2010A&A...523L...2A

Query : 2010A&A...523L...2A

2010A&A...523L...2A - Astronomy and Astrophysics, volume 523, L2-2 (2010/11-2)

Fermi Large Area Telescope observations of Local Group galaxies: detection of M31 and search for M33.

ABDO A.A., ACKERMANN M., AJELLO M., ALLAFORT A., ATWOOD W.B., BALDINI L., BALLET J., BARBIELLINI G., BASTIERI D., BECHTOL K., BELLAZZINI R., BERENJI B., BLANDFORD R.D., BLOOM E.D., BONAMENTE E., BORGLAND A.W., BOUVIER A., BRANDT T.J., BREGEON J., BRIGIDA M., BRUEL P., BUEHLER R., BURNETT T.H., BUSON S., CALIANDRO G.A., CAMERON R.A., CANNON A., CARAVEO P.A., CASANDJIAN J.M., CECCHI C., CELIK O., CHARLES E., CHEKHTMAN A., CHIANG J., CIPRINI S., CLAUS R., COHEN-TANUGI J., CONRAD J., DERMER C.D., DE ANGELIS A., DE PALMA F., DIGEL S.W., DO COUTO E SILVA E., DRELL P.S., DRLICA-WAGNER A., DUBOIS R., FAVUZZI C., FEGAN S.J., FORTIN P., FRAILIS M., FUKAZAWA Y., FUNK S., FUSCO P., GARGANO F., GERMANI S., GIGLIETTO N., GIORDANO F., GIROLETTI M., GLANZMAN T., GODFREY G., GRENIER I.A., GRONDIN M.-H., GUIRIEC S., GUSTAFSSON M., HADASCH D., HARDING A.K., HAYASHI K., HAYASHIDA M., HAYS E., HEALEY S.E., JEAN P., JOHANNESSON G., JOHNSON A.S., JOHNSON R.P., JOHNSON T.J., KAMAE T., KATAGIRI H., KATAOKA J., KERR M., KNOEDLSEDER J., KUSS M., LANDE J., LATRONICO L., LEE S.-H., LEMOINE-GOUMARD M., LONGO F., LOPARCO F., LOTT B., LOVELLETTE M.N., LUBRANO P., MADEJSKI G.M., MAKEEV A., MARTIN P., MAZZIOTTA M.N., MEHAULT J., MICHELSON P.F., MITTHUMSIRI W., MIZUNO T., MOISEEV A.A., MONTE C., MONZANI M.E., MORSELLI A., MOSKALENKO I.V., MURGIA S., NAUMANN-GODO M., NOLAN P.L., NORRIS J.P., NUSS E., OHSUGI T., OKUMURA A., OMODEI N., ORLANDO E., ORMES J.F., OZAKI M., PANEQUE D., PANETTA J.H., PARENT D., PEPE M., PERSIC M., PESCE-ROLLINS M., PIRON F., PORTER T.A., RAINO S., RANDO R., RAZZANO M., REIMER A., REIMER O., RITZ S., ROMANI R.W., SADROZINSKI H.F.-W., SAZ PARKINSON P.M., SGRO C., SISKIND E.J., SMITH D.A., SMITH P.D., SPANDRE G., SPINELLI P., STRICKMAN M.S., STRIGARI L., STRONG A.W., SUSON D.J., TAKAHASHI H., TAKAHASHI T., TANAKA T., THAYER J.B., THOMPSON D.J., TIBALDO L., TORRES D.F., TOSTI G., TRAMACERE A., UCHIYAMA Y., USHER T.L., VANDENBROUCKE J., VIANELLO G., VILCHEZ N., VITALE V., WAITE A.P., WANG P., WINER B.L., WOOD K.S., YANG Z. and ZIEGLER M.

Abstract (from CDS):

Cosmic rays (CRs) can be studied through the galaxy-wide gamma-ray emission that they generate when propagating in the interstellar medium. The comparison of the diffuse signals from different systems may inform us about the key parameters in CR acceleration and transport. We aim to determine and compare the properties of the cosmic-ray-induced gamma-ray emission of several Local Group galaxies. We use 2 years of nearly continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope to search for gamma-ray emission from M31 and M33. We compare the results with those for the Large Magellanic Cloud, the Small Magellanic Cloud, the Milky Way, and the starburst galaxies M82 and NGC 253. We detect a gamma-ray signal at 5σ significance in the energy range 200MeV-20GeV that is consistent with originating from M31. The integral photon flux above 100 MeV amounts to (9.1±1.9_stat±1.0_sys)x10^–9ph/cm²/s. We find no evidence for emission from M33 and derive an upper limit on the photon flux>100MeV of 5.1x10^–9ph/cm²/s (2σ). Comparing these results to the properties of other Local Group galaxies, we find indications of a correlation between star formation rate and gamma-ray luminosity that also holds for the starburst galaxies. The gamma-ray luminosity of M31 is about half that of the Milky Way, which implies that the ratio between the average CR densities in M31 and the Milky Way amounts to ξ=0.35±0.25. The observed correlation between gamma-ray luminosity and star formation rate suggests that the flux of M33 is not far below the current upper limit from the LAT observations.

Abstract Copyright: ∼

Journal keyword(s): Local Group - cosmic rays - gamma rays: galaxies

Simbad objects: 15

Full paper

View the references in ADS

Number of rows : 15

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag U	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2024	#notes
1	7C 002055.00+444012.00	QSO	00 23 35.44247367	+44 56 35.7581986				21.70		~	59	1
2	5C 3.76	BLL	00 40 13.800	+40 50 04.73			19.30	19.9		~	67	1
3	M 31	AGN	00 42 44.330	+41 16 07.50	4.86	4.36	3.44			~	12475	1
4	NGC 253	SyG	00 47 33.134	-25 17 19.68		8.03		6.94	8.1	~	3278	2
5	NAME SMC	G	00 52 38.0	-72 48 01		2.79	2.2			~	10928	1
6	NAME CRATES J0102+4214	QSO	01 02 27.1487492736	+42 14 18.984248160				19		~	43	1
7	87GB 010219.8+391221	Bla	01 05 09.1962613704	+39 28 15.320001180			19.69	18.2		~	40	1
8	4C 31.03	Bla	01 12 50.3328920232	+32 08 17.435303556			18.0	18.1		~	115	1
9	M 33	GiG	01 33 50.8965749232	+30 39 36.630403128	6.17	6.27	5.72			~	5764	1
10	RX J0134.4+2638	BLL	01 34 28.1946775464	+26 38 43.010995272		17.1		15.9		~	53	0
11	ICRF J014433.5+270503	BLL	01 44 33.55384903	+27 05 03.1179726				18.6		~	82	1
12	NAME LMC	G	05 23 34.6	-69 45 22			0.4			~	17109	1
13	RMC 136	Cl*	05 38 42.396	-69 06 03.36		5.81	5.40			~	1979	2
14	M 82	AG?	09 55 52.430	+69 40 46.93	9.61	9.30	8.41			~	5781	6
15	NAME Local Group	GrG	~	~						~	8225	0

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