2010A&A...523A..46A

Query : 2010A&A...523A..46A

2010A&A...523A..46A - Astronomy and Astrophysics, volume 523, A46-46 (2010/11-2)

Detection of the Small Magellanic Cloud in gamma-rays with Fermi/LAT.

ABDO A.A., ACKERMANN M., AJELLO M., 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., BREZ A., BRIGIDA M., BRUEL P., BUEHLER R., BUSON S., CALIANDRO G.A., CAMERON R.A., CARAVEO P.A., CARRIGAN S., CASANDJIAN J.M., CECCHI C., CELIK O., CHARLES E., CHEKHTMAN A., CHEUNG C.C., CHIANG J., CIPRINI S., CLAUS R., COHEN-TANUGI J., CONRAD J., DERMER C.D., DE PALMA F., DIGEL S.W., DO COUTO E SILVA E., DRELL P.S., DUBOIS R., DUMORA D., FAVUZZI C., FEGAN S.J., FUKAZAWA Y., FUNK S., FUSCO P., GARGANO F., GASPARRINI D., GEHRELS N., GERMANI S., GIGLIETTO N., GIORDANO F., GIROLETTI M., GLANZMAN T., GODFREY G., GRENIER I.A., GRONDIN M.-H., GROVE J.E., GUIRIEC S., HADASCH D., HARDING A.K., HAYASHIDA M., HAYS E., HORAN D., HUGHES R.E., JEAN P., JOHANNESSON G., JOHNSON A.S., JOHNSON W.N., KAMAE T., KATAGIRI H., KATAOKA J., KERR M., KNOEDLSEDER J., KUSS M., LANDE J., LATRONICO L., LEE S.-H., LEMOINE-GOUMARD M., LLENA GARDE M., LONGO F., LOPARCO F., LOVELLETTE M.N., LUBRANO P., MAKEEV A., MARTIN P., MAZZIOTTA M.N., McENERY J.E., MICHELSON P.F., MITTHUMSIRI W., MIZUNO T., MONTE C., MONZANI M.E., MORSELLI A., MOSKALENKO I.V., MURGIA S., NAKAMORI T., NAUMANN-GODO M., NOLAN P.L., NORRIS J.P., NUSS E., OHSUGI T., OKUMURA A., OMODEI N., ORLANDO E., ORMES J.F., PANETTA J.H., PARENT D., PELASSA V., PEPE M., PESCE-ROLLINS M., PIRON F., PORTER T.A., RAINO S., RANDO R., RAZZANO M., REIMER A., REIMER O., REPOSEUR T., RIPKEN J., RITZ S., ROMANI R.W., SADROZINSKI H.F.-W., SANDER A., SAZ PARKINSON P.M., SCARGLE J.D., SGRO C., SISKIND E.J., SMITH D.A., SMITH P.D., SPANDRE G., SPINELLI P., STRICKMAN M.S., STRONG A.W., SUSON D.J., TAKAHASHI H., TAKAHASHI T., TANAKA T., THAYER J.B., THAYER J.G., THOMPSON D.J., TIBALDO L., TORRES D.F., TOSTI G., TRAMACERE A., UCHIYAMA Y., USHER T.L., VANDENBROUCKE J., VASILEIOU V., VILCHEZ N., VITALE V., WAITE A.P., WANG P., WINER B.L., WOOD K.S., YANG Z., YLINEN T. and ZIEGLER M.

Abstract (from CDS):

The flux of gamma rays with energies greater than 100MeV is dominated by diffuse emission coming from cosmic-rays (CRs) illuminating the interstellar medium (ISM) of our Galaxy through the processes of Bremsstrahlung, pion production and decay, and inverse-Compton scattering. The study of this diffuse emission provides insight into the origin and transport of cosmic rays. We searched for gamma-ray emission from the Small Magellanic Cloud (SMC) in order to derive constraints on the cosmic-ray population and transport in an external system with properties different from the Milky Way.We analysed the first 17 months of continuous all-sky observations by the Large Area Telescope (LAT) of the Fermi mission to determine the spatial distribution, flux and spectrum of the gamma-ray emission from the SMC. We also used past radio synchrotron observations of the SMC to study the population of CR electrons specifically. We obtained the first detection of the SMC in high-energy gamma rays, with an integrated >100MeV flux of (3.7±0.7)x10^–8ph/cm²/s, with additional systematic uncertainty of ≤16%. The emission is steady and from an extended source ∼3° in size. It is not clearly correlated with the distribution of massive stars or neutral gas, nor with known pulsars or supernova remnants, but a certain correlation with supergiant shells is observed.The observed flux implies an upper limit on the average CR nuclei density in the SMC of ∼15% of the value measured locally in the Milky Way. The population of high-energy pulsars of the SMC may account for a substantial fraction of the gamma-ray flux, which would make the inferred CR nuclei density even lower. The average density of CR electrons derived from radio synchrotron observations is consistent with the same reduction factor but the uncertainties are large. From our current knowledge of the SMC, such a low CR density does not seem to be due to a lower rate of CR injection and rather indicates a smaller CR confinement volume characteristic size.

Abstract Copyright: ∼

Journal keyword(s): acceleration of particles - cosmic rays - Magellanic Clouds - gamma rays: general

Simbad objects: 12

Full paper

View the references in ADS

Number of rows : 12

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag U	Mag B	Mag V	Mag R	Sp type	#ref 1850 - 2023	#notes
1	NGC 104	GlC	00 24 05.359	-72 04 53.20			4.09		~	3842	0
2	NAME SMC B0026-7101	Bla	00 28 41.5636966584	-70 45 15.927580080				16.62	~	37	0
3	NAME SMC	G	00 52 38.0	-72 48 01		2.79	2.2		~	10848	1
4	NGC 346	Cl*	00 59 04.4000	-72 10 39.000					~	479	0
5	PSR J0100-7211	Psr	01 00 42.86	-72 11 33.3		17.69	17.82		B3V	93	0
6	PSR J0101-6422	Psr	01 01 11.1163	-64 22 30.171					~	48	0
7	2FGL J0216.9-6630	BLL	02 16 50.86999	-66 36 42.6002	17.96	17.44	17.57		~	39	0
8	NAME Magellanic Clouds	GrG	03 00	-71.0					~	6829	1
9	NAME LMC	G	05 23 34.6	-69 45 22			0.4		~	16986	1
10	QSO J2147-7536	QSO	21 47 12.73063669	-75 36 13.2249063		17.79	17.30		~	136	1
11	1FGL J2227.4-7804	BLL	22 30 30.54827	-78 15 56.5795					~	24	0
12	1FGL J2355.9-6613	gam	23 53 43.06	-66 14 31.1					~	15	0

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