101 102 103

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100

101

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F1

uGMRT Observations of the Prospective SNR Candidate G351.7-1.2 ! Veena V. S.1, S. Vig1, B. Sebastian2, D. V. Lal2, A. Tej1, S. K. Ghosh3!

!1Indian Institute of Space science andTechnology (IIST), Thiruvananthapuram, 2NCRA-TIFR, Pune, 3TIFR, Mumbai

AbstractThe massive stars and OB clusters profoundly affect their environments through extreme UV radiation, stellar winds, and eventually by supernova explosions. The blast waves from supernova explosions tend to disrupt the parental molecular cloud, thus terminating the ongoing/future star formation processes. However, these explosions could also drive an intense burst of star formation where a part of the molecular cloud is dense enough to survive the explosion. Such systems provide a great opportunity to study the complex interaction mechanisms between the supernova blast wave and the ambient cloud. In this poster, we report the presence of a new SNR candidate G351.7-1.2 that is associated with massive star forming complexes in its vicinity. The massive star forming complex include the two HII regions: IRAS 17258-3637 and IRAS 17256-3631. Both these regions are active sites of high mass star formation that harbour young embedded clusters (Vig et al. 2014, Veena et al. 2016). In order to examine the nature of radio emission associated with these regions, we have probed this region with the upgraded Giant Metrewave Radio Telescope (uGMRT, Pune). Combining this with the optical, infrared and submillimeter data, we present a multiwavelength investigation of the region.

Ionised Gas Emission

Spectral Index Analysis

320 400 500Frequency (MHz)

2.0

3.0

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A6 (α = −0.90± 0.14)

320 400 500Frequency (MHz)

1.0

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A5 (α = −1.73± 0.21)

320 400 500Frequency (MHz)

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A3 (α = −0.57± 0.17)

320 400 500Frequency (MHz)

2.0

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A2 (α = 1.00± 0.06)

320 400 500Frequency (MHz)

2.0

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A1 (α = 0.65± 0.06)

320 400 500Frequency (MHz)

0.4

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A4 (α = −1.39± 0.37)

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Radio shell (α = −0.79± 0.06) Aperture Spectral index α1 (17256-3631) 0.69±0.052 (17258-3637) 0.98±0.07

3 -0.57±0.184 -1.23±0.415 -1.79±0.196 -0.99±0.14

Radio shell -0.79±0.06

Emission from Dust

Radio continuum maps of G351.7-1.2 at 321, 351, 385, 418, 450 and 480 MHz. The two HII regions associated with this complex, IRAS 17256-3631 and IRAS 17258-3637 are marked and labelled in panel (a). The dashed arc shows the approximate position of diffuse ionised shell. Panel (b) shows 6 apertures whose spectral indices are listed in Table. The beam is shown as an ellipse in the bottom left corner of panel (d).

Radio spectra of the 6 apertures and the full radio shell using fluxes at 6 bands. The spectral indices of the HII regions (apertures 1 and 2) are consistent with thermal free-free emission. Spectral indices in the diffuse radio shell indicate non-thermal emission.

Hα image of 351.7-1.2 (dotted circle) overlaid with 321 MHz radio contours. Ellipse denotes the location of Fermi-LAT γ-ray source. Two HII regions are marked as X.

Discussions• From low frequency (300-500 MHz) wide band observations using upgraded GMRT, we

have identified a new ionised shell (radius ~ 4 pc) associated with the star forming regions IRAS 17256-3631 and IRAS 17258-3637!

!• Radio spectral index analysis point towards the non-thermal nature (α~-0.8) of the radio

shell!!• Morphologically similar optical counterpart is detected in the Hα image!!• The radio shell and its optical counterpart are likely to be tracing emission from a previously

unidentified supernova remnant SNRG351.7-1.2!!• A γ-ray source 1FGLJ1729.1-3641c is located towards the south-west of the radio shell and

is likely associated with the SNR candidate itself

Radio (321 MHz) - red!Mid-infrared (4.5 μm) -

Multiwavelength view of SNR G351.7 and its surroundings. Panels (a), (b), (c) and (d) corresponds to mid-infrared emission from MSX. Panels (e) and (f) shows cold dust emission mapped using Herschel. Dotted circle denotes the approximate location of Hα shell. Triangle in panel (b) shows the location of the γ-ray source. Ellipse in panel (c)shows the bright arc-like feature F1 seen in the periphery of Hα shell. Other IRAS sources in the field are marked as crosses in panel (d).

The temperature of warm dust along the arc-like feature F1 is estimated using a two-component modified blackbody fit.!!Temperature of warmer component: 153.1±7.9 K!Temperature of colder component: 31.6±1.9K!!Presence of warm dust component indicates collisional heating/radiative shocks

!• Shock heated mid-infrared dust emission

is seen towards the region and cold dust emission is only detected towards the west of the SNR that could explain the broken-shell morphology of this object !!

• The SNR progenitor is likely to be an older generation star in the giant molecular cloud associated with the nearby star forming complexes!

!

The optical emission associated with G351.7-1.2 is identified using the archival images taken from SuperCOSMOS Hα survey. The Hα shell overlaps with the inner edge of the radio shell. The angular size of the shell is 5.6 arcmin, that corresponds to 3.3 pc for a distance of 2 kpc (assuming the same distance as that of nearby HII regions).!!A γ-ray source 1FGLJ1729.1-3641c has been found that is located towards the south-west of the radio shell. Although, the angular resolution (0.1 deg) is insufficient to pinpoint its origin, the γ-ray has likely genesis at the site where SNR interacts with the ambient molecular cloud.

References!!• Veena V. S., Vig S., Tej A., Varricatt W. P., Ghosh S. K., Chandrasekhar T., Ashok N. M., 2016,

MNRAS, 456, 2425!• Vig S., Ghosh S. K., Ojha D. K., Verma R. P., Tamura M., 2014, MNRAS, 440, 3078