The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images

R. Morganti; T. A. Oosterloo; M. Brienza; N. Jurlin; I. Prandoni; E. Orrù; S. S. Shabala; E. A. K. Adams; B. Adebahr; P. N. Best; A. H. W. M. Coolen; S. Damstra; W. J. G. de Blok; F. de Gasperin; H. Dénes; M. Hardcastle; K. M. Hess; B. Hut; R. Kondapally; A. M. Kutkin; G. M. Loose; D. M. Lucero; Y. Maan; F. M. Maccagni; B. Mingo; V. A. Moss; R. I. J. Mostert; M. J. Norden; L. C. Oostrum; H. J. A. Röttgering; M. Ruiter; T. W. Shimwell; R. Schulz; N. J. Vermaas; D. Vohl; J. M. van der Hulst; G. M. van Diepen; J. van Leeuwen; J. Ziemke

doi:10.1051/0004-6361/202039102

The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images

R. Morganti^*, T. A. Oosterloo, M. Brienza, N. Jurlin, I. Prandoni, E. Orrù, S. S. Shabala, E. A. K. Adams, B. Adebahr, P. N. Best, A. H. W. M. Coolen, S. Damstra, W. J. G. de Blok, F. de Gasperin, H. Dénes, M. Hardcastle, K. M. Hess, B. Hut, R. Kondapally, A. M. KutkinG. M. Loose, D. M. Lucero, Y. Maan, F. M. Maccagni, B. Mingo, V. A. Moss, R. I. J. Mostert, M. J. Norden, L. C. Oostrum, H. J. A. Röttgering, M. Ruiter, T. W. Shimwell, R. Schulz, N. J. Vermaas, D. Vohl, J. M. van der Hulst, G. M. van Diepen, J. van Leeuwen, J. Ziemke

^*Corresponding author for this work

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Abstract

Super massive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei (AGN) is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of the images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within an approximately 6 deg² area of the Lockman Hole region. In this way, we were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent cases of radio sources in the remnant or the restarted phases of their life cycle. Our findings confirm that these objects are not as rare as previously thought, suggesting a relatively fast cycle. They also show a variety of properties that can be relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the "off" (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with the results of simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), possibly suggesting different types of progenitors. The present work sets the stage for exploiting the powerful tool of low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys.

The reduced APERTIF map is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A9

Original language	English
Pages (from-to)	A9
Journal	Astronomy & Astrophysics
Volume	648
DOIs	https://doi.org/10.1051/0004-6361/202039102
Publication status	Published - 1-Apr-2021

Keywords

radio continuum: galaxies
galaxies: active
Astrophysics - Astrophysics of Galaxies

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10.1051/0004-6361/202039102

The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index imagesFinal publisher's version, 33.9 MBLicence: Unspecified

https://ui.adsabs.harvard.edu/abs/2021A&A...648A...9M

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Lockman Hole Apertif map at 1.4GHz
Schulz, R. (Contributor), Kutkin, A. M. (Contributor), Oosterloo, T. A. (Contributor), Brienza, M. (Contributor), Coolen, A. H. W. M. (Contributor), Moss, V. A. (Contributor), Ruiter, M. (Contributor), Lucero, D. (Contributor), Röttgering, H. J. A. (Contributor), Hess, K. (Contributor), de Blok, E. (Contributor), Shabala, S. S. (Contributor), Morganti, R. (Contributor), Mostert, R. I. J. (Contributor), Jurlin, N. (Contributor), Mingo, B. (Contributor), Best, P. N. (Contributor), Orrù, E. (Contributor), Oostrum, L. C. (Contributor), Ziemke, J. (Contributor), Shimwell, T. W. (Contributor), van der Hulst, T. (Contributor), Van Diepen, G. M. (Contributor), De Gasperin, F. (Contributor), Prandoni, I. (Contributor), Maccagni, F. M. (Contributor), Dénes, H. (Contributor), Norden, M. J. (Contributor), Loose, G. M. (Contributor), Adams, B. (Contributor), Vohl, D. (Contributor), Hut, B. (Contributor), Maan, Y. (Contributor), Adebahr, B. (Contributor), Damstra, S. (Contributor), Hardcastle, M. (Contributor), Kondapally, R. (Contributor), Vermaas, N. J. (Contributor) & Van Leeuwen, J. (Contributor), Strasbourg Astronomical Data Center, 7-Apr-2021
DOI: 10.26093/cds/vizier.36480009
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Morganti, R., Oosterloo, T. A., Brienza, M., Jurlin, N., Prandoni, I., Orrù, E., Shabala, S. S., Adams, E. A. K., Adebahr, B., Best, P. N., Coolen, A. H. W. M., Damstra, S., de Blok, W. J. G., de Gasperin, F., Dénes, H., Hardcastle, M., Hess, K. M., Hut, B., Kondapally, R., ... Ziemke, J. (2021). The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images. Astronomy & Astrophysics, 648, A9. https://doi.org/10.1051/0004-6361/202039102

@article{2c3083d1a23a4325b5e4ca2032fa3eeb,

title = "The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images",

abstract = "Super massive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei (AGN) is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of the images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of \textasciitilde{}15 arcsec) for all the sources within an approximately 6 deg2 area of the Lockman Hole region. In this way, we were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent cases of radio sources in the remnant or the restarted phases of their life cycle. Our findings confirm that these objects are not as rare as previously thought, suggesting a relatively fast cycle. They also show a variety of properties that can be relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the {"}off{"} (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with the results of simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), possibly suggesting different types of progenitors. The present work sets the stage for exploiting the powerful tool of low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys. The reduced APERTIF map is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A9",

keywords = "radio continuum: galaxies, galaxies: active, Astrophysics - Astrophysics of Galaxies",

author = "R. Morganti and Oosterloo, \{T. A.\} and M. Brienza and N. Jurlin and I. Prandoni and E. Orr{\`u} and Shabala, \{S. S.\} and Adams, \{E. A. K.\} and B. Adebahr and Best, \{P. N.\} and Coolen, \{A. H. W. M.\} and S. Damstra and \{de Blok\}, \{W. J. G.\} and \{de Gasperin\}, F. and H. D{\'e}nes and M. Hardcastle and Hess, \{K. M.\} and B. Hut and R. Kondapally and Kutkin, \{A. M.\} and Loose, \{G. M.\} and Lucero, \{D. M.\} and Y. Maan and Maccagni, \{F. M.\} and B. Mingo and Moss, \{V. A.\} and Mostert, \{R. I. J.\} and Norden, \{M. J.\} and Oostrum, \{L. C.\} and R{\"o}ttgering, \{H. J. A.\} and M. Ruiter and Shimwell, \{T. W.\} and R. Schulz and Vermaas, \{N. J.\} and D. Vohl and \{van der Hulst\}, \{J. M.\} and \{van Diepen\}, \{G. M.\} and \{van Leeuwen\}, J. and J. Ziemke",

year = "2021",

month = apr,

day = "1",

doi = "10.1051/0004-6361/202039102",

language = "English",

volume = "648",

pages = "A9",

journal = "Astronomy \& Astrophysics",

issn = "0004-6361",

publisher = " EDP Sciences",

}

Morganti, R , Oosterloo, TA, Brienza, M, Jurlin, N, Prandoni, I, Orrù, E, Shabala, SS, Adams, EAK, Adebahr, B, Best, PN, Coolen, AHWM, Damstra, S, de Blok, WJG, de Gasperin, F, Dénes, H, Hardcastle, M, Hess, KM, Hut, B, Kondapally, R, Kutkin, AM, Loose, GM, Lucero, DM, Maan, Y, Maccagni, FM, Mingo, B, Moss, VA, Mostert, RIJ, Norden, MJ, Oostrum, LC, Röttgering, HJA, Ruiter, M, Shimwell, TW, Schulz, R, Vermaas, NJ, Vohl, D, van der Hulst, JM, van Diepen, GM, van Leeuwen, J & Ziemke, J 2021, 'The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images', Astronomy & Astrophysics, vol. 648, pp. A9. https://doi.org/10.1051/0004-6361/202039102

TY - JOUR

T1 - The best of both worlds

T2 - Combining LOFAR and Apertif to derive resolved radio spectral index images

AU - Morganti, R.

AU - Oosterloo, T. A.

AU - Brienza, M.

AU - Jurlin, N.

AU - Prandoni, I.

AU - Orrù, E.

AU - Shabala, S. S.

AU - Adams, E. A. K.

AU - Adebahr, B.

AU - Best, P. N.

AU - Coolen, A. H. W. M.

AU - Damstra, S.

AU - de Blok, W. J. G.

AU - de Gasperin, F.

AU - Dénes, H.

AU - Hardcastle, M.

AU - Hess, K. M.

AU - Hut, B.

AU - Kondapally, R.

AU - Kutkin, A. M.

AU - Loose, G. M.

AU - Lucero, D. M.

AU - Maan, Y.

AU - Maccagni, F. M.

AU - Mingo, B.

AU - Moss, V. A.

AU - Mostert, R. I. J.

AU - Norden, M. J.

AU - Oostrum, L. C.

AU - Röttgering, H. J. A.

AU - Ruiter, M.

AU - Shimwell, T. W.

AU - Schulz, R.

AU - Vermaas, N. J.

AU - Vohl, D.

AU - van der Hulst, J. M.

AU - van Diepen, G. M.

AU - van Leeuwen, J.

AU - Ziemke, J.

PY - 2021/4/1

Y1 - 2021/4/1

N2 - Super massive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei (AGN) is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of the images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within an approximately 6 deg2 area of the Lockman Hole region. In this way, we were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent cases of radio sources in the remnant or the restarted phases of their life cycle. Our findings confirm that these objects are not as rare as previously thought, suggesting a relatively fast cycle. They also show a variety of properties that can be relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the "off" (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with the results of simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), possibly suggesting different types of progenitors. The present work sets the stage for exploiting the powerful tool of low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys. The reduced APERTIF map is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A9

AB - Super massive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei (AGN) is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of the images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within an approximately 6 deg2 area of the Lockman Hole region. In this way, we were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent cases of radio sources in the remnant or the restarted phases of their life cycle. Our findings confirm that these objects are not as rare as previously thought, suggesting a relatively fast cycle. They also show a variety of properties that can be relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the "off" (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with the results of simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), possibly suggesting different types of progenitors. The present work sets the stage for exploiting the powerful tool of low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys. The reduced APERTIF map is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/648/A9

KW - radio continuum: galaxies

KW - galaxies: active

KW - Astrophysics - Astrophysics of Galaxies

U2 - 10.1051/0004-6361/202039102

DO - 10.1051/0004-6361/202039102

M3 - Article

SN - 0004-6361

VL - 648

SP - A9

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

ER -

The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images

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Lockman Hole Apertif map at 1.4GHz

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