[PPT] - The Fermi Large Area Telescope Science highlights and prospects PowerPoint Presentation

SLIDE 1

The Fermi Large Area Telescope

Science highlights and prospects for the extended mission Luca Baldini

Universit` a and INFN–Pisa luca.baldini@pi.infn.it

n behalf of the Fermi LAT

collaboration Astroparticle Physics 2014, Amsterdam June 25, 2014

SLIDE 2

Fermi at Astroparticle Physics 2014 (1/2)

Cast of characters (in strict alphabetical order)

◮ Markus Ackermann: “The intensity and origin of the isotropic

gamma-ray background” [24 Jun @ 16:30]

◮ Keith Bechtol: “Gamma-ray Observations of Galaxy Clusters and

Implications for Cosmic Rays” [23 Jun @ 16:30]

◮ Rolf Buehler: “Galactic particle accelerators” [25 Jun @ 11:00] ◮ Anna Franckowiak: “The Spectrum and Morphology of the Fermi

Bubbles” [25 Jun @ 17:00]

◮ Marie-Helene Grondin: “Gamma-ray observations of the pulsar wind

nebula 3C58 with the Fermi-LAT” [25 Jun @ 14:20]

◮ Lucas Guillemot: “Fermi LAT observations of gamma-ray pulsars”

[25 Jun @ 14:50]

◮ Marianne Lemoine-Goumard: “Constraints on Cosmic-Ray Origin

from Gamma-Ray observations of Supernova Remnants” [24 Jun @ 17:00]

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 2 / 25

SLIDE 3

Fermi at Astroparticle Physics 2014 (2/2)

Cast of characters (in strict alphabetical order)

◮ Melissa Pesce-Rollins: “Fermi Large Area Telescope observations of

high-energy gamma-ray emission from solar flares” [23 Jun @ 15:10]

◮ Gabrijela Zaharijas: “Recent results on dark matter search with the

Fermi LAT” [23 Jun @ 14:30]

◮ Stephan Zimmer: “Search for DM-induced gamma-rays from Galaxy

Clusters with the LAT” [23 Jun @ 14:55] And broader talks, e.g.,

◮ Valerie Connaughton: “Prospects for detecting Gamma-Ray Bursts

at the highest energies” [23 Jun @ 17:20]

◮ Luigi Tibaldo: “Galactic interstellar gamma-ray emission” [25 Jun @

15:30] And probably as many others by the Community analyzing Fermi data.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 3 / 25

SLIDE 4

Fermi: a remarkably large dynamic range

(Fermi LAT and GBM combined) Energy [MeV]

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Time [s]

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10 Binary systems Pulsar substr. AGN flares Pulsar periods Solar flares TGF GRB prompt GRB extended

Distance [m]

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10 TGF CRE Earth limb Galactic Moon AGN Sun GRB

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 4 / 25

SLIDE 5

Outline

For the next 20 minutes

◮ My three favorite.

◮ (Among the Fermi-LAT publications coming out in the short term.)

◮ Why, after 6 years in orbit, are we excited about the Fermi extended

mission?

◮ Time-domain astronomy; ◮ Pass 8. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 5 / 25

SLIDE 6

The IGRB and EGB

Earlier talks by Markus Ackermann and Gabrijela Zaharijas

◮ Updated LAT measurement of IGRB spectrum.

◮ 50 months of data, dedicated event selection(s). ◮ Extended energy range: 200 MeV–100 GeV → 100 MeV–820 GeV.

◮ Roughly ∼ 1/2 of total EGB intensity above 100 GeV now resolved

into individual sources.

◮ Significant high-energy cutoff feature around ∼ 250 GeV.

◮ Consistent with simple source populations attenuated by EBL. ◮ Reality might more complex, with multiple populations contributing. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 6 / 25

SLIDE 7

The Fermi bubbles

Talk by Anna Franckowiak later today—can’t miss that!

◮ First discovered by Su, Finkbeiner & Slatyer in 2010. ◮ First Fermi-LAT publication.

◮ Based on 50 months of data. ◮ Modeling of the diffuse emission is the foremost challenge.

◮ Hard spectrum with cutoff at ∼ 110 GeV.

◮ No spectral variations in latitude stripes. ◮ No energy dependence of the overall morphology. ◮ Excess emission in the the South-East; no evidence for a jet.

◮ Leptonic and hadronic interpretation of gamma-ray data possible.

◮ Assuming association with microwave haze prefers leptonic models. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 7 / 25

SLIDE 8

The 3FGL

Heading toward ∼ 3000 sources

◮ 4 years of Pass 7 reprocessed LAT data above 100 MeV:

◮ vs. 2 years of (un-reprocessed) Pass 7 data for the 2FGL. ◮ Front/Back handled separately (different isotropic and Earth limb).

◮ More data and improved performance (due to reprocessing):

◮ Better localization on average (error radius ∼ 15% smaller outside

the Galactic plane).

◮ Improved interstellar model of Galactic diffuse (e.g., Fermi bubbles):

◮ Lower overall detection threshold.

◮ Association process improved.

◮ Dedicated multiwavelength follow-up, new surveys. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 8 / 25

SLIDE 9

Fermi and the Galactic center

◮ A topic of discussion that stirred the interested of the community

ver the last few months.

◮ The Fermi-LAT collaboration is fully engaged in studying the sources

f gamma-ray emission in the inner Galaxy:

◮ Modeling of the Galactic diffuse emission is (again) the foremost

challenge.

◮ “Diffuse emission around the Galactic center” is one of the top three

for the next few years in L. Tibaldo’s review on GDE this afternoon.

◮ Fermi transitioned to a new observing profile emphasizing coverage

f the Galactic center (more on this later).

◮ Dedicated session on the “Galactic center GeV excess” tomorrow

afternoon.

◮ Including presentations and ∼ 1/2 hour of panel discussion. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 9 / 25

SLIDE 10

Extended mission and timeline

Year

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 # orbits 10000 20000 30000 Distance traveled [km] 500 1000

6

10 × # triggers 50 100 150 200 250 300 350

9

10 × # events downlinked 10 20 30 40 50 60 70

9

10 × # events @ FSSC 500 1000 1500 2000

6

10 ×

ray candidates

γ # 50 100 150 200 250 300

6

10 ×

2 5 5 7 5 1 1 2 5 1 5 1 7 5 2 2 2 5 2 5 2 7 5

# ATELs

1 2 3 4 5 6 7 8

# GCNs

Prime phase Extended phase

SR 2012 SR 2014

Full SR reports @ http://science.nasa.gov/astrophysics/documents/

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 10 / 25

SLIDE 11

Faster than the √t: time-domain astronomy

◮ Laundry list of source classes:

◮ GRB, AGN, Solar Flares, TGFs, novae. . .

◮ Large acceptance and FOV, all-sky coverage and long integration

time are key.

◮ Fermi surely plays a prominent role—in synergy with other

instruments and observatories.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 11 / 25

SLIDE 12

GRB 130427A

A nearby monster!

◮ Highest γ-ray fluence: ◮ Highest γ-ray energy in the

LAT frame:

◮ 95 GeV @ T0 + 244 s; ◮ 32 GeV @ T0 + 34.4 ks;

◮ Longest-lived γ-ray emission:

◮ 19 hours.

◮ Second brightest optical flash:

◮ 7-th magnitude.

◮ Within closest 5% of GRBs:

◮ z = 0.34.

◮ A rapid localization by the

Fermi LAT and GBM is crucial to enable this kind of science.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 12 / 25

SLIDE 13

Faster than the √t: steady sources

—Low energy

Bkg. dominated

∝ √t —High energy Photon counting nearly ∝ t

◮ Envelope of the minimum detectable power-law spectra over the full

band, varying the spectral index.

◮ (i.e, not a differential sensitivity plot.)

◮ High-energy limiting sensitivity comes from photon counting

statistics (rather than the background).

◮ Increase nearly linear with time, rather than √t. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 13 / 25

SLIDE 14

Faster than the √t: external inputs

◮ Specific LAT analyses rely on external inputs.

◮ And our knowledge of these inputs advances independently.

◮ Galactic diffuse model and Planck maps.

◮ This impacts (to different extents) pretty much all the analyses of

Fermi data.

◮ Radio timing solutions for pulsar searches.

◮ The rate of discovery for pulsars has been ∼ constant through the

prime phase of the mission.

◮ Note this goes in the other direction, too: searches for radio

pulsation in LAT unassociated sources.

◮ Targets for indirect DM searches.

◮ e.g., dwarf spheroidal galaxies. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 14 / 25

SLIDE 15

The role of the observing strategy

◮ Two basic observation modes:

◮ Survey mode: tilt z-axis perpendicular to orbit plane (±50◦). ◮ Pointing mode: point z-axis to a specific location in the sky. ◮ Nearly all pointed observations interrupted by Earth occultation.

◮ Survey mode provides ∼ uniform sky exposure. ◮ Coverage of specific parts of the sky can be enhanced by pointed

bservations.

◮ ARRs and TOOs (e.g., PSR B1259-63, 3C279, the Crab, the Sun. . . )

◮ Fermi transitioned to a new default observing mode with emphasis

n the GC in December 2013.

◮ Community actively involved in the decision. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 15 / 25

SLIDE 16

Long-baseline measurements

◮ Binary system PSR B1259-63: a radio pulsar in a highly-eccentric

rbit (period 3.4 years) around a main sequence star.

◮ Large increase of the flux at GeV energies one month after the last

periastron passage in 2011.

◮ No corresponding variability observed in radio, X-rays and VHE γ.

◮ Current periastron passage on May 4, 2014.

◮ Recurrent nature of the flaring activity seems to be confirmed. ◮ 6 ATELs over the last three weeks. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 16 / 25

SLIDE 17

Pass 8

Cover image: a 540 GeV simulated gamma ray

x z

◮ Long-term effort aimed at a comprehensive revision of the entire

LAT event-level analysis.

◮ Simulation, reconstruction, background rejection, analysis methods. ◮ Incorporating the experience of the prime phase of the mission.

◮ Goals: extending the energy reach, maximizing the S/N, reducing

the systematic uncertainties.

◮ Basic analysis components ready, now entering science validation.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 17 / 25

SLIDE 18

IRFs: Pass 8 vs. Pass 7

Note this is Monte Carlo based

Energy [MeV] sr]

2

Acceptance [m

0.5 1 1.5 2 2.5 3

P8_SOURCE prototype P7REP_SOURCE_V15

P r e l i m i n a r y Energy [MeV]

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Ratio (P8/P7)

1 10

Energy [MeV] ] ° Containment angle [

1

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P7REP_SOURCE_V15 (on-axis 95%) P8_SOURCE prototype (on-axis 95%) P7REP_SOURCE_V15 (on-axis 68%) P8_SOURCE prototype (on-axis 68%)

P r e l i m i n a r y Energy [MeV]

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Ratio (P7/P8)

0.5 1 1.5 2

◮ Larger acceptance at all energies.

◮ Most notably below 100 MeV (×2 at 100 MeV and ×10 at 30 MeV) ◮ Performing spectral analysis down to such low energies presents

significant challenges (e.g., energy dispersion).

◮ Larger field of view.

◮ More off-axis effective area.

◮ Narrower PSF at moderate-to-high energies, with reduced tails.

◮ Can improve PSF further by tightening event selections. ◮ Preliminary indications that an in-flight correction is not needed.

◮ Comparable energy dispersion.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 18 / 25

SLIDE 19

Pass 8: source sensitivity

Energy [MeV] ]

1

s

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dN/dE [erg cm ×

2

E

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P8_SOURCE prototype P7REP_SOURCE_V15 25 with at least 10 counts per bin) ≥ (4 years, TS Point source sensitivity at mid-Galactic latitude

P r e l i m i n a r y Energy [MeV]

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Ratio (P7/P8)

0.8 1 1.2 1.4 1.6 ◮ Combination of larger acceptance and better PSF at high energy. ◮ 20–50% increase in sensitivity for a given observing time.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 19 / 25

SLIDE 20

Pass 8 science return: high energy

Redshift

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Energy [GeV]

10

2

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BLLacs FSRQs GRBs (Pass 6 and Pass 8) GRBs (new in Pass 8) for various EBL models = 1) τ Predicted optical depth (

◮ ∼ 20% acceptance increase at high energy.

◮ And relatively (much) larger at large off-axis angles.

◮ Re-analysis of the prompt phase of GRBs with measured redshift in

the first LAT GRB catalog.

◮ Really testing the new event reconstruction.

◮ 4 photons above 10 GeV (previously discarded) recovered in Pass 8.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 20 / 25

SLIDE 21

Pass 8 science return: low energy

Counts/bin

200 250 300 350 400 450

Crab (30-60 MeV)

P8_SOURCE prototype = 23480, H = 6097

source

n

Preliminary Pulse phase Counts/bin

50 100 150 200 250

P7REP_SOURCE_V15 = 4049, H = 1489

source

n

Pulse phase Counts/bin

200 300 400 500 600 700 800

Crab (60-100 MeV)

P8_SOURCE prototype = 27941, H = 18444

source

n

P r e l i m i n a r y Pulse phase

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Counts/bin

100 200 300 400 500 600

P7REP_SOURCE_V15 = 8961, H = 6307

source

n

Counts/bin

145 150 155 160 165 170

J1513-5908 (30-60 MeV)

P8_SOURCE prototype = 3789, H = 77

source

n

Preliminary Pulse phase Counts/bin

25 30 35 40 45 50

P7REP_SOURCE_V15 = 818, H = 10

source

n

Pulse phase Counts/bin

90 95 100 105 110 115

J1513-5908 (60-100 MeV)

P8_SOURCE prototype = 2445, H = 101

source

n

P r e l i m i n a r y Pulse phase

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Counts/bin

35 40 45 50 55 60

P7REP_SOURCE_V15 = 1030, H = 50

source

n

◮ Background-subtracted pulse profiles for the Crab and J1513-5908

pulsars (2 years of data, 15◦ ROI) below 100 MeV.

◮ Large increase in the counting statistics. ◮ Large increase in H-test significance—exciting for faint pulsars.

◮ Substantially improved sensitivity for time-domain astronomy.

◮ Blind and epoch-folding pulsar searches. ◮ Transient searches (novae, blazar flares, etc.). Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 21 / 25

SLIDE 22

Looking again at the acceptance

Energy [MeV] sr]

2

Acceptance [m

0.5 1 1.5 2 2.5 3

P8_SOURCE prototype P7REP_SOURCE_V15

P r e l i m i n a r y Energy [MeV]

2

10

3

10

4

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5

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Ratio (P8/P7)

1 10

Flight data (Crab)

◮ Note the addition of the square data points in the bottom panel.

◮ Derived from the Crab pulse profiles in the previous slide.

◮ Increase in the total number of events is consistent with Monte

Carlo predictions.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 22 / 25

SLIDE 23

(More) Pass 8 in action

Counts/bin

5 10 15

(30-60 MeV) GRB100826A Preliminary

P8_TRANSIENT prototype = 81

evts

n P7REP_TRANSIENT_V15 = 16

evts

n

Time since trigger [s]

300
200
100

100 200 300

Counts/bin

1 2 3 4 5

(60-100 MeV) GRB100826A Preliminary

P8_TRANSIENT prototype = 18

evts

n P7REP_TRANSIENT_V15 = 9

evts

n

◮ Relatively faint GRB, 73◦ off-axis.

◮ This GRB was an LLE1-only detection in the first LAT GRB catalog.

◮ Clear detection in the standard event classes with Pass 8.

1LAT Low-Energy analysis.

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 23 / 25

SLIDE 24

(More) Pass 8 in action

◮ Substantial difference between LLE and standard likelihood source

analysis: you get a localization!

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 24 / 25

SLIDE 25

Conclusions

◮ Six years into the mission, the Fermi Gamma-ray Space Telescope

continues providing a broad range of scientific results.

◮ LAT science extensively covered in this conference. ◮ Large community interested in the analys of LAT data. ◮ (Thanks! This is extremely important for keeping us flying.)

◮ More results coming out in the near future. ◮ And we are very excited for the rest of the extended phase of the

mission. And now something completely different: the Fifth International Fermi Symposium will take place in Nagoya, Japan, on October 20–24, 2014. http://fermi.gsfc.nasa.gov/science/mtgs/symposia/2014/

Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 25 / 25