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Nandi, Sumana
Publications (2 of 2) Show all publications
Nandi, S., Saikia, D. J., Roy, R., Dabhade, P., Wadadekar, Y., Larsson, J., . . . Singh, M. (2019). A low-frequency study of recently identified double-double radio galaxies. Monthly notices of the Royal Astronomical Society, 486(4), 5158-5170
Open this publication in new window or tab >>A low-frequency study of recently identified double-double radio galaxies
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 4, p. 5158-5170Article in journal (Refereed) Published
Abstract [en]

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 timescales 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 hotspots of the inner doubles are cores having a flat radio spectrum, confirming the episodic nature of these radio sources, We have identified 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 (similar to 1 Mpc) DDRGs.

Place, publisher, year, edition, pages
Oxford University Press, 2019
Keywords
galaxies: active, galaxies: evolution, galaxies. jets, galaxies: nuclei, (galaxies.) quasars: supermassive black holes, radio continuum: galaxies.
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255573 (URN)10.1093/mnras/stz1184 (DOI)000474908200053 ()2-s2.0-85068008633 (Scopus ID)
Note

QC 20190802

Available from: 2019-08-02 Created: 2019-08-02 Last updated: 2019-08-02Bibliographically approved
Nandi, S., Jamrozy, M., Roy, R., Larsson, J., Saikia, D. J., Baes, M. & Singh, M. (2017). Tale of J1328+2752: a misaligned double-double radio galaxy hosted by a binary black hole?. Monthly notices of the Royal Astronomical Society, 467(1), L56-L60
Open this publication in new window or tab >>Tale of J1328+2752: a misaligned double-double radio galaxy hosted by a binary black hole?
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 467, no 1, p. L56-L60Article in journal (Refereed) Published
Abstract [en]

We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency Giant Metrewave Radio Telescope observations and Sloan Digital Sky Survey (SDSS) data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source, we find that the inner double is misaligned by similar to 30 degrees from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity offset of the two components is 235 +/- 10.5 kms(-1). The misaligned radio morphology along with the double-peaked emission lines indicate that this source is a potential candidate binary supermassive black hole. This study further supports mergers as a possible explanation for repeated jet activity in radio sources.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS, 2017
Keywords
line: identification, line: profiles, galaxies: active, galaxies: individual: J1328+2752, galaxies: nuclei, radio continuum: galaxies
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-215485 (URN)10.1093/mnrasl/slw256 (DOI)000410063700012 ()2-s2.0-85018296806 (Scopus ID)
Note

QC 20171013

Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2017-10-23Bibliographically approved
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