIFICANT DIFFERENCE IN CHI-SQUARED IF THE COOLING FLOW NORMALIZATIONS ARE LET FREE. A DECLINE FROM ~2.1 TO 1.6. TESTING FOR VMEKAL NORMS: THERE IS A LESS SIGNIFICANT DECLINE TO ~1.5 AND THE MECS1 HAS THE LOWEST CF NORM. TESTING FOR GAIN (LET REDSHIFT FREE):another significant change to ~1.3. cf norm get closer ~300, closer to the physical value and half the original value (z shift may be diff for MECS1) locking NORMS stills worsens the fits ~1.9. Ni abundance is very unbelievably supersolar with free redshift (possible energy dependence for the zshift?)
SAMPLE FITTINGS: ALL INSTRUMENTS, with extra absorbed cf (1.65-10keV)(norm of MECS1 is let free to vary)
MECS1, MECS2, MECS3, same as before
The cooling flow spectral model cflow in XSPEC is characterized by maximum and minimum temperatures, an abundance, a slope which parameterizes the temperature distribution of emission measures, and a normalization which is simply the cooling accretion rate. We adopted the emission measure temperature distribution that corresponds to isobaric cooling flows (zero slope) and the low cf temperature is fixed at 0.1keV
--------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value Data par par comp group 1 1 1 wabs nH 10^22 0.000 +/- -1.000 1 2 2 2 vmekal kT keV 5.863 +/- 0.9384 1 3 3 2 vmekal nH cm-3 1.000 frozen 1 4 4 2 vmekal He 1.000 frozen 1 5 5 2 vmekal C 1.000 frozen 1 6 6 2 vmekal N 0.3000 frozen 1 7 7 2 vmekal O 9.1950E-03 +/- 246.6 1 8 8 2 vmekal Ne 5.985 +/- 824.9 1 9 9 2 vmekal Na 0.4000 frozen 1 10 10 2 vmekal Mg 68.14 +/- 78.12 1 11 11 2 vmekal Al 0.4000 frozen 1 12 12 2 vmekal Si 3.962 +/- 4.029 1 13 13 2 vmekal S 1.881 +/- 1.714 1 14 14 2 vmekal Ar 1.391 +/- 1.289 1 15 14 2 vmekal Ca 1.391 = par 14 1 16 15 2 vmekal Fe 0.5801 +/- 0.2473 1 17 16 2 vmekal Ni 2.665 +/- 2.203 1 18 17 2 vmekal Redshift 1.1278E-02 +/- 0.9581E-03 1 19 18 2 vmekal Switch 1.000 frozen 1 20 19 2 vmekal norm 0.1078 +/- 0.1069 1 21 20 3 zwabs nH 10^22 0.000 +/- -1.000 1 22 17 3 zwabs redshift 1.1278E-02 = par 18 1 23 21 4 cflow slope 0.000 frozen 1 24 22 4 cflow lowT keV 0.1000 frozen 1 25 2 4 cflow highT keV 5.863 = par 2 1 26 15 4 cflow Abundanc 0.5801 = par 16 1 27 17 4 cflow Redshift 1.1278E-02 = par 18 1 28 23 4 cflow norm 339.6 +/- 64.10 1 29 1 5 wabs nH 10^22 0.000 = par 1 2 30 2 6 vmekal kT keV 5.863 = par 2 2 31 3 6 vmekal nH cm-3 1.000 = par 3 2 32 4 6 vmekal He 1.000 = par 4 2 33 5 6 vmekal C 1.000 = par 5 2 34 6 6 vmekal N 0.3000 = par 6 2 35 7 6 vmekal O 9.1950E-03 = par 7 2 36 8 6 vmekal Ne 5.985 = par 8 2 37 9 6 vmekal Na 0.4000 = par 9 2 38 10 6 vmekal Mg 68.14 = par 10 2 39 11 6 vmekal Al 0.4000 = par 11 2 40 12 6 vmekal Si 3.962 = par 12 2 41 13 6 vmekal S 1.881 = par 13 2 42 14 6 vmekal Ar 1.391 = par 14 2 43 14 6 vmekal Ca 1.391 = par 14 2 44 15 6 vmekal Fe 0.5801 = par 16 2 45 16 6 vmekal Ni 2.665 = par 17 2 46 17 6 vmekal Redshift 1.1278E-02 = par 18 2 47 18 6 vmekal Switch 1.000 = par 19 2 48 19 6 vmekal norm 0.1078 = par 20 2 49 20 7 zwabs nH 10^22 0.000 = par 21 2 50 17 7 zwabs redshift 1.1278E-02 = par 18 2 51 21 8 cflow slope 0.000 = par 23 2 52 22 8 cflow lowT keV 0.1000 = par 24 2 53 2 8 cflow highT keV 5.863 = par 2 2 54 15 8 cflow Abundanc 0.5801 = par 16 2 55 17 8 cflow Redshift 1.1278E-02 = par 18 2 56 24 8 cflow norm 310.9 +/- 63.69 2 57 1 9 wabs nH 10^22 0.000 = par 1 3 58 2 10 vmekal kT keV 5.863 = par 2 3 59 3 10 vmekal nH cm-3 1.000 = par 3 3 60 4 10 vmekal He 1.000 = par 4 3 61 5 10 vmekal C 1.000 = par 5 3 62 6 10 vmekal N 0.3000 = par 6 3 63 7 10 vmekal O 9.1950E-03 = par 7 3 64 8 10 vmekal Ne 5.985 = par 8 3 65 9 10 vmekal Na 0.4000 = par 9 3 66 10 10 vmekal Mg 68.14 = par 10 3 67 11 10 vmekal Al 0.4000 = par 11 3 68 12 10 vmekal Si 3.962 = par 12 3 69 13 10 vmekal S 1.881 = par 13 3 70 14 10 vmekal Ar 1.391 = par 14 3 71 14 10 vmekal Ca 1.391 = par 14 3 72 15 10 vmekal Fe 0.5801 = par 16 3 73 16 10 vmekal Ni 2.665 = par 17 3 74 17 10 vmekal Redshift 1.1278E-02 = par 18 3 75 18 10 vmekal Switch 1.000 = par 19 3 76 19 10 vmekal norm 0.1078 = par 20 3 77 20 11 zwabs nH 10^22 0.000 = par 21 3 78 17 11 zwabs redshift 1.1278E-02 = par 18 3 79 21 12 cflow slope 0.000 = par 23 3 80 22 12 cflow lowT keV 0.1000 = par 24 3 81 2 12 cflow highT keV 5.863 = par 2 3 82 15 12 cflow Abundanc 0.5801 = par 16 3 83 17 12 cflow Redshift 1.1278E-02 = par 18 3 84 24 12 cflow norm 310.9 = par 56 3 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 690.7968 using 538 PHA bins. Reduced chi-squared = 1.320835 for 523 degrees of freedom
0.0103<z<0.0132 TESTING INSTRUMENTS
MECS1 --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 0.000 +/- -1.000 2 2 2 vmekal kT keV 5.953 +/- 0.2130E-01 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 9.3857E-26 +/- 376.1 8 8 2 vmekal Ne 1.3439E-22 +/- 1270. 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 25.18 +/- 51.01 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 4.355 +/- 7.227 13 13 2 vmekal S 2.456 +/- 3.606 14 14 2 vmekal Ar 0.9116 +/- 1.704 15 15 2 vmekal Ca 0.000 +/- -1.000 16 16 2 vmekal Fe 0.4734 +/- 0.2653 17 17 2 vmekal Ni 1.508 +/- 2.194 18 18 2 vmekal Redshift 1.8300E-02 frozen 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 0.1434 +/- 0.2508 21 21 3 zwabs nH 10^22 0.000 +/- -1.000 22 18 3 zwabs redshift 1.8300E-02 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.953 = par 2 26 16 4 cflow Abundanc 0.4734 = par 16 27 18 4 cflow Redshift 1.8300E-02 = par 18 28 24 4 cflow norm 923.2 +/- 305.0 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 277.1722 using 179 PHA bins. Reduced chi-squared = 1.679831 for 165 degrees of freedom z Free --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 2.2725E-02 +/- 2.804 2 2 2 vmekal kT keV 5.950 +/- 0.3593E-01 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 0.5096 +/- 1388. 8 8 2 vmekal Ne 11.83 +/- 4605. 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 164.0 +/- 877.4 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 6.653 +/- 33.96 13 13 2 vmekal S 3.461 +/- 17.84 14 14 2 vmekal Ar 0.8531 +/- 5.919 15 15 2 vmekal Ca 0.000 +/- -1.000 16 16 2 vmekal Fe 0.5561 +/- 0.7411 17 17 2 vmekal Ni 4.699 +/- 24.21 18 18 2 vmekal Redshift 7.7324E-03 +/- 0.2311E-02 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 4.7978E-02 +/- 0.2802 21 21 3 zwabs nH 10^22 5.2094E-03 +/- 3.443 22 18 3 zwabs redshift 7.7324E-03 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.950 = par 2 26 16 4 cflow Abundanc 0.5561 = par 16 27 18 4 cflow Redshift 7.7324E-03 = par 18 28 24 4 cflow norm 187.0 +/- 154.3 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 188.0645 using 179 PHA bins. Reduced chi-squared = 1.146734 for 164 degrees of freedom 18 6.145507E-03 1.020954E-02 MECS2 --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 0.000 +/- -1.000 2 2 2 vmekal kT keV 5.955 +/- 0.1373E-01 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 0.000 +/- -1.000 8 8 2 vmekal Ne 0.000 +/- -1.000 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 77.40 +/- 53.25 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 4.544 +/- 2.523 13 13 2 vmekal S 1.437 +/- 0.9634 14 14 2 vmekal Ar 2.974 +/- 2.359 15 15 2 vmekal Ca 1.634 +/- 1.727 16 16 2 vmekal Fe 0.5717 +/- 0.2630E-01 17 17 2 vmekal Ni 1.986 +/- 1.206 18 18 2 vmekal Redshift 1.8300E-02 frozen 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 0.1100 +/- 0.7584E-01 21 21 3 zwabs nH 10^22 0.000 +/- -1.000 22 18 3 zwabs redshift 1.8300E-02 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.955 = par 2 26 16 4 cflow Abundanc 0.5717 = par 16 27 18 4 cflow Redshift 1.8300E-02 = par 18 28 24 4 cflow norm 833.1 +/- 46.36 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 206.3710 using 179 PHA bins. Reduced chi-squared = 1.250733 for 165 degrees of freedom z Free --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 0.000 +/- -1.000 2 2 2 vmekal kT keV 5.935 +/- 4.310 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 1.563 +/- 1456. 8 8 2 vmekal Ne 2.3852E-15 +/- 0.1010E+05 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 110.0 +/- 677.8 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 4.836 +/- 27.13 13 13 2 vmekal S 1.479 +/- 6.149 14 14 2 vmekal Ar 3.702 +/- 18.61 15 15 2 vmekal Ca 2.119 +/- 10.12 16 16 2 vmekal Fe 0.6041 +/- 1.296 17 17 2 vmekal Ni 2.555 +/- 10.32 18 18 2 vmekal Redshift 1.4189E-02 +/- 0.2110E-02 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 8.4973E-02 +/- 0.4318 21 21 3 zwabs nH 10^22 0.000 +/- -1.000 22 18 3 zwabs redshift 1.4189E-02 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.935 = par 2 26 16 4 cflow Abundanc 0.6041 = par 16 27 18 4 cflow Redshift 1.4189E-02 = par 18 28 24 4 cflow norm 512.4 +/- 448.8 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 193.8991 using 179 PHA bins. Reduced chi-squared = 1.182312 for 164 degrees of freedom 18 1.310842E-02 1.657495E-02 MECS3 --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 0.000 +/- -1.000 2 2 2 vmekal kT keV 5.955 +/- 0.2539E-01 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 0.1857 +/- 209.7 8 8 2 vmekal Ne 3.958 +/- 681.1 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 40.88 +/- 84.62 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 4.182 +/- 7.427 13 13 2 vmekal S 2.070 +/- 2.946 14 14 2 vmekal Ar 1.526 +/- 2.030 15 15 2 vmekal Ca 0.8265 +/- 1.067 16 16 2 vmekal Fe 0.5895 +/- 0.4849 17 17 2 vmekal Ni 2.207 +/- 3.677 18 18 2 vmekal Redshift 1.8300E-02 frozen 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 0.1528 +/- 0.2979 21 21 3 zwabs nH 10^22 0.000 +/- -1.000 22 18 3 zwabs redshift 1.8300E-02 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.955 = par 2 26 16 4 cflow Abundanc 0.5895 = par 16 27 18 4 cflow Redshift 1.8300E-02 = par 18 28 24 4 cflow norm 725.6 +/- 281.6 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 265.4565 using 180 PHA bins. Reduced chi-squared = 1.599136 for 166 degrees of freedom z Free --------------------------------------------------------------------------- --------------------------------------------------------------------------- mo = wabs[1]( vmekal[2] + zwabs[3]( cflow[4] ) ) Model Fit Model Component Parameter Unit Value par par comp 1 1 1 wabs nH 10^22 1.6069E-02 +/- 1.744 2 2 2 vmekal kT keV 5.955 +/- 0.3670E-01 3 3 2 vmekal nH cm-3 1.000 frozen 4 4 2 vmekal He 1.000 frozen 5 5 2 vmekal C 1.000 frozen 6 6 2 vmekal N 0.3000 frozen 7 7 2 vmekal O 4.068 +/- 910.3 8 8 2 vmekal Ne 24.82 +/- 2873. 9 9 2 vmekal Na 0.4000 frozen 10 10 2 vmekal Mg 122.7 +/- 571.8 11 11 2 vmekal Al 0.4000 frozen 12 12 2 vmekal Si 7.584 +/- 33.43 13 13 2 vmekal S 2.762 +/- 10.50 14 14 2 vmekal Ar 1.678 +/- 5.977 15 15 2 vmekal Ca 0.4879 +/- 2.911 16 16 2 vmekal Fe 0.6965 +/- 1.053 17 17 2 vmekal Ni 5.577 +/- 24.50 18 18 2 vmekal Redshift 1.0756E-02 +/- 0.1864E-02 19 19 2 vmekal Switch 1.000 frozen 20 20 2 vmekal norm 6.5477E-02 +/- 0.3224 21 21 3 zwabs nH 10^22 4.6130E-02 +/- 2.550 22 18 3 zwabs redshift 1.0756E-02 = par 18 23 22 4 cflow slope 0.000 frozen 24 23 4 cflow lowT keV 0.1000 frozen 25 2 4 cflow highT keV 5.955 = par 2 26 16 4 cflow Abundanc 0.6965 = par 16 27 18 4 cflow Redshift 1.0756E-02 = par 18 28 24 4 cflow norm 290.9 +/- 236.0 --------------------------------------------------------------------------- --------------------------------------------------------------------------- Chi-Squared = 198.4174 using 180 PHA bins. Reduced chi-squared = 1.202529 for 165 degrees of freedom 18 8.912099E-03 1.192250E-02--------------------------------------------------------------------------------
Dear BeppoSax team, We have analyzed BeppoSax archival data of 10 galaxy clusters, and have found what appears to be a problem in the channel to energy conversion of BeppoSax. For all 10 clusters, the measured redshift as determined from spectral fits (mainly from the Fe K line) of the data are less than the optically-determined redshifts, sometimes significantly so. Has this effect been reported previously? Do you have any idea what the nature of this problem is? We have constructed a web page describing in detail this effect we have encountered, which includes plots of measured vs. true redshifts for the sample. The web page is located at ftp://astro.lsa.umich.edu/pub/zsax.html -------------------------------------------------------------------------------- What you found in your analysis is basically correct, at 6.6 keV there is a systematic shift of 45-50 eV in the MECS E-PI conversion. you can see this for example on the Cas-A data, look at the page http://www.sdc.asi.it/software/cookbook/cross_cal.html if you look at the energies of the Cas-A iron He-like line you can see that this line is detected at 6.6 keV by the LECS, 6.59 keV by the ASCA SIS but at slighly higher energies by the three MECS units. MECS1 is the worse unit in this respect, the one with the largest shift. The present MECS resolution matrix and the MECS gain calibration where produced in the summer 1997, and tested using observations of Crab, Cas-A, Virgo and Perseus clusters. The calibration produces nice fits to the Crab spectra although the still imperfect estimation of iron features that you noticed. The next release of software and calibration is foreseen for next November-December. The MECS team is working on the issue and an improved resolution matrix may be issued for that date (it is not decided yet though). My advice for the meantime is therefore to let the redshift of the object to be free to vary when fitting MECS cluster data and be aware of this energy shift. If you need more information/clarification please don't esitate to write to me: fiore@head-cfa.harvard.edu till July 27th or fiore@chianti.sdc.asi.it or fiore@quasar.mporzio.astro.it You may also contact Silvano Molendi of the MECS team (silvano@ifctr.mi.cnr.it). He is involved in several MECS cluster observations. Thanks again for your report, Regards, Fabrizio Fiore--------------------------------------------------------------------------------------