TeV γ-ray astronomy and the project ASTRI*/CTA - sif.it · TeV γ-ray astronomy and the project...

TeV γ-ray astronomy and

the project ASTRI*/CTA

Nicola La Palombara (INAF – IASF Milano)

on behalf of the ASTRI Collaboration

XCIX Congresso Nazionale della Società Italiana di Fisica – Trieste – 23-27 September 2013

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The VHE γ–ray sky

The ASTRI Project

N. La Palombara –XCIX Congresso Nazionale della Società Italiana di Fisica –Trieste – 23-27 Settembre 2013

> 150 sources 50 extragalactic

© TeVcat (May 2012)

2/28

From the current generation of IACTs…

The ASTRI Project

HESS (4 x 12 m + 1 x 28 m) MAGIC (2 x 17 m)

CANGAROO (4 x 10 m) VERITAS (4 x 12 m)

N. La Palombara –XCIX Congresso Nazionale della Società Italiana di Fisica –Trieste – 23-27 Settembre 2013 3/28

…to CTA: a worldwide challenge…

The ASTRI Project


…for a new observatory for VHE γ–ray astrophysics

The ASTRI Project

CTA goals:

• increase the sensitivity by up to a factor 10 @ 1 TeV

• boost the detection area for transient phenomena and at the highest energies

• increase the angular resolution while maintaining a large field of view

• provide uniform energy coverage from a few tens of GeV to beyond 100 TeV

• enhance the sky-survey capability, monitoring capability and flexibility of operations

thanks to 2-sites (North & South), sub-array and simultaneous multi-mode runs

• operation as an “open” Observatory: peer-reviewed process on submitted proposals

CTA concept (Hofmann & Martinez, 2011, Exp. Astr., 32): array of several tens of

telescopes divided in 3 kinds of configurations, in order to maximize the telescope

performance in 3 different energy ranges.


CTA will continue the discovery trend

The ASTRI Project


CTA as a priority for the European Union

The ASTRI Project

CTA Project considered as a priority in

roadmaps of:

• ASTRONET (Astrophysics)

• ASPERA (Astroparticles)

• ESFRI (European Strategic Forum

for Research Infrastructures)

Project Construction

cost [M€]

Operations

cost [M€] Timescale

CTA 150 10 2013

E-ELT 950 30 2018

ELI 400 50 2015

FAIR 1187 120 2016

KM3NeT 200 5 2016

PRINS 1400 300 2009-2015

SKA (GLOBAL) 1500 100-150 2016

SPIRAL2 196 6.6 2014


The ASTRI Project

CTA candidate sites


The ASTRI Project


CTA and the ASTRI Program

The ASTRI Project

Few Large Size Telescopes

for the low energy range:

E ≃ 20 GeV – 1 TeV

~ 25 MSTs ~ 70 SST

4 LSTs

~ 1 km2 array of Medium Size

Telescopes for the core energy

range: E ≃ 0.1 – 10 TeV

Large array of Small Size

Telescopes for the high

energy range: E > 1 TeV

Within this framework, ASTRI aims to realize an end-to-end prototype for the SST


The ASTRI Project

The ASTRI SST-2M Prototype Program

ASTRI: Astrofisica con Specchi a Tecnologia Replicante Italiana

An Italian “Progetto Bandiera” (Flagship Project)

• funded by the Ministry of Education, University and Research (MIUR)

• led by the Italian National Institute of Astrophysics (INAF)

Aim: development of the “replica” technology for mirrors and new

sensors for VHE astrophysics.

Main goal: realization and test, within the framework of the Cherenkov

Telescope Array (CTA), of an end-to-end prototype of the CTA SST

INAF tasks: design and manufacturing of the mirrors and the camera;

development of the software and other related activities; scientific

supervision of the design of the telescope structure; acquisition and analysis

of the prototype data for the technological and scientific verification


The ASTRI Project

The ASTRI Collaboration

Principal Investigator: G. Pareschi

Co-PIs: O. Catalano

S. Vercellone

INAF Institutions

IASF Milano

IASF Bologna

IASF Palermo

OA Brera

OA Padova

OA Torino

OA Bologna

OA Arcetri

OA Roma

OA Capodimonte

OA Catania

INAF HQ Roma

University Partners

University of Padova

University of Perugia


The ASTRI Project

ASTRI SST-2M concept:

a large (9.6o) field of view dual-mirror

(Schwarzschild-Couder) telescope

a light (~ 50 kg) and compact (~ 56 x 56 x 56

cm3) camera based on Hamamatsu Si-PMs, with

a low power consumption

The Dual Mirror SST

(SST-2M) Concept Canestrari

et al. 2013


The ASTRI SST-2M Optical design

The ASTRI Project

Schwarzschild-Couder configuration

Angular dependence of D80: the amount of

energy contained within 2x2 physical pixels

(6.2 mm logical pixel) is not less than 80 %

along the entire field of view


The ASTRI Prototype Mirrors

The ASTRI Project

Main characteristics of the mirrors:

• Primary Mirror diameter: 4.3 m (segmented)

• Secondary Mirror diameter: 1.8 m (monolithic)

• F#: 0.5

• Equivalent focal length: 2150 mm

• Corrected FoV diameter: 9.6o

Primary mirror segment

• off-axis aspherical profile obtained

with the glass Cold-Shaping

technology at INAF – OA Brera

• physical Vapor Deposition of a

multilayer of pure dielectric materials


The ASTRI Prototype Mirrors

The ASTRI Project

Secondary mirror (M2)

• Monolithic

• 3 actuators: tip-tilt and piston for alignment

and focusing purposes

Primary mirror (M1)

• 18 hexagonal shaped mirrors (11.2 m2)

• 850 mm face-to-face, 1 m diagonal

• 3 types of segments

• 2 actuators + 1 fixed point: tip-tilt

corrections for alignment purposes


The ASTRI Prototype Camera

The ASTRI Project

Requirement on the pixel size:

SC optical design

compact (~ 50 cm) camera

(small detection surface)

spatial segmentation of a few square millimeters

(to be compliant with the imaging resolving angular size)

Other requirements:

• photon detection sensitivity in the 300-700 nm range

• fast temporal response



The ASTRI Project

Main characteristics:

• Detector type: monolithic array of

4 x 4 Si Photomultipliers (SiPM)

provided by Hamamatsu

• Physical pixel: array of 60 x 60

elementary diodes of 50 μm pitch

• Physical Pixel size: 3 x 3 mm2

• Logical Pixel size: 6.2 x 6.2 mm2

[0.17o]

• Plate scale: 37.5 mm/o

• Number of Pixels: 7936

• Number of channels: 1984

(grouping 2 x 2 pixels)


The ASTRI Project

1 SiPM unit

4x4 physical pixels

2x2 logical pixels

1 Photon Detection

Module (PDM)

4x4 Units

1 Focal Surface Camera

37 PDMs

FoV diameter = 9.6o

A modular approach



The ASTRI Prototype Site

The ASTRI Project

• Altitude: 1735 m a.s.l.

• Longitude: +14o 58’ 04’’

• Latitude: +37o 41’ 05’’

ASTRI SST-2M Prototype

61cm Dome

91cm Dome

Domes

Guests House, Offices

and Laboratories

Main entrance

"M. G. Fracastoro" Mountain Station at Serra La Nave, on Mt. Etna:

observing site of the INAF Catania Astrophysical Observatory


The ASTRI Prototype Site

The ASTRI Project

"M. G. Fracastoro" Mountain Station at Serra La Nave, on Mt. Etna:

observing site of the INAF Catania Astrophysical Observatory

• Fully operative INAF Observatory

• High-speed internet connection

• Mechanical & Electronics Labs

• Area protected from wind and fallout of volcanic ash

• Medium seismicity risk but no earth faults ⇒ reduced earthquake risk

• Atmosphere transparency and relative humidity: values well inside the

limits required to perform Cherenkov observations

• Fraction of useful nights: > 53 %

• Length of “dark nights”: from ~ 6 h (in July) up to > 11 h (in January)

the ASTRI SST-2M prototype shall start data acquisition within 2014


The ASTRI Prototype Science

The ASTRI Project

The ASTRI Prototype is mainly a technological demonstrator, but science might be

feasible.

Maximum sensitivity for E > 2 TeV (1 Crab @ 5 s.d. in some hours)

In the range E > 10 TeV : 1 Crab @ 5 s.d. in a few tens of hours

First Crab observations with a Schwarzschild-Couder-SiPM Cherenkov telescope.

Possible sources (from Sicily): Crab, Mkn 421, Mkn 501

Intense flares (~ 5-10 Crab) should allow intra-night variability studies.

Bigongiari et al. 2013

Expected differential

rate for the Crab Nebula

Expected

prototype

sensitivity

Vercellone et al. 2013


The Mini-array Concept

The ASTRI Project

The ASTRI Collaboration has proposed also the realization of a mini-

array consisting of 5-7 SST-2M telescopes, to be installed at the final

CTA southern site and operated since 2016.


The Mini-array Goals

The ASTRI Project

The SST-2M mini-array will:

• verify array performance in terms of reliability and cost at the chosen

site

• check the trigger algorithms

• check the wide field-of-view performance, to detect very high energy

showers with the core located at a distance up to 500 m

• check the HW/SW configurations for the array

• check the data-handling chain

• compare the mini-array performance with the MC expectations by

means of deep observations of few selected targets

• validate the performance predictions for the full SST array (need well

chosen target objects and long observations)

• do the first CTA science, with its first solid detections during the first

year of operations


The ASTRI Project

The ASTRI Mini-Array

Control SW

Both the ASTRI end-to-end prototype

and the mini-array shall be operated

using the Mini-Array Software

System (MASS): set of tools to

perform all the steps of a scientific

observation (proposal preparation,

observation execution, data retrieving,

reduction and analysis)

System based on the ALMA Common

Software (ACS) framework

Compliant with the CTA Data

Management (CTA-DM) and CTA

Data Acquisition and Array Control

(CTA-ACTL)

Tosti et al. 2013


The ASTRI Project

The Mini-array Performance

Energy resolution: ~ 10-15 %

Limiting flux: ~ 10-12 erg/cm2/s @ 10 TeV

Angular resolution: ~ a few arcmin

Bigongiari et al. 2013

Di Pierro et al. 2013 Di Pierro et al. 2013

Di Pierro et al. 2013


The ASTRI Project

The Mini-array Primary Targets (south)

Galactic sources:

• Pulsar Wind Nebulae: Crab Nebula, Vela X, HESS 1825-137

• SNRs: Vela Junior, RX J1713.7-3946 / HESS J1718, Kepler

• SNRs interacting with MCs: W 28, W 30, W 51C, IC 443

• Microquasars: LS 5039

• The Galactic Centre (central source + diffuse emission)

Extragalactic sources:

• Extreme blazars: PKS 2155-304, 1ES 0229+200

• Nearby and intense BL Lac objects: MKN 421, MKN 501, (M 87)

PSF and Spectral Calibration

Weak source detection

Point-like and extended objects

Electron acceleration+cooling

Relativistic + non-relativistic shocks

Search for CR Pevatrons

CR propagation

FIR EBL

… N. La Palombara –XCIX Congresso Nazionale della Società Italiana di Fisica –Trieste – 23-27 Settembre 2013 27/28

Summary

The ASTRI Project

We plan to start the activities of the ASTRI SST-2M Prototype at Serra La

Nave at the end of 2014.

The ASTRI Prototype will allow us:

• to test the main innovative components with respect to the current

IACTs: the optical dual-mirror design, the SiPM-based focal plane, the

Front-End electronics and the software/data-handling architecture

• to obtain a direct measurement of prominent gamma-ray sources, such

as the Crab nebula, MRK 421 and MRK 501

The planned ASTRI mini-array, operated starting from 2016, will

constitute the first seed of the future CTA Project, and will be open to the

CTA Consortium for both technological and scientific exploitation.


The ASTRI Project

http://www.brera.inaf.it/astri/

THANKS!


The ASTRI Project

Extra-galactic mini-array science: AGN

Two possibilities to describe the

spectrum of 1ES 0229+200:

• γ–ray-induced cascade

• proton-induced cascade

Uncertainty in EBL model

difficult distinction at 0.1-1 TeV

E > 1 TeV:

• UHECR-induced cascade

emission harder than γ–ray-

induced cascade

• emission spectrum due to

injection of VHE/UHE photons

strongly suppressed at E > 10

TeV

detection at E > 25 TeV implies

hadronic origin of γ–rays


The ASTRI Project

Contributions to the Mini Array

• ASTRI consortium

• University of the Witwatersrand, Johannesburg, South Africa

• Brasil

• CHEC (Cherenkov High Energy Camera) – UK consortium

in kind contribution on cameras

• GATE SST group - Observatoire de Paris

in kind contribution on structures

• University of Amsterdam pending proposal for in-kind contribution

• CNEA, Argentina in-kind contribution

• DESY (MST) MOU under finalization


The ASTRI Project

CTA sensitivity in units of Crab flux

High-z AGN, GRBs, PSRs, DM

Population studies, extended sources, variability, precision TeV astronomy

Cut-off regime of CR accelerators


The ASTRI Project

CTA angular and spectral resolution


The ASTRI Project

Key science questions for CTA

• Where and how are the bulk of CR particles accelerated in the Galaxy

and beyond?

• How do cosmic rays propagate, interact, and heat the environment?

Which are the consequences from Galactic to cosmological scenarios?

• What makes black holes of all sizes such efficient particle accelerators?

• What do high-energy gamma-rays tell us about the star formation history

of the Universe, the structure of space-time, or the fundamental laws of

physics?

• What is the nature of the dark matter? Can it be discovered via indirect

searches? Can we map dark-matter halos?

• Are there short-timescale phenomena at very high energies? Are GRBs

gamma-ray emitters? Is there a new Galactic phenomenology to uncover?


The ASTRI Project

Science potential for CTA


The ASTRI Project

CTA performance goals

Improvement of angular resolution by a factor ~ 5 (from 0.1° to 0.02°)

substructure of SNR shock fronts can then be resolved

> 2.5 TeV 1 – 2.5 TeV < 1 TeV

Better understanding of the energy dependent morphology of Pulsar Wind Nebulae.

HESS J1825-137: PWN size decreases with energy:


The ASTRI Project


(Credit:X-ray: NASA/CXC/Rutgers/G.Cassam-Chenai, J.Hughes et al.;

Radio: NRAO/AUI/NSF/GBT/VLA/

Dyer, Maddalena & Cornwell;

Optical: Middlebury College/

F.Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS)

Resolving complex sources

SN 1006 — a

detected VHE

gamma-ray source

SN 1006

H.E.S.S. resolution

SN 1006

CTA resolution


The ASTRI Project


Aim: factor of 10 improvement in sensitivity.

Comparison of ~ 500 hour simulated HESS image of galactic plane...

...with simulation for the same exposure with higher CTA sensitivity:

Expectation to observe ~ 1000 sources (galactic and extra-galactic)


CR origin & prop.

PWN PSR physics microQSOs AGN physics GRB physics

Galaxy clusters Dark matter Cosmology & fundamental physics

The ASTRI Project

CTA science: expected contribution

1010 1011 1012 1013 1014 1015

MST

SST

LST

E (eV)


The ASTRI Project

The ASTRI Mirrors: panel manufacturing

Main steps of the panels manufacturing. From top-left, clockwise: mold

realization; front glass is made to adhere by vacuum suction to the mold;

the epoxy resin structural adhesive is spread on the glass; the Aluminum

honeycomb is positioned and the back glass foil is added on the top. The

resin is made polymerize with the proper curing cycle and sandwich is

finally released and coated. N. La Palombara –XCIX Congresso Nazionale della Società Italiana di Fisica –Trieste – 23-27 Settembre 2013

The Prototype Primary Mirror (M1)

The ASTRI Project

Primary mirror segment

off-axis aspherical profile obtained with the glass Cold-

Shaping technology at INAF – OA Brera

Physical Vapor Deposition of a multilayer of pure

dielectric materials

3D CAD model of the supporting and alignment structure of

the primary mirror segments. The triangular frame hosts two

motorized axial actuators for tip/tilt corrections and one

fixed point.


The Prototype Secondary

Mirror (M2)

The ASTRI Project

Scaled-down prototype of the

curved honeycomb core structure

of the monolithic secondary mirror

3D CAD view of the support and

alignment system of M2



The ASTRI Project

1 SiPM Unit 1 PDM Unit

(4x4 SiPMs) Matrix of 4x4 PDMs



The ASTRI Project

Drawing (left) and mock-up (right) of the

mechanical housing Sketch of the ASTRI Camera with

the Camera-Telescope I/F.

37 PDMs mounted on the mechanical housing


TeV γ-ray astronomy and the project ASTRI*/CTA - sif.it · TeV γ-ray astronomy and the project...

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