On the metal abundance in the core of M 87

Abstract

Abstract. We revisit the XMM-Newton observation of M 87 to make a new and more detailed measurement of the metal abundance profile. After having verified that spectral fits with single temperature models show a dramatic abundance drop within 1 arcmin of the cluster core, we show that more appropriate models, which include a multi-temperature component to account for the strong temperature gradient observed in M 87, and a power-law component to account for the emission of the nucleus and knot A, give a substantially flat abundance profile. The drastic abundance decrement found by fitting a single temperature component to the data is an artifact known as "Fe-bias" (Buote 2000a,b) following from the application of an oversimplified spectral model to the data.

Abundance Gradients and the Role of Supernovae in M87

“…Given the substantial agreement between the 2T and fake multiphase models (Molendi & Gastaldello 2001), we can regard the 2T APEC results as also indicative for a fake multiphase model.…”

“…A two-temperature model (2T; vmekal+vmekal in XSPEC and model II in Molendi & Gastaldello 2001) using the plasma code MEKAL (Mewe-Kaastra-Liedahl;Mewe et al 1985;Liedahl et al 1995). This model has 15 free parameters: the temperature and the normalization of the two components and the abundance of O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, all expressed in solar units.…”

“…This model has 15 free parameters, as does the 2T model, because the maximum temperature T max is tied to the vmekal component temperature. As indicated in recent papers (Molendi & Pizzolato 2001;Molendi & Gastaldello 2001), this model is used to describe a scenario that is different from a multiphase gas, which it was written for; the gas is all at one temperature, and the multiphase appearance of the spectrum comes from the projection of emission from many different physical radii. A more correct description will be given by a real deprojection of the spectrum (F. Pizzolato et al 2002, in preparation).…”

“…The bounding radii are 0 0 -0<5, 0<5-1 0 , 1 0 -2 0 , 2 0 -3 0 , 3 0 -4 0 , 4 0 -5 0 , 5 0 -7 0 , 7 0 -9 0 , 9 0 -11 0 , and 11 0 -14 0 . The analysis of the four central regions within 3 0 was already discussed in Molendi & Gastaldello (2001).…”

GALAXY CLUSTERS IN THESWIFT/BURST ALERT TELESCOPE ERA: HARD X-RAYS IN THE INTRACLUSTER MEDIUM

“…This flux is a factor of ∼4 larger than the total cluster flux observed by BAT in the same energy band. Recently, Molendi & Gastaldello (2008) analyzed a long XMM-Newton observation and did not find evidence for nonthermal emission. According to them, the discrepancy between the Chandra and XMM-Newton results was due to a problem in the effective area calibration of Chandra.…”