High frequency peakers

Orienti, M.

doi:10.1002/asna.200811147

Cited by 9 publications

(10 citation statements)

References 36 publications

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“…compact objects with a simple convex radio spectrum turning over at frequencies well above a few GHz, which likely represent the earliest stage in individual radio source evolution (e.g. Dallacasa et al 2000;Orienti 2009). While this should be checked with further simultaneous multiwaveband observations, as a matter of fact, its spectral shape above 5 GHz is inverted, as measured by simultaneous multiwavelength observations with Effelsberg 100-m telescope by Neumann et al (1994).…”

Section: Individual Objectsmentioning

confidence: 99%

The Compact Radio Structure of Radio-Loud Narrow Line Seyfert 1 Galaxies

Chen

2010

The Astronomical Journal

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We present the compact radio structure of three radio-loud narrow line Seyfert 1 galaxies from VLBA archive data at 2.3, 5 and 8.4 GHz. In RXS J16290+4007, the radio structure is mostly unresolved. The combination of compact radio structure, high brightness temperature and inverted spectrum between simultaneous 2.3 and 8.4 GHz, strongly favors jet relativistic beaming. Combining with the VLBI data at 1.6 and 8.4 GHz from literatures, we argued that RXS J16333+4718 may also harbor a relativistic jet, with resolved core-jet structure in 5 GHz. B3 1702+457 is clearly resolved with well defined jet component. The overall radio steep spectrum indicates that B3 1702+457 is likely a source optically defined as NLS1 with radio definition of compact steep spectrum sources. From these three sources, we found that radio loud NLS1s can be either intrinsically radio loud (e.g. B3 1702+457), or apparently radio loud due to jet beaming effect (e.g. RXS J16290+4007 and RXS J16333+4718).

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Section: Individual Objectsmentioning

confidence: 99%

The Compact Radio Structure of Radio-Loud Narrow Line Seyfert 1 Galaxies

Chen

2010

The Astronomical Journal

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“…While some early‐type galaxies are known from targeted searches to have significant H i content, particularly in the field (e.g. Morganti et al 2006; Orienti et al 2007), blind surveys, such as the Arecibo Legacy Fast ALFA (ALFALFA) survey (di Serego Alighieri et al 2007), show that early‐type galaxies in clusters have a much lower neutral gas content. Those quasars with detected H i absorption are then more likely to be found in discy or late‐type galaxies.…”

Section: Possible Effects In the Non‐detection Of Atomic Absorptionmentioning

confidence: 99%

A survey for redshifted molecular and atomic absorption lines - II. Associated H i, OH and millimetre lines in thez≳ 3 Parkes quarter-Jansky flat-spectrum sample

Curran

Whiting

Wiklind

et al. 2008

Monthly Notices of the Royal Astronomical Society

116

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We present the results of a z≥ 2.9 survey for H i 21‐cm and molecular absorption in the hosts of radio quasars using the Giant Metrewave Radio Telescope and the Tidbinbilla 70‐m telescope. Although the atomic gas has been searched to limits capable of detecting most known absorption systems, no H i was detected in any of the 10 sources. Previously published searches, which are overwhelmingly at redshifts of z≲ 1, exhibit a 42 per cent detection rate (31 out of 73 sources), whereas the inclusion of our survey yields a 17 per cent detection rate (two out of 12 sources) at z > 2.5. We therefore believe that our high‐redshift selection is responsible for our exclusive non‐detections, and find that at ultraviolet (UV) luminosities of LUV≳ 1023 W Hz−1, 21‐cm absorption has never been detected. We also find this to not only apply to our targets, but also those at low redshift exhibiting similar luminosities, giving zero detections out of a total of 16 sources over z= 0.24 to 3.8. This is in contrast to the LUV≲ 1023 W Hz−1 sources where there is a near 50 per cent detection rate of 21‐cm absorption. The mix of 21‐cm detections and non‐detections is currently attributed to orientation effects, where according to unified schemes of active galactic nuclei, 21‐cm absorption is more likely to occur in sources designated as radio galaxies (type 2 objects, where the nucleus is viewed through dense obscuring circumnuclear gas) than in quasars (type 1 objects, where we have a direct view to the nucleus). However, due to the exclusively high UV luminosities of our targets it is not clear whether orientation effects alone can wholly account for the distribution, although there exists the possibility that the large luminosities are indicative of a changing demographic of galaxy types. We also find that below luminosities of LUV∼ 1023 W Hz−1, both type 1 and type 2 objects have a 50 per cent likelihood of exhibiting 21‐cm absorption. Finally, we do not detect molecular gas in any of the sources. The lack of H i absorption, combined with the results from Paper I, suggests these sources are not conducive to high molecular abundances.

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“…The smaller the source (and its components) the higher the turnover frequency. An interesting set of sources can be found among the High Frequency Peakers (HFPs; Dallacasa et al 2000;Dallacasa 2003;Orienti 2009), whose radio spectrum is well sampled by currently available instrumentation. Radio spectra at various epochs have been presented by Tinti et al (2005) and Orienti, Dallacasa & Stanghellini (2007) from simultaneous multifrequency VLA observations.…”

Section: Young and Small Radio Sourcesmentioning

confidence: 99%

Does equipartition hold in HFPs?

Dallacasa

Orienti

2009

Astron Nachr

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Equipartition of energy between relativistic particles and magnetic field is known to be consistent with observations in most of the large size (hundreds of kpc) radio galaxies. Here we discuss whether such a property holds in the smallest and youngest radio sources, the High Frequency Peakers (HFPs). A few sources have small components with a turnover frequency occurring at a few GHz and therefore a direct measure of the magnetic field intensity can be derived from the spectral peak assuming the spectral turnover is originated by synchrotron self-absorption. The field strengths computed in this way are generally in excellent agreement with the equipartition fields. However, a few exceptions have been found, in sources with an extra deficit of photons in the optically thick part of the spectrum as a consequence of free-free absorption (FFA).

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High frequency peakers

Cited by 9 publications

References 36 publications

The Compact Radio Structure of Radio-Loud Narrow Line Seyfert 1 Galaxies

The Compact Radio Structure of Radio-Loud Narrow Line Seyfert 1 Galaxies

A survey for redshifted molecular and atomic absorption lines - II. Associated H i, OH and millimetre lines in thez≳ 3 Parkes quarter-Jansky flat-spectrum sample

Does equipartition hold in HFPs?

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