Exploring the Universe: (Some of) The Latest Results from Fermi-LAT

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Exploring the Universe:

(Some of) The Latest

Results

from Fermi-LAT

Peter Michelson

Spokesperson, Fermi LAT Collaboration

Stanford University [email protected]

AMS Days at CERN

April 16, 2015 AMS Days at

CERN

April 16, 2015

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Electromagnetic Observations of Space

gamma-ray2

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To understand the Universe and its origin and evolution we need data from across the

electromagnetic spectrum, cosmic rays measured with very high precision, and eventually from new channels (ie., gravitational radiation)

In particular, at this meeting,

“The accuracy and characteristics of data,

simultaneously from many different types of cosmic- rays, require a comprehensive model to ascertain if their origin is from dark matter, astrophysical

sources, acceleration mechanisms or a combination”

Professor Samuel Ting

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• Fermi LAT instrument: A brief overview and

important updates (Pass 8) to event reconstruction and instrument performance

• The gamma-ray sky: updates to LAT source catalogs (3FGL)

• Indirect search for Dark matter

• An update on a few important source classes in the cosmic zoo of high-energy gamma-ray sources

• Pulsars

• gamma-ray bursts

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Large Area Telescope (LAT): 20 MeV to more than 300 GeV;

observes 20% of the sky at any instant, entire sky every 3 hrs

Gamma-ray Burst Monitor (GBM):

8 keV to 40 MeV

observes entire unocculted sky

International and interagency

collaboration between NASA and DOE in the US and agencies in

France (CEA, CNRS-IN2P3), Germany (MPE, DLR),

Italy (ASI, INFN), Japan (JAXA), Sweden (KTH

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Fermi Observatory

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Fermi LAT Collaboration

 France

 IN2P3, CEA/Saclay

 Italy

 INFN, ASI, INAF

 Japan

 Hiroshima University

 ISAS/JAXA

 RIKEN

 Tokyo Institute of Technology

 Sweden

 Royal Institute of Technology (KTH)

 Stockholm University

 United States

 Stanford University (SLAC, KIPAC, and HEPL/Physics)

 University of California at Santa Cruz - Santa Cruz Institute for Particle Physics

 Goddard Space Flight Center

 Naval Research Laboratory

 Sonoma State University

 Ohio State University

 University of Washington LAT construction and operation

managed by

SLAC National Accelerator Laboratory, Stanford University

Sponsoring Agencies Department of Energy

National Aeronautics and Space Administration CEA/Saclay ASI

IN2P3/CNRS INFN

MEXT K. A. Wallenberg Foundation KEK Swedish Research Council JAXA Swedish National Space Board

also members from Australia, Germany, Great Britain, Spain, South Africa,

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LAT Collaboration science analysis led by group coordinators

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Science Group Current coordinators Calibration & Analysis Carmelo Sgrò

Matthew Wood Dark Matter & New

Physics

Andrea Albert

Miguel A. Sánchez-Conde

Diffuse Anna Franckiowiak

Gudlauger Johannesson

Catalog Jean Ballet

Elisabetta Cavazzuti Isabelle Grenier

Solar System Eric Grove

Francesco Longo

AGN Jeremy Perkins

Dario Gasparrini Galactic Sources John Hewitt

Massimiliano Razzano GRB (LAT members) Elisabetta Bissaldi

Magnus Axelsson

the broad expertise across collaboration is important for complex analysis and interpretation.

Analysis Coordinator: Philippe Bruel -> Luca Baldini Deputy AC: Luca Baldini -> Jeremy Perkins

Coordinators – March 2015 Tyrel Johnson

Matthew Wood Andrea Albert

Miguel A. Sánchez-Conde Anna Franckiowiak

Gudlauger Johannesson Jean Ballet

Elisabetta Cavazutti Isabelle Grenier Francesco Loparco Francesco Longo Roopesh Ojha Dario Gasparini John Hewitt

Massimiliano Razzano Nicola Omodei

Magnus Axelsson

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LAT images the sky one photon at a time: -ray converts in LAT to an electron and a positron ; direction and energy of these particles tell us the direction and energy of the photon

GBM

Large Area Telescope (LAT)

403 billion triggers; 81 billion downlinked events 2.6 billion “transient” events available at FSSC 429 million source photons at FSSC

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LAT data used for many types of analyses

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Solar Flare/ GRBs Solar Flare/ GRBs TGFsTGFs

Point Sources Point Sources Galactic Diffuse Galactic Diffuse

Isotropic Diffuse & Dark Matter

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Pass 8: LAT performance improvements

30 GeV event

improved instrument simulation; major rework of event reconstruction; new event selection and event classes validation complete; release this month (April 2015);

followed by upgraded analysis package in ~6 months

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Pass 8: LAT performance improvements

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better acceptance and sensitivity at low and very high energy energies

Extended energy measurement range: from ~10 MeV to

~ 3TeV

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Pass 8: Crab Pulsar light curves

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Pass 8: Multiple event types

Event classes subdivided to make more optimal use of event information

• data split into 4 event types; with increasing PSF/energy resolution quality

• using the PSF event types in a joint likelihood analysis

provides additional ~10% improvement in source sensitivity

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70% of the photons in the high-energy -ray sky are diffuse radiation

from the Milky Way; The remainder are localized sources or extragalactic

“diffuse” radiation

The Fermi sky above 1 GeV

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The restless Universe

36 months E > 100 MeV

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many transients in the -ray sky with time, deeper exposure has

revealed many new sources and new source

classes

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Dark Matter searches

Terrestrial γ-ray Flashes

Fermi Highlights and Discoveries Fermi Highlights and Discoveries

GRBs

Fermi Bubbles

Novae SNRs &

PWN

Blazar Radio s

Galaxies

LMC &

SMC Starburst

Galaxies

γ-ray Binaries Globular

Clusters

Sun: flares & CR interactions

Pulsars: isolated, binaries, &

MSPs

Unidentified Sources

Galactic

Extragalactic

e⁺e^- spectrum

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2^nd Fermi LAT Source Catalog

1,873 sources

ApJS 199, id. 31 (2012)

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3^nd Fermi LAT Catalog

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1873 source s

1451 source s

3033 source s

arXiv:1501.02003

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3FGL Source Catalog

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3FGL Source Classes

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Largest identified or associated source class is Active Galaxies

• 1,563 of 2,192 3FGL high-latitude sources (b >

10^o) are AGNs; 98% are blazars

red: FSRQs, blue: BL Lacs,

magenta: radio galaxies, green: unknown type

Redshft distribution (dashed are new sources not in 2LAC)

3LAC: Third LAT Catalog of AGNs arXiv: 1501.06054

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1FHL: 1^st Fermi LAT Catalog of Sources above 10 GeV

Ap J Suppl 209,34 (2013) 514 sources

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1FHL: 1^st Fermi LAT Catalog of Sources above 10 GeV

10% of sources with no 2FGL associations

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Pass 8: 2FHL Source Catalog in preparation

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significant improvement in LAT performance > 50 GeV

improvement in PSF and acceptance between 20% and 100%

PSF ~ 0.1 deg @ 68%

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Pass 8: 2FHL Catalog

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51,000 photons above 50 GeV

6 years of data

~ 350 sources above 50 GeV

(vs 238 in 1FHL)

Survey of sources > 50 GeV connects well to ICATs, HAWC and CTA

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GRBs

Fermi Bubbles

Novae SNRs &

PWN

Blazar Radio s

Galaxies

LMC &

SMC Starburst

Galaxies

Clusters

MSPs

Galactic

Extragalactic

e⁺e^- spectrum

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Dark Matter Searches with Fermi

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Searches for annihilation radiation from Weakly

Interacting

Massive Particles involve a

number of targets.

dwarf spheroidal galaxies, unidentified satellites, galaxy clusters

low background but low statistics

Galactic center, Milky Way halo, isotropic gamma-ray background

large statistics but large backgrounds/foregrounds

and a possible smoking gun – annihilation line(s)

but suppressed in most scenarios

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2015: An interesting start

LAT Collaboration – DES Collaboration agreement – Feb 2015

- first joint paper “Search for Gamma- Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data”

arXiv:1503.02632

• analysis of observations of 8 new Dwarf Spheroidal Galaxies found by DES:

Bechtol, et al.

arXiv:1503.02584 also found by

Koposov, et al.

arXiv:150302079

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DES Candidate Dwarf Spheroidal Galaxies

DES Collaboration provided coordinates of their new candidate Dwarf Galaxies

Thanks to well-developed analysis pipeline and a group of very dynamic people, LAT and DES posted and submitted analysis for gamma-ray emission from these objects on March 9

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DES Dwarf Spheroidal Candidates

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arXiv:1503.02632

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Galactic Center region

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GRBs

Fermi Bubbles

Novae SNRs &

PWN

Blazar Radio s

Galaxies

LMC &

SMC Starburst

Galaxies

Clusters

MSPs

Galactic

Extragalactic

e⁺e^- spectrum

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Fermi Pulsars

161 gamma-ray pulsars

announced (more on the way!)

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Fermi Pulsars: A surprising harvest of MSPs

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15 7

17

2009

gamma only MSP

radio + gamma

2014

41 69

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Growing fraction of

millisecond pulsars: 43% at present

(Note: bias against finding MSPs in blind searches)

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Radio MSP searches

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discovery rate is constant

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Fermi Pulsars

L_ ^

L_  ^

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PSR J0540-6919: first extragalactic gamma-ray pulsar

twin of Crab pulsar with large spin- down power

- and probably the highest L_.

Phase- averaged spectrum (75 months)

Preliminary

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> 200 Gamma-ray Pulsars*

* includes radio pulsars found by PSC in Fermi unID sources

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Pass 8: 10 new LAT Pulsars (so far)

• 5 young pulsars

• PSR

J1856+0113

• PSR

J1857+0143

• PSR J1831-0952

• PSR J1837-0604

• PSR J1224-6407

• 4 MSPs

• PSR J0742+6620

• PSR J1455-3330

• PSR J1730-2304

• PSR J0931-1902

PSR

J1856+0113, central object of SNR W44;

both detected in gamma-rays

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GRBs

Fermi Bubbles

Novae SNRs &

PWN

Blazar Radio s

Galaxies

LMC &

SMC Starburst

Galaxies

Clusters

MSPs

Galactic

Extragalactic

e⁺e^- spectrum

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GRBs: The Birth Announcement of Black Holes(?)

• first Detected in late 1960's

• declassified in early 1970's

• shown to have an isotropic distribution on the sky 1990's (BATSE)

• proven to be extragalactic late 1990's (Beppo-Sax)

Two Distinct Populations: Long & Short

Collapsar Model

MacFadyen & Woosley

Long GRBs: Stellar Collapse Short GRBs: NS-NS Mergers?

Simulations: Price & Rosswog (2006)

some associated with Supernovae 46

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Fermi GRBs

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GBM detects ~240 bursts/yr 19% are short

LAT detects ~9.5 -> 15 bursts/yr 7/79 (9%) are short

New algorithm; expect further improvement with Pass 8

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Fermi GRBs: long vs short bursts

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LAT/GBM fluence ratio larger for short GRBs relative to long GRBs

short GRBs are spectrally harder

LAT HE emission delayed relative to low energy emission; delay scales with GRB duration

Constraints on bulk 

observed high-energy cutoff from intrinsic pair production, then  ~ 200 - 700

Abdo et al. 2009, Science, 323, 1688

GRB 090510

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GRBs and Pass 8

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5σ threshold 5σ threshold

G. Vianello: 100 GRB simulated on true bkgrd; transient class events

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GRBs

Fermi Bubbles

Novae SNRs &

PWN

Blazar Radio s

Galaxies

LMC &

SMC Starburst

Galaxies

Clusters

MSPs

Galactic

Extragalactic

e⁺e^- spectrum

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To understand the Universe and its origin and evolution we need data from across the

electromagnetic spectrum, cosmic rays measured with very high precision, and eventually from new channels (ie., gravitational radiation)

In particular, at this meeting,

“The accuracy and characteristics of data,

simultaneously from many different types of cosmic- rays, require a comprehensive model to ascertain if their origin is from dark matter, astrophysical

sources, acceleration mechanisms or a combination”

Professor Samuel Ting

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Backup

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Reticulum II: DES-LAT versus Geringer-Sameth et al. analysis

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The largest deviation found by DES-LAT is for J0335.6-5403, corresponding to a local

significance of 2.3sig.

• significance calibration using random ROIs

• taking account of masses &

channels trials -> 1.5sig

Geringer-Sameth, et al., find local significance of 3.7sig

• reduced to 2.3sig when using random ROIs

DES-LAT use Pass 8

Geringer-Sameth, et al. use Pass 7, no event types

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Dwarf Galaxies vs Globular Clusters

from A. Drlica-Wagner, K. Bechtol and DES Milky Way Working Group: arXiv: 1503.02584

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Isotropic Gamma-Ray Background

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1873 source s

1451 source s

3033 source s

(IGRB + resolved high latitude sources)

Ackermann, et al. (2014) arXiv:1410.3696

Spectrum: power law plus exponential cutoff

spectral index ~ 2.3 cutoff energy ~350 GeV shape of cutoff compatible with

absorption of gamma-rays in the extragalactic background light.

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Fermi-LAT observations of nearby galaxies

SMCSMC

LMCLMC 30 Dor

30 Dor

M 81 Andromeda M 81 Andromeda