Outline:

•Introduction into the problem

•Status of the identifications

•Summary

Identification of Very high Identification of Very high energy gamma-ray energy gamma-ray

sourcessources

Identification of Very high Identification of Very high energy gamma-ray energy gamma-ray

sourcessources

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

Unidentified sources

Unidentified sources

• During the first 2 years of operation of H.E.S.S. more than 15 (initially) unidentified gamma-ray sources were found

• Mostly found in the Galactic plane survey, but also some serendipitous discoveries in targeted observations on known sources

• Common properties of these sources:

• Positioned along the plane

• Most of the sources (at least) slightly extended

• Energy spectra generally hard (Photon index ~ 2.2)

H.E.S.S. plane survey

e.g. Kookaburra region

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

Identifying the sources

Identifying the sources

• Necessary for a firm identification: counterpart at other wavebands

• Step 1: Positional agreement. Good angular resolution helps against source confusion.

• Step 2: Viable gamma-ray emission mechanism of the positional counterpart

• Step 3: Consistent multi-wavelength picture

• Additionally: if extended - morphological match

• VHE gamma-astronomy in fortunate situation of “few” sources. For GLAST detailed case-by-case MWL studies for all sources is impossible.

H.E.S.SEGRET

The Crab Nebula

~ 0.1deg per event

H.E.S.SEGRET

The Crab Nebula

~ 0.1deg per eventPossible sources:

1.SNRs

2.Pulsars and PWN

3.Microquasars and binaries

4.Molecular clouds

5.Background AGN

6.Others?

Possible sources:

1. SNRs

2. Pulsars and PWN

3. Microquasars and binaries

4. Molecular clouds

5. Background AGN

6. Others?

• Most importantwavebands:

1.Radio

2.X-rays

• Timing information (periodicity or variability) can provide final proof

• Most importantwavebands:

1. Radio

2. X-rays

• Timing information (periodicity or variability) can provide final proof

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

Status of identification

Status of identification

• Following the scheme outlined before try to categorise the sources in the following scheme:

• CAT A: Perfect match (all items fulfilled plus morphological match for extended

sources)

• CAT B: Inconsistency in positional / morphological match

• CAT C: Inconsistency in multiwavelength picture

• CAT D: No match

Position

Emission

MWL

CAT Position/Morpholo

gy

Gamma-ray emission

mechanism

Consistent MWL

picture

ABCD

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

A: Perfect matchA: Perfect match• Extended Objects with (perfect) morphological match

to other wavebands (e.g. X-rays)

•

Association beyond doubt.

•

Associations with shell-type SNRs and with X-ray plerions

•

Gather MWL data to understand the emission mechanism

•

Probably not the typical objects for GLAST due to worse PSF

RX J1713.7-3946

Position

Emission

MWL

Vela X

RX J0852.0-4622

MSH 15-52

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

A: Perfect matchA: Perfect match• Extended Objects with (perfect) morphological match

to other wavebands (e.g. X-rays)

• Point-like objects - One counterpart candidate

•

Error on reconstructed position vs distance to the object.

•

Final proof from correlated variability (if exists) or periodicity.

•

Gather MWL data to understand the emission mechanism

•

GLAST likely to find sources of this category

RX J1713.7-3946

Position

Emission

MWLLS 5039

G0.9-0.1

RX J0852.0-4622

Vela X

MSH 15-52

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

A: Perfect matchA: Perfect match• Extended Objects with (perfect) morphological match

to other wavebands (e.g. X-rays)

• Point-like objects – One counterpart candidate

• Not quite perfect: Point-like objects – Source confusion

•

Arcmin angular resolution, Galactic Center still confused region

•

Only really identifiable via correlated variability in other wavebands

•

GLAST will be heavily facing this problem in the Galactic plane

RX J1713.7-3946

Position

Emission

MWL

Radio 90 cm - VLA VHE - H.E.S.S.Sgr A*

Sgr A East

LS 5039 G0.9-0.1

RX J0852.0-4622

Vela X

MSH 15-52

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

• H.E.S.S. sees several “offset” PWN, aroundenergetic pulsars, often with X-ray PWN.

• Archetypal example: HESS J1825-137

• Same morphology but vastly differentspatial scales for X-rays and -rays

• Reason could be different coolingtimescales for e- emitting synchrotron X-rays emitting IC gamma-rays

• Energy dependent morphology in gamma-raysaway from pulsar position supports this picture

• Here we can construct a plausible emission mechanism explaining the MWL data, but no direct morphological match

B: Problems in position/morphology

B: Problems in position/morphology

Position

Emission

MWL

XMM 2-10 keV

H.E.S.S. 0.25-30 TeV

1°

3’

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

• Example: HESS J1813-178

• Detected in plane survey, initially unidentified

• Shortly afterwards reports on a coincidentunidentified non-thermal strongly absorbedASCA and an INTEGRAL source

• Radio (VLA) data show shell-like structure.Another shell-type SNR emitting -rays?

C: Inconsistency in MWL pictureC: Inconsistency in MWL picture

Position

Emission

MWL

• XMM data show no shell but rather an extended object. Maybe another compositeSNR, but -rays (most) probably not from shell.

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

• The first example: HEGRA sourceTeV J2032+4131 in Cygnus region

• Another one: HESS J1303-631

• No counterpart so far, recentlyalso no counterpart in a 5 ks Chandra exposure.

• Claims of an associated GRB remnant …

• There are more of these objects. Currently obtaining XMM/Chandra/Suzaku data in a case-by-case effort.

• Still a long way to go …

D: UnidentifiedD: Unidentified

Position

Emission

MWL

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

The status so far …The status so far …

Position

Emission

MWL

Source CAT CommentJ1713-397 A SNR RX J1713.7-3946

J0852-463 A SNR RX J0852.0-4622

J0835-455 A PWN Vela X

J1514-591 A PWN MSH 15-52

J1826-148 A MQ LS 5039

J1302-638 A PWN PSR B1259-63

J1420-607 / J1418-609 A PWN Kookaburra

J1747-281 A PWN G0.9+0.1

J1825-137 B PWN different size in X-rays

J1804-216 B Possibly PWN or SNR?

+ several offset PWN B

J1813-178 C Maybe a composite SNR?

J1640-465 C Possibly an SNR, but insufficient MWL data

J1834-087 C

J1303-631 D

J1614-518 D

J1632-478 D

J1634-472 D

J1702-420 D

J1708-410 D

J1745-290 D Galactic Centre source

J1745-303 D

J1837-069 D

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006

• Categorise sources according to their identification status

• Clearly gathering good MWL data is the way to go to identify the H.E.S.S. unidentified sources.

• What will we learn for GLAST:

• Individual identification is very tedious, even with arcmin resolution

• Positional match does not suffice

• We need another approach than case-by-case MWL studies

• Nevertheless we will heavily depend on MWL catalogues for population studies

SummarySummary

Position

Emission

MWL