A low-frequency study of recently identified double-double radio galaxies. (arXiv:1905.00677v1 [astro-ph.GA])

A low-frequency study of recently identified double-double radio galaxies. (arXiv:1905.00677v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Nandi_S/0/1/0/all/0/1">S. Nandi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saikia_D/0/1/0/all/0/1">D.J. Saikia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roy_R/0/1/0/all/0/1">R. Roy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dabhade_P/0/1/0/all/0/1">P. Dabhade</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wadadekar_Y/0/1/0/all/0/1">Y. Wadadekar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Larsson_J/0/1/0/all/0/1">J. Larsson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baes_M/0/1/0/all/0/1">M. Baes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chandola_H/0/1/0/all/0/1">H.C. Chandola</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Singh_M/0/1/0/all/0/1">M. Singh</a>

In order to understand the possible mechanisms of recurrent jet activity in
radio galaxies and quasars, which are still unclear, we have identified such
sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time
scales of episodic activity. Here we present high-sensitivity 607-MHz Giant
Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio
galaxies (DDRGs) identified from the FIRST survey to confirm their episodic
nature. These GMRT observations show that none of the inner compact components
suspected to be hot-spots of the inner doubles are cores having a flat radio
spectrum, confirming the episodic nature of these radio sources. We have
indentified a new DDRG with a candidate quasar, and have estimated the upper
spectral age limits for eight sources which showed marginal evidence of
steepening at higher frequencies. The estimated age limits (11 $-$ 52 Myr) are
smaller than those of the large-sized ($sim$ 1 Mpc) DDRGs.

In order to understand the possible mechanisms of recurrent jet activity in
radio galaxies and quasars, which are still unclear, we have identified such
sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time
scales of episodic activity. Here we present high-sensitivity 607-MHz Giant
Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio
galaxies (DDRGs) identified from the FIRST survey to confirm their episodic
nature. These GMRT observations show that none of the inner compact components
suspected to be hot-spots of the inner doubles are cores having a flat radio
spectrum, confirming the episodic nature of these radio sources. We have
indentified a new DDRG with a candidate quasar, and have estimated the upper
spectral age limits for eight sources which showed marginal evidence of
steepening at higher frequencies. The estimated age limits (11 $-$ 52 Myr) are
smaller than those of the large-sized ($sim$ 1 Mpc) DDRGs.

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