Opening New Windows on Dark Matter in the X-ray Sky Kerstin Perez A Rainbow of Dark Sectors ACP Winter Workshop March 22, 2021 * Photo from 33 km up in the air! Prototype GAPS balloon flight, June 2012 See poster: Field Rogers “Low-energy Cosmic Antinuclei for Dark Matter” The sky from low to high-energy Optical, IR, UV: X-rays: Gamma-rays: FERMI HUBBLE NuSTAR + CHANDRA HESS CHANDRA HUBBLE + SPITZER Accreting black holes, Stars and gas white dwarfs, neutron stars; Pulsars, supernovae, supernovae, very hot gas, active galactic nuclei scattering by cosmic rays K. Perez - MIT 2 NuSTAR: first focusing high-energy X-ray telescope Launched June 2012 1. Two co-aligned, multilayer coated, grazing incidence focusing optics 3. CdZnTe pixel detector spectrometers 2. Deployable 10 m mast Harrison+ (2013) arxiv:1301.7307 3 NuSTAR: first focusing high-energy X-ray telescope • Energy Band: 3-79 keV • Angular Resolution: 58” (HPD), 18” (PSF) • Field-of-view: 12’ x 12’ • Energy resolution (FWHM): 0.4 keV at 6 keV, 0.9 keV at 60 keV • Temporal resolution: 0.1 ms • Maximum Flux Rate: 10k ct/s • ToO response: <24 hours Harrison+ (2013) arxiv:1301.7307 4 Focus on the Galactic Center • High density of both astrophysical X- rays and dark matter 2° INTEGRAL E = 20-40 keV E = 10-40 keV >2 Ms exposure 1.5° G. Belanger, et al. (2006) K. Mori+ (2015) arxiv:1510.04631 5 K. Mori+ (2015) arxiv:1510.04631 Massive, magnetically accreting population in the central ~10 pc 10-20 keV Perez+ Nature (2015) XMM Fe-Ka contours Echoes of X-ray, cosmic-ray Field Rogers injection in molecular clouds? (NSF grad fellow) F. Rogers et al. (in prep.) Constraining stellar remnant populations in galactic nuclei Hong+ (2016) arXiv:1605.03882 K. Perez - MIT 6 Adapting NuSTAR as a large-aperture DM telescope • “0-bounce” photons that bypass the optics are typically a major background 3.5 deg • Novel analysis exploits >10x increase in efficiency for slowly-varying, diffuse signal • Expands energy range up to 160 keV 0.2 0.4 0.6 0.8 • High-resolution, small field-of-view (0.05deg2), snapshots of the sky 7 X-rays from sterile neutrino dark matter Neutrino Minimal Standard Model 3 light SM neutrinos 3 sterile neutrinos: • only interact via neutrino oscillations • two heavy (>100 GeV) explain oscillations • one lighter (~keV) can account for DM Sterile neutrino decay can provide a clear X-ray line signature 8 The sterile neutrino landscape Only a narrow window remains in which sterile neutrinos (in the simplest models) can constitute all of dark matter Require *model- More mixing momentum independent with standard distribution not Abazajian, Fuller neutrinos & Patel 2001; underproduce KA 2005 small-scale structure Require correct dark matter Less mixing with abundance standard produced in the neutrinos early universe 9 …the “3.5 keV line”? 1. A faint line detected in XMM-Newton 2. Line consistent with observations using spectra of stacked galaxy clusters many instruments and astrophysical regions Bulbul+ (2014) 10 …the “3.5 keV line”? 1. A faint line detected in XMM-Newton 2. Line consistent with observations using spectra of stacked galaxy clusters many instruments and astrophysical regions Bulbul+ (2014) 3. Ruled out using full ~550Ms XMM-Newton data catalog? Foster+ (2021) Dessert+ Science (2020) 11 Perez, Ng, Beacom+ (2017) The Galactic Center/Bulge (+) Large dark matter density (+) Large sensitivity from unfocused FOV (–) Galactic ridge emission incl. bright Fe lines Perez, Ng, Beacom+ (2017) K. Ng, Roach, Perez+ (2019) M31 (Andromeda Galaxy) 105 FPMA FPMB 105 FPMA FPMB )] 1 − )] 1 − 104 M31 (Andromeda Galaxy) 104 (cts keV ⇥ Inst. + solar (cts keV Inst. + solar 103 ⇥ Inst. + solar 0-b CXB Inst. + solar 0-b CXB 3 [keV 10 0-b CXB 0-b CXB [keV dE dN 2-b M31 2-b M31 E 2-b CXB 2-b CXB dE dN 2-b M31 2-b M31 2 E 2-b CXB 2-b CXB 10 1 2 102 10 10 1.2 101 102 1.0 1.2 0.8 1.0 0.8 Data / Model 0.6 1 2 1 2 10 Data / Model 0.6 10 10 10 1 2 1 2 10 E[keV] 10 10 10 E[keV] (+) No Fe emission lines (+) surveys dark matter from both core and halo (-) emission from M31 disk Perez, Ng, Beacom+ (2017) Ng, Roach, Perez+ (2019) M31 (Andromeda Galaxy) (+) minimal Galactic contamination (+) near center of the dark matter halo (-) seeing deviations from instrument background model B. Roach, Ng, Perez+ (2020) Off-plane Galactic Center Leading sensitivity across broad mass range • Combination of Galactic center, Andromeda (M31), and Galactic bulge give leading constraints for masses 10-50 keV • Improve on previous constraints by over an order of magnitude in some mass ranges Kenny Ng Brandon Roach (GRAPPA) (graduate student) Cora Hersh (Haverford undergrad à MIT EAPS Ph.D.) See also: Foster et al. A deep search for decaying dark matter with XMM-Newton arXiv:2102.02207 (2021) 15 Stars as factories for axion-like particles (ALPs) • Axions introduced to explain why the strong interactions preserve the CP symmetry (Peccei-Quinn mechanism) • Axion-like particles generic feature of many BSM models (e.g. string theory) Couples to fermions Couples to photons Compton Bremsstrahlung Primakoff Most relevant process for stars! photon axion photon* Image: Hubble Telescope 17 Galactic magnetic fields photon photon axion NuSTAR photon* photon* Image: Hubble Telescope Jaffe (2019) 18 Betelgeuse 1. Hot core à predicted signal in the hard X-ray range 2. No stable corona à essentially zero standard astrophysical X-ray background 3. Relatively nearby, well- studied region Dr. Mengjiao Xiao (postdoc researcher) M. Xiao, Perez, See also: Dessert, Foster, Safdi Gianotti+ X-ray searches for Axions from Super Star Clusters, PRL (2021) PRL (2021) Image credit: Sky & Telescope Magazine 19 Astro observations constrain light axion-like particles predicted axion spectra data (background subtracted) Astro observations constrain light axion-like particles predicted axion spectra data (background subtracted) Xiao, Perez, Gianotti+ PRL (2021) • No excess of events over the expected background • Limits at least ~3x deeper than CAST • Comparable to next- generation axion experiments ALPS-II and Baby-IAXO Astro observations constrain light axion-like particles • overlapping astrophysical constraints, with separate modeling assumptions and uncertainties • builds confidence in the exclusion of this corner of parameter space Xiao, Perez, Gianotti+ PRL (2021) See also: Dessert, Foster, Safdi X-ray searches for Axions from Super Star Clusters, PRL (2021) Novel X-ray Optics for the International Axion Observatory • The International Axion Observatory (IAXO) is the successor to the current leading axion solar telescope, CAST • Axions from Sun re-converted to photons in large laboratory magnetic field • The X-ray optics assembly expands the technology developed for NuSTAR, XRISM, XMM-Newton, etc. 8 X-ray optics focus signal onto low- background detectors JCAP 1906 (2019) 047 arXiv:1904.09155 23 • NuSTAR has delivered leading sensitivity to light dark matter and stellar backgrounds to new physics • Much of this sensitivity not foreseen before launch! • Looking forward to other new windows opening on our sky Backup 25 …Elephants in the Galactic center? Measured MWD ~ 0.9MO is much heavier than implied by low-energy X-ray surveys Higher temperature, All looking at the same elephant…that weighs ~0.9M proportional to MWD O Measured by hard X-rays ...and different animals altogether in the Galactic bulge: cooling material, Perez, Krivonos, Wik ApJ (2020) peak emissivity <10 keV Measured by soft X-rays Hailey, Mori, Perez+ ApJ (2016) Hong+ ApJ (2016) – Point sources in central 100 pc 26 Population changes in the Galactic bulge NuSTAR field-of-view (Module A) NuSTAR field-of-view (Module B) ~6° INTEGRAL image in 17-60 keV overlaid with stellar mass density distribution Perez, Krivonos, Wik. ApJ (2020) • First broad-band X-ray Galactic observations of the Galactic bulge bulge confirm spectrum dominated by non-magnetic white Cosmic X-ray Background dwarf binaries • No hard X-ray emission >20 keV • Supports conclusions from Fe emission line measurements Xu et al. 2016; Yamauchi et al. 2016; Koyama 2018; Nobukawa et al. 2016 27 Origins of Central Hard X-ray Emission? • Massive Intermediate Polars (IPs) …but <MWD> ≈ 0.9MO? • Quiescent black hole low-mass X-ray binaries …but previously undiscovered large population (~600-1200)? must have very faint or long-recurrence outburst? • Millisecond pulsars with non-thermal high-energy spectrum …but previously undiscovered large population (~3000) ? • Bremsstrahlung and inverse Compton from Sgr A* particle outflows interacting with dense molecular material (Dogiel et al. 2015) … but no correlation with radio or radiation density models? K. Perez - MIT 28 Point Sources in the inner 100 pc • 70 hard (3-79 keV) X-ray point sources in a 0.6 deg2 region around Sgr A* with a total exposure of 1.7 Ms • 7 sources in the Sgr B2 field with 300 ks • Sensitive to ~4x1032 erg s-1 in 3-10 keV and ~8x1032 erg s-1 in 10-40 keV NuSTAR 10-40 keV Trial Map J. Hong+ (2016) arxiv:1605.03882 NuSTAR point sources indicate heavy mCVs • The NuSTAR (10-40 keV) J. Hong+ (2016) arxiv:1605.03882 and Chandra (0.5-8 keV) distributions match if the average spectra are Γ~1.5- 2 or kT ~ 20-50 keV • High percentage with Fe lines (60%) and hard spectra support dominant mCV population • High plasma temperature translates to MWD > 0.8MO • Consistent with average white dwarf mass measured by SDSS K. Perez - MIT 30 Adapting NuSTAR as a large-aperture DM telescope • “0-bounce” photons that bypass the optics are typically a major background 3.5 deg • Novel analysis exploits >10x increase in efficiency for slowly-varying, diffuse signal 0.2 0.4 0.6 0.8 31 Population changes in the Galactic bulge? Xu (2016); Yamauchi+ (2016); Yuasa et al.