Outline: Introduction into the problem Status of the identifications Summary Identification of Very high energy gamma-ray sources

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 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 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.S EGRET The Crab Nebula ~ 0.1deg per event H.E.S.S EGRET The Crab Nebula ~ 0.1deg per event Possible 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 important wavebands: 1.Radio 2.X-rays Timing information (periodicity or variability) can provide final proof Most important wavebands: 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 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 PositionEmissionMWL CATPosition/ Morphology Gamma-ray emission mechanism Consistent MWL picture A B C D

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 A: 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 J Position Emission MWL Vela X RX J MSH 15-52

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 A: 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 J Position Emission MWL LS 5039 G RX J Vela X MSH 15-52

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 A: 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 J Position Emission MWL Radio 90 cm - VLA VHE  - H.E.S.S. Sgr A* Sgr A East LS 5039G RX J 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, around energetic pulsars, often with X-ray PWN. Archetypal example: HESS J Same morphology but vastly different spatial scales for X-rays and  -rays Reason could be different cooling timescales for e - emitting synchrotron X-rays emitting IC gamma-rays Energy dependent morphology in gamma-rays away 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 Position Emission MWL XMM 2-10 keV H.E.S.S TeV 1° 3’

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 Example: HESS J Detected in plane survey, initially unidentified Shortly afterwards reports on a coincident unidentified non-thermal strongly absorbed ASCA and an INTEGRAL source Radio (VLA) data show shell-like structure. Another shell-type SNR emitting  -rays? C: Inconsistency in MWL picture Position Emission MWL XMM data show no shell but rather an extended object. Maybe another composite SNR, but  -rays (most) probably not from shell.

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 The first example: HEGRA source TeV J in Cygnus region Another one: HESS J No counterpart so far, recently also 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: Unidentified Position Emission MWL

Stefan Funk – The multi-messenger approach to unidentified gamma-ray sources – Barcelona 2006 The status so far … Position Emission MWL SourceCATComment J ASNR RX J J ASNR RX J J APWN Vela X J APWN MSH J AMQ LS 5039 J APWN PSR B J / J APWN Kookaburra J APWN G J BPWN different size in X-rays J BPossibly PWN or SNR? + several offset PWNB J CMaybe a composite SNR? J CPossibly an SNR, but insufficient MWL data J C J D J D J D J D J D J D J DGalactic Centre source J D J 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 Summary Position Emission MWL