Nu STAR ITS BACKGROUND AND CLUSTERS OF GALAXIES

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

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

THE CHALLENGE OF FOCUSING HARD X-RAYS

THE CHALLENGE OF FOCUSING HARD X-RAYS GRAZING INCIDENCE ANGLE where ρ is density (g/cm 3) and E in ke. V For example even for Pt (ρ=21 g/cm 3) at 30 ke. V is ≈ 0. 18 deg, whereas at 5 ke. V 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 Nu. STAR SATELLITE HARRISON+13

THE Nu. STAR SATELLITE CZT detectors with Cs. I anticoincidence HARRISON+13

Intra-cluster medium (ICM) Thermal plasma Relativistic particles X-rays (10 -30%) Radio Galaxies (5%) Dark Matter Gravitational potential 1 E 0657 -156 THE BULLET CLUSTER Galaxy clusters are the most massive (M~1014 -1015 MSUN) objects in the Universe

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

EXTENDED RADIO EMISSION IN CLUSTERS A 3376 Radio relics linear structures of Mpc size, usually at the outskirts of the diffuse extended emission. 20%-50% detected polarization

CONNECTION WITH CLUSTER MERGERS

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 Nu. STAR BKG § Instrumental background due to Compton scattered γrays and activation lines (passage trough SAA) § “Aperture” background § Reflection (solar + CXB) § Focused CXB

INSTRUMENTAL BKG Cs. I Fluorescence Activation Lines Continuum

APERTURE BKG

REFLECTION BKG

REFLECTION BKG Dark Earth is not Dark !

REFLECTION BKG Sunshine No sunshine

REFLECTION BKG TI LINE

THE COMPONENTS OF THE Nu. STAR BKG

Nu. STAR VIEW OF THE BULLET WIK+14

Nu. STAR VIEW OF THE BULLET: IC DETECTION NO

COMA CENTER OBSERVATION 3 -10 ke. V 10 -20 ke. V GASTALDELLO+15

COMA NUSTAR SPECTRAL ANALYSIS

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 Nu. STAR/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 Nu. STAR/pn but now for Nu. STAR/CXO The same trend is present

COMA MOSAIC N. J. Westergaard

COMA MOSAIC Dan WIK

COMA RAY TRACING SIMLATIONS N. J. Westergaard

COMING NEXT: A 523 Giovannini+11

COMING NEXT: A 523

Multiwavelength view of Abell 523. M. Girardi et al. MNRAS 2016; 456: 2829 -2847

Spatial distribution on the sky of the 80 spectroscopic cluster members and relative isodensity contour map obtained with the 2 D-DEDICA method (small black open circles and thin blue contours). M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Left panel: the azimuthally averaged brightness profile of the radio halo emission in A 523. M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Chandra image in the 0. 5– 7 ke. V energy band smoothed on a 10 arcsec scale. M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Temperature map (ke. V) showing that the northern cluster region is characterized by a higher temperature than the central and southern regions. M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published

Total halo radio power at 1. 4 GHz versus cluster X-ray luminosity in the 0. 1– 2. 4 ke. V band. M. Girardi et al. MNRAS 2016; 456: 2829 -2847 © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

SUMMARY § Nu. STAR has the capabilities to constrain well hot thermal plasmas (like the 8 -9 ke. V emission in Coma center or 14 ke. V 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.