NuSTAR, ITS BACKGROUND AND CLUSTERS OF GALAXIES FABIO GASTALDELLO INAF, IASF-Milano And The Galaxy Clusters NuSTAR Team

OUTLINE  The NuSTAR satellite and its focusing capabilities in the hard X-ray band  NuSTAR science with galaxy clusters: IC emission and very hot thermal emission  The components of the NuSTAR background  First results on galaxy clusters

THE CHALLENGE OF FOCUSING HARD X-RAYS

GRAZING INCIDENCE ANGLE where ρ is density (g/cm 3 ) and E in keV For example even for Pt (ρ=21 g/cm 3 ) at 30 keV is ≈ 0.18 deg, whereas at 5 keV is ≈ 1.1 deg A eff f 2 x α 2 x R 2 Valid for Wolter I optics, where f focal length and R reflectivity (de Korte 1988) THE CHALLENGE OF FOCUSING HARD X-RAYS

Multi-layers: grazing incidence + Bragg reflection N layers of heavy element/ light elements (high/low refractive index as W/Si or Pt/C) with spacing d which is a function of depth (e.g, Christensen et al. 1991) THE CHALLENGE OF FOCUSING HARD X-RAYS

THE NuSTAR SATELLITE HARRISON+13

THE NuSTAR SATELLITE HARRISON+13

THE NuSTAR SATELLITE HARRISON+13 CZT detectors with CsI anticoincidence

Galaxy clusters are the most massive (M~ M SUN ) objects in the Universe Galaxies (5%) Intra-cluster medium (ICM) Thermal plasma X-rays (10-30%) Dark Matter Gravitational potential 1E THE BULLET CLUSTER Relativistic particles Radio

EXTENDED RADIO EMISSION IN CLUSTERS Radio halos fill the volume of the clusters, Mpc extension. Given the short synchrotron lifetime electrons can’t simply diffuse. No detected polarization Coma cluster

Radio relics linear structures of Mpc size, usually at the outskirts of the diffuse extended emission. 20%-50% detected polarization A3376 EXTENDED RADIO EMISSION IN CLUSTERS

CONNECTION WITH CLUSTER MERGERS

Radio halo bimodality of clusters: only luminous massive mergers have radio halos (strong support for primary models, i.e. reaccelerated electrons, not electrons produces in p-p collisions, i.e. “secondary models).

CONNECTION WITH CLUSTER MERGERS

IC IN GALAXY CLUSTERS

VERY HOT GAS IN GALAXY CLUSTERS

THE COMPONENTS OF THE NuSTAR BKG  Instrumental background due to Compton scattered γ-rays and activation lines (passage trough SAA)  “Aperture” background  Reflection (solar + CXB)  Focused CXB

INSTRUMENTAL BKG Continuum CsI Fluorescence Activation Lines

APERTURE BKG

REFLECTION BKG

Dark Earth is not Dark !

REFLECTION BKG Sunshine No sunshine

REFLECTION BKG TI LINE

THE COMPONENTS OF THE NuSTAR BKG

BULLET NuSTAR VIEW OF THE BULLET WIK+14

BULLET NuSTAR VIEW OF THE BULLET WIK+14

BULLET: NO IC DETECTION NuSTAR VIEW OF THE BULLET: NO IC DETECTION

COMA CENTER OBSERVATION 3-10 keV10-20 keV GASTALDELLO+15

COMA NUSTAR SPECTRAL ANALYSIS

COMA TEMPERATURE MAP GASTALDELLO+15

COMA TEMPERATURE MAP GASTALDELLO+15

COMA THERMODYNAMIC MAPS “Entropy” = T/EM 1/3 “Pressure”=T EM 1/2 GASTALDELLO+15

CONSTRAINTS ON IC 90% upper limit no more stringent than recent results with non-imaging instruments. Mosaic more useful than central bright pointing

GHOST RAYS Ratio of fluxes NuSTAR/pn. In black individual points, in red weighted average of sets of 6 region. A trend with distance from the optical axis is evident

GHOST RAYS Same plot as for NuSTAR/pn but now for NuSTAR/CXO The same trend is present

COMA MOSAIC N.J. Westergaard

COMA MOSAIC Dan WIK

COMA RAY TRACING SIMLATIONS N.J. Westergaard

SOLAR BKG ON COMA 7 Light curve in the 3-10 keV band

SOLAR BKG ON COMA 7 DETA Spectral range extended to 2 keV just for plotting Unfiltered Filtered No sunshine

SUMMARY  NuSTAR has the capabilities to constrain well hot thermal plasmas (like the 8-9 keV emission in Coma center or 14 keV in the Bullet). Still no luck for IC emission but stringent upper limits.  The established knowledge of the background is ok, effort still needed for a thorough understanding.

NUSTAR SENSITIVITY

NUSTAR METROLOGY SYSTEM

NUSTAR VIGNETTING

OVERLAP WITH COMA7 48

RESULTS FOR COMA7 Mean of the ratio of norm in A 1.28 with stdev 0.27 Mean of B 1.35 with stdev

RESULTS FOR COMA7 Mean of the ratio of T in A 0.96 with stdev 0.14 Mean of B 0.87 with stdev

BKG SYSTEMATICS

As expected the norm of the aperture background is not constrained by the likelihood, we need the prior

CONSTRAINING SHOCK TEMPERAUTRE IN THE BULLET Dan WIK

CONSTRAINING SHOCK TEMPERAUTRE IN THE BULLET Dan WIK

CONSTRAINING SHOCK TEMPERAUTRE IN THE BULLET Dan WIK