2023A&A...671A..47A


Query : 2023A&A...671A..47A

2023A&A...671A..47A - Astronomy and Astrophysics, volume 671A, 47 (2023/3-1)

Multiple emission components in the Cygnus cocoon detected from Fermi-LAT observations.

ASTIASARAIN X., TIBALDO L., MARTIN P., KNODLSEDER J. and REMY Q.

Abstract (from CDS):

Context. Star-forming regions may play an important role in the life cycle of Galactic cosmic rays (CRs), notably as home to specific acceleration mechanisms and transport conditions. Gamma-ray observations of Cygnus X have revealed the presence of an excess of hard-spectrum gamma-ray emission, possibly related to a cocoon of freshly accelerated particles.
Aims. We seek an improved description of the gamma-ray emission from the cocoon using ∼13 yr of observations with the Fermi-Large Area Telescope (LAT) and use it to further constrain the processes and objects responsible for the young CR population.
Methods. We developed an emission model for a large region of interest, including a description of interstellar emission from the background population of CRs and recent models for other gamma-ray sources in the field. Thus, we performed an improved spectro-morphological characterisation of the residual emission including the cocoon.
Results. The best-fit model for the cocoon includes two main emission components: an extended component FCES G78.74+1.56, described by a 2D Gaussian of extension r68 = 4.4° ± 0.1°–0.1°+0.1° and a smooth broken power law spectrum with spectral indices 1.67 ± 0.05–0.01+0.02 and 2.12 ± 0.02–0.01+0.00 below and above 3.0 ± 0.6–0.2+0.0 GeV, respectively; and a central component FCES G80.00+0.50, traced by the distribution of ionised gas within the borders of the photo-dissociation regions and with a power law spectrum of index 2.19 ± 0.03–0.01+0.00 that is significantly different from the spectrum of FCES G78.74+1.56. An additional extended emission component FCES G78.83+3.57, located on the edge of the central cavities in Cygnus X and with a spectrum compatible with that of FCES G80.00+0.50, is likely related to the cocoon. For the two brightest components FCES G80.00+0.50 and FCES G78.74+1.56, spectra and radial-azimuthal profiles of the emission can be accounted for in a diffusion-loss framework involving one single population of non-thermal particles with a flat injection spectrum. Particles span the full extent of FCES G78.74+1.56 as a result of diffusion from a central source, and give rise to source FCES G80.00+0.50 by interacting with ionised gas in the innermost region.
Conclusions. For this simple diffusion-loss model, viable setups can be very different in terms of energetics, transport conditions, and timescales involved, and both hadronic and leptonic scenarios are possible. The solutions range from long-lasting particle acceleration, possibly in prominent star clusters such as Cyg OB2 and NGC 6910, to a more recent and short-lived release of particles within the last 10-100 kyr, likely from a supernova remnant. The observables extracted from our analysis can be used to perform detailed comparisons with advanced models of particle acceleration and transport in star-forming regions.

Abstract Copyright: © The Authors 2023

Journal keyword(s): acceleration of particles - cosmic rays - gamma rays: ISM - open clusters and associations: individual: Cygnus OB2 - open clusters and associations: individual: NGC 6910

VizieR on-line data: <Available at CDS (J/A+A/671/A47): pg78p74.dat pg80p00.dat g78p74.dat g78p83.dat g80p00.dat g85p00.dat list.dat fits/*>

Status at CDS : Examining the need for a new acronym. // Tables of objects will be appraised for possible ingestion in SIMBAD.

Simbad objects: 22

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Number of rows : 22
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 NAME Per Arm PoG 03 30 +45.0           ~ 1519 0
2 NAME Geminga Psr 06 33 54.153 +17 46 12.91           ~ 1224 0
3 PSR B0656+14 Psr 06 59 48.1960 +14 14 19.400   24.85 24.90     ~ 874 1
4 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
5 PSR B1823-13 Psr 18 26 13.06 -13 34 48.1           ~ 421 1
6 PSR J1957+5033 Psr 19 57 38.391 +50 33 21.24           ~ 37 0
7 IC 1318 HII 20 16 48 +41 57.4           ~ 44 0
8 Ass Cyg OB 1 As* 20 17.8 +37 38           ~ 264 1
9 NAME gam Cyg SNR BL? 20 20 17.100 +40 26 09.00           ~ 229 2
10 PSR J2021+3651 Psr 20 21 05.40 +36 51 04.5           ~ 191 1
11 PSR J2021+4026 Psr 20 21 30.496 +40 26 53.56           ~ 275 2
12 * gam Cyg V* 20 22 13.7018357 +40 15 24.044963 3.44 2.90 2.23 1.74 1.40 F8Ib 583 0
13 NGC 6910 OpC 20 23 11 +40 46.3           ~ 193 0
14 NAME Cyg X BL? 20 30 04.7973633 +40 51 36.002197           ~ 848 1
15 NAME Cyg Complex reg 20 32 +45.0           ~ 602 0
16 [MT91] 213 Psr 20 32 13.1247390384 +41 27 24.346666440 13.12 13.08 11.266     B0Vp 290 0
17 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 945 0
18 SNR G089.0+04.7 SNR 20 45.0 +50 35           ~ 224 0
19 NAME Cyg Loop SNR 20 51.0 +30 40           ~ 913 0
20 PSR J2111+4606 Psr 21 11 24.125 +46 06 30.66           ~ 39 0
21 NAME IV CYG ASSOC. As* 21 15 +37.9           ~ 48 0
22 NGC 7082 OpC 21 28 44.6 +47 06 11   7.70 7.2     ~ 56 0

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