Compact Steep Spectrum Radio Sources Research Articles

The FLASH pilot survey: an H i absorption search against MRC 1-Jy radio sources

ABSTRACT We report an ASKAP search for associated H i 21-cm absorption against bright radio sources from the Molonglo Reference Catalogue (MRC) 1-Jy sample. The search uses pilot survey data from the ASKAP First Large Absorption Survey in H i (FLASH) covering the redshift range 0.42 < z < 1.00. From a sample of 62 MRC 1-Jy radio galaxies and quasars, we report three new detections of associated H i 21-cm absorption, yielding an overall detection fraction of $1.8\,{{\,\rm per\,cent}}^{+4.0\,{{\,\rm per\,cent}}}_{-1.5\,{{\,\rm per\,cent}}}$. The detected systems comprise two radio galaxies (MRC 2216−281 at z = 0.657 and MRC 0531−237 at z = 0.851) and one quasar (MRC 2156−245 at z = 0.862). The MRC 0531−237 absorption system is the strongest found to date, with a velocity integrated optical depth of $\rm 143.8 \pm 0.4 \ km \ s^{-1}$. All three objects with detected H i 21-cm absorption are peaked-spectrum or compact steep-spectrum (CSS) radio sources. Two of them show strong interplanetary scintillation at 162 MHz, implying that the radio continuum source is smaller than 1 arcsec in size even at low frequencies. Among the class of peaked-spectrum and compact steep-spectrum radio sources, the H i detection fraction is $23\,{{\,\rm per\,cent}}^{+22\,{{\,\rm per\,cent}}}_{-13\,{{\,\rm per\,cent}}}$. All three detections have a high 1.4 GHz radio luminosity, with MRC 0531−237 and MRC 2216−281 having the highest values in the sample, $\rm \gt 27.5 \ W \ Hz^{-1}$. The preponderance of extended radio sources in our sample could partially explain the overall low detection fraction, while the effects of a redshift evolution in gas properties and AGN UV luminosity on the neutral gas absorption still need to be investigated.

Compact Steep Spectrum Radio Sources with Enhanced Star Formation Are Smaller Than 10 kpc

Compact steep spectrum (CSS) radio sources are active galactic nuclei (AGN) that have radio jets propagating only on galactic scales, defined as having projected linear size (LS) of up to 20 kpc. CSS sources are generally hosted by massive early-type galaxies with little ongoing star formation; however, a small fraction are known to have enhanced star formation. Using archival data from the Faint Images of the Radio Sky at Twenty cm survey, the Very Large Array Sky Survey, and the Sloan Digital Sky Survey, we identify a volume-limited sample of 166 CSS sources at z < 0.2 with L 1.4 GHz > 1024 W Hz−1. Comparing the star formation rates and linear sizes of these CSS sources, we find that the ≈14% of CSS sources with specific star formation rates above 0.01 Gyr−1 all have LS < 10 kpc. We discuss the possible mechanisms driving this result, concluding that it is likely the excess star formation in these sources occurred in multiple bursts and ceased prior to the AGN jet being triggered.

Young but fading radio sources: searching for remnants among compact steep-spectrum radio sources

ABSTRACT The incidence of young but fading radio sources provides important information on the life cycle of radio emission in radio-loud active galactic nuclei. Despite its importance for constraining the models of radio source evolution, there are no systematic studies of remnants in complete samples of young radio sources. We report results of the study of 18 compact steep-spectrum (CSS) radio sources, selected from the statistically complete B3-VLA (Very Large Array) CSS sample, characterized by a steep optically thin spectrum (α ≥ 1.0) and no core detection in earlier studies. Our deep multifrequency VLA, pc-scale Very Long Baseline Array, and enhanced Multi Element Remotely Linked Interferometer Network (e-MERLIN) observations allowed us to locate the core component in 10 objects. In three CSS sources, there is no clear evidence of present-time active regions, suggesting that they are likely in a remnant phase. Among sources with core detection, we find three objects that have no clear active regions (hotspots) at the edges of the radio structure, suggesting that the radio emission may have just restarted. Our results support a power-law distribution of the source ages, although the poor statistics prevents us from setting solid constraints on the percentage of remnants and restarted sources in subpopulations of radio sources.

The Energetics of the Central Engine in the Powerful Quasar 3C 298

Abstract The compact steep-spectrum radio source 3C 298 (redshift of 1.44) has the largest 178 MHz luminosity in the Third Cambridge Revised Catalogue (3CR); its radio lobes are among the most luminous in the universe. The plasma state of the radio lobes is modeled with the aid of interferometric radio observations (in particular, the new Low Frequency Array observation and archival MERLIN data) and archival single-station data. It is estimated that the long-term time-averaged jet power required to fill these lobes with leptonic plasma is Q ¯ ≈ 1.28 ± 0.51 × 10 47 erg s − 1 , rivaling the largest time-averaged jet powers from any quasar. Supporting this notion of extraordinary jet power is a 0.5–10 keV luminosity of ≈ 5.2 × 1046 erg s−1, comparable to luminous blazars, yet there is no other indication of strong relativistic beaming. We combine two new high signal-to-noise ratio optical spectroscopic observations from the Hobby-Eberly Telescope with archival Hubble Space Telescope, Two Micron All Sky Survey, and Galaxy Evolutionary Explorer data to compute a bolometric luminosity from the accretion flow of L bol ≈ 1.55 ± 0.15 × 1047 erg s−1. The ratio, Q ¯ / L bol ≈ 1 , is the approximate upper limit for quasars. Characteristic of a large Q ¯ / L bol , we find an extreme-ultraviolet (EUV) spectrum that is very steep (the “EUV deficit” of powerful radio quasars relative to radio-quiet quasars), and this weak ionizing continuum is likely a contributing factor to the relatively small equivalent widths of the broad emission lines in this quasar.

Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

We present the first Fermi Large Area Telescope (LAT) catalog of long-term $\gamma$-ray transient sources (1FLT). This comprises sources that were detected on monthly time intervals during the first decade of Fermi-LAT operations. The monthly time scale allows us to identify transient and variable sources that were not yet reported in other Fermi-LAT catalogs. The monthly datasets were analyzed using a wavelet-based source detection algorithm that provided the candidate new transient sources. The search was limited to the extragalactic regions of the sky to avoid the dominance of the Galactic diffuse emission at low Galactic latitudes. The transient candidates were then analyzed using the standard Fermi-LAT Maximum Likelihood analysis method. All sources detected with a statistical significance above 4$\sigma$ in at least one monthly bin were listed in the final catalog. The 1FLT catalog contains 142 transient $\gamma$-ray sources that are not included in the 4FGL-DR2 catalog. Many of these sources (102) have been confidently associated with Active Galactic Nuclei (AGN): 24 are associated with Flat Spectrum Radio Quasars; 1 with a BL Lac object; 70 with Blazars of Uncertain Type; 3 with Radio Galaxies; 1 with a Compact Steep Spectrum radio source; 1 with a Steep Spectrum Radio Quasar; 2 with AGN of other types. The remaining 40 sources have no candidate counterparts at other wavelengths. The median $\gamma$-ray spectral index of the 1FLT-AGN sources is softer than that reported in the latest Fermi-LAT AGN general catalog. This result is consistent with the hypothesis that detection of the softest $\gamma$-ray emitters is less efficient when the data are integrated over year-long intervals.

The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C 82

Abstract 3C 82 at a redshift of 2.87 is the most distant 3C (Third Cambridge Catalogue) quasar. Thus, it is a strong candidate to have the most-luminous radio lobes in the universe. 3C 82 belongs to the class of compact steep-spectrum radio sources. We use single-dish and interferometric radio observations in order to model the plasma state of these powerful radio lobes. It is estimated that the long-term time-averaged jet power required to fill these lobes with leptonic plasma is , among the largest time-averaged jet powers from a quasar. Positing protonic lobes is not tenable as they would require two orders of magnitude more mass transport to the lobes than was accreted to the central black hole during their formation. The first high signal-to-noise optical spectroscopic observation obtained of this object indicates that there is a powerful high-ionization broad-line wind with a kinetic power of ∼1045 erg s−1 and a velocity of ∼0.01c. We also estimate from the broad lines in 2018 and the UV continuum in three epochs spread out over three decades that the accretion flow bolometric luminosity is L bol ≈ 3.2–5.8 × 1046 erg s−1. The ratio of is perhaps the largest of any known quasar. Extremely powerful jets tend to strongly suppress powerful winds of ionized baryonic matter. Consequently, 3C 82 provides a unique laboratory for studying the dynamical limits of the central engine of outflow initiation in quasars.

Investigation on young radio AGNs based on SDSS spectroscopy

ABSTRACT The gigahertz peaked spectrum (GPS) sources, compact steep spectrum (CSS) radio sources, and high-frequency peaker (HFP) radio sources are thought to be young radio active galactic nuclei (AGNs) at the early stage of AGN evolution. We investigated the optical properties of the largest sample of 126 young radio AGNs based on the spectra in SDSS DR12. We find that the black hole masses MBH range from 107.32 to 109.84$\rm M_{\odot }$ and the Eddington ratios Redd vary from 10−4.93 to 100.37, suggesting that young radio AGNs have various accretion activities and not all are accreting at high accretion rate. Our young radio sources generally follow the evolutionary trend towards large-scale radio galaxies with increasing linear size and decreasing accretion rate in the radio power–linear size diagram. The radio properties of low-luminosity young radio AGNs with low Redd are discussed. The line width of [O iii] λ5007 core (σ[O iii]) is found to be a good surrogate of stellar velocity dispersion σ*. The radio luminosity $L_{\rm 5\, GHz}$ correlates strongly with [O iii] core luminosity L[O iii], suggesting that radio activity and accretion are closely related in young radio sources. We find one object that can be defined as a narrow-line Seyfert 1 galaxy, representing a population of young AGNs with both young jet and early accretion activity. The optical variabilities of 15 quasars with multi-epoch spectroscopy were investigated. Our results show that the optical variability in young AGN quasars presents low variations ($\leqslant \! 60{{\ \rm per\ cent}}$) similar to the normal radio-quiet quasars.

Searching for signs of jet-driven negative feedback in the nearby radio galaxy UGC 05771

ABSTRACT Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and [Fe ii] emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a ‘stalling wind’. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source’s total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources.

Feedback from low-luminosity radio galaxies: B2 0258+35

Low-luminosity radio-loud active galactic nuclei (AGN) are of importance in studies concerning feedback from radio AGN since a dominant fraction of AGN belong to this class. We report high-resolution Very Large Array (VLA) and European VLBI Network (EVN) observations of H I 21 cm absorption from a young, compact steep-spectrum radio source, B2 0258+35, nested in the early-type galaxy NGC 1167, which contains a 160 kpc H I disc. Our VLA and EVN H I absorption observations, modelling, and comparison with molecular gas data suggest that the cold gas in the centre of NGC 1167 is very turbulent (with a velocity dispersion of ∼90 km s−1) and that this turbulence is induced by the interaction of the jets with the interstellar medium (ISM). Furthermore, the ionised gas in the galaxy shows evidence of shock heating at a few kpc from the radio source. These findings support the results from numerical simulations of radio jets expanding into a clumpy gas disc, which predict that the radio jets in this case percolate through the gas disc and drive shocks into the ISM at distances much larger than their physical extent. These results expand the number of low-luminosity radio sources found to impact the surrounding medium, thereby highlighting the possible relevance of these AGN for feedback.

Relativistic jet feedback – II. Relationship to gigahertz peak spectrum and compact steep spectrum radio galaxies

We propose that Gigahertz Peak Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources are the signposts of relativistic jet feedback in evolving galaxies. Our simulations of relativistic jets interacting with a warm, inhomogeneous medium, utilize cloud densities and velocity dispersions in the range derived from optical observations, show that free-free absorption can account for the $\sim \rm GHz$ peak frequencies and low frequency power laws inferred from the radio observations. These new computational models replace the power-law model for the free-free optical depth in the \citep{bicknell97a} model by a more fundamental model involving disrupted log-normal distributions of warm gas. One feature of our new models is that at early stages, the low frequency spectrum is steep but progressively flattens as a result of a broader distribution of optical depths, suggesting that the steep low frequency spectra discovered by \citet{callingham17a} may possibly be attributed to young sources. We also investigate the inverse correlation between peak frequency and size and find that the initial location on this correlation is determined by the average density of the warm ISM. The simulated sources track this correlation initially but eventually fall below it, indicating the need for a more extended ISM than presently modelled. GPS and CSS sources can potentially provide new insights into the phenomenon of AGN feedback since their peak frequencies and spectra are indicative of the density, turbulent structure and distribution of gas in the host galaxy.

Letter from the Editor

Welcome to volume 338, our 196th year of continuous appearance. The past and previous years were a bit furious for us and had brought a number of editorial changes. The first one is that Astronomische Nachrichten/Astronomical Notes (AN) now appears only electronically. Already with last year's volume, we formally declared farewell to glossy paper. We believe we are in good company with this decision. Note that print-on-demand is still possible and is already being requested by several guest editors for special issues. Then, we had to say goodbye to our associate managing editor Professor Detlef Schönberner, former head of the stellar physics section at AIP, and now in real retirement. He had been our editorial hawk eye, spotting any kind of typo with a single look. Many thanks for all the years with AN, and may the force be with you. Electronic publishing also opens a number of advantages, both for authors as well as readers. Firstly, because we switched the internal article layout to a more modern platform, we can now generate and post articles in hyper text markup language (HTML). It allows porting an article to cell phone and tablet screens while at the same time also providing better access for search engines. Secondly, an (individual) Early View platform was implemented so that our individual research articles go online as soon as they are accepted by the editor and typeset. Publishing an article does not have to wait until an issue is full anymore. This should be useful for authors who, for example, urgently need a digital object identifier (DOI) for a funding proposal. By the way, this will also be true for proceedings articles. Thirdly, a new interface for the Author–Editor–Referee interaction will be implemented during this year. While in the past, most articles were simply submitted by e-mail and then inserted into a local managing system at AIP, we will provide the option of direct submission within the ScholarOne Manuscript system. Among its advantages is that an author can follow the status of the submission on the web, for example, is it already at the referee and, if yes, for how long. Submission is still possible through the old system or through e-mail, but the intention is to transfer to ScholarOne within 2017. So stay tuned. Looking back at 2016, the content of volume number 337 was also an unusual one. Five special issues were our publishing record so far, albeit not intended because two issues slipped into this volume from the previous and the forthcoming year. It started with issue 1–2, which collected the contributions of the Fifth Workshop on “Compact Steep Spectrum and GHz-peaked Spectrum Radio Sources,” held in Rimini, Italy. The workshop “The Extremes of Black Hole Accretion” was organized by the XMM-Newton Science Operations Centre and appeared in issue 4–5. The calendar year 2016—sadly—also saw the last AN issue of the series of the fall meetings of the German Astronomische Gesellschaft. Its volume Reviews in Modern Astronomy 28 covered the topic “From the First Quasars to Life-Bearing Planets—From Accretion Physics to Astrobiology” in issue 7. The mechanisms of the formation and evolution of the Milky Way was the central topic of the 592 Heraeus Symposium “Reconstructing the Milky Way's History: Spectroscopic Surveys, Asteroseismology, and Chemodynamical Models.” It appeared as issue 8–9. Finally, the last issue in 337, issue 10, covered the 12th Potsdam Thinkshop on “The Dynamic Sun—Exploring the Many Facets of Solar Eruptive Events.” Besides these special issues and their many individual articles, 24 independent research articles appeared. We will see in the next years how well these were received and cited in the community. As in the past, publication in AN continues to be free of charge. Also, all articles of the first issue of each year can be downloaded free of charge, as can all articles labeled ”Editor's Choice,” which often are additionally featured with a color image on the front cover. Naturally, AN is linked to all major net-based libraries and can be found in the SAO/NASA ADS library.

THE GAMMA-RAY-EMITTING QUASAR 0202+149: A CSS REVISITED

ABSTRACT PKS 0202+149 is a low-power radio source with blazar-like, γ-ray active galactic nucleus (AGN) characteristics. We investigate its properties and classification in relation to its γ-ray characteristics. This source shows a hint of low-frequency turnover at about 200 MHz. Radio imaging data of 0202+149 at different frequencies show differing morphologies on both kiloparsec (kpc) and parsec (pc) scales. The overall source shows a triple structure of a core and double lobes with a total projected size of ∼1.3 kpc. The compact source structure of 0202+149 is reminiscent of a compact steep spectrum (CSS) source. At pc scales, a core-jet structure extends ∼25 pc (in projection) at a position angle perpendicular to the kpc-scale structure. The curved pc-scale structure with a jet and inner lobe suggests that the CSS nuclear activity has recently re-started, although its power has been decreasing, while the kpc-scale lobes are relics of earlier activity. A maximum apparent superluminal motion of is detected in the jet components, indicating a highly relativistic jet flow. The brightness temperature of the core is lower than the average value found for highly beamed, γ-ray AGNs, indicating a lower radio power and a relatively lower Doppler boosting factor. The CSS radio classification indicates that blazar-like γ-ray properties can also be manifested in low-power CSS radio sources with the appropriate jet and beaming properties.

THE RADIO/X-RAY CORRELATION AND BLACK HOLE FUNDAMENTAL PLANE FOR YOUNG RADIO SOURCES: IMPLICATIONS FOR X-RAY ORIGIN AND ACCRETION MODE

ABSTRACT We find that the young radio sources (gigahertz-peaked spectrum and compact steep spectrum radio sources) follow in the radio/X-ray correlation with b = 0.61 &PlusMinus; 0.07 ?> ( L R &prop; L X b ?> ), and the fundamental plane of black hole activity with the form log L R = 0.58 &minus; 0.03 &plus; 0.03 log L X &plus; 0.42 &minus; 0.07 &plus; 0.09 log M BH &plus; 13.83 &minus; 0.97 &plus; 0.91 ?> and the intrinsic scatter &sgr; = 0.29 ?> . The flatter coefficient between radio and X-ray bands denies the jet origin of the X-ray emission in these types of sources. Meanwhile, the higher ratio of X-ray luminosity to Eddington luminosity ( L X / L Edd ?> ) suggests that the X-ray emission is produced by the hot corona coupling with the standard thin disk. The deviation with the radiative efficient fundamental plane proposed by Dong et al. is mainly due to the extended radio emission in young radio sources. This fundamental plane manifests that even the kiloparsec-scaled radio emission has a tight connection with the accretion process, and could be suitable for the radio-loud active galactic nuclei whose radio and X-ray emission are dominated by the extended jets and the radiative efficient accretion flow, respectively. Otherwise, the high-excitation galaxies and low-excitation galaxies do not have obvious distinctions in the radio/X-ray correlation and the fundamental plane.

The infrared properties of the GPS and CSS radio sources

AbstractI review the results of three Spitzer studies of GHz‐Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio galaxies. The luminosity of the IR continuum and the high ionization lines confirm that some GPS/CSS can have central engines which are similar to those of the extended powerful radio sources. This is consistent with the hypothesis that some GPS/CSS can evolve to become the large‐scale sources. Warm H2 is common in the GPS/CSS sources consistent with feedback via jet‐ISM interaction. The GPS/CSS seem to have higher star formation rates than typical (2JY + 3CRR) radio sources. This should be confirmed with a larger sample. If compact sources interact with dense, clumpy star forming clouds and if the interaction with the dense medium sufficiently enhances the radio power, these star forming galaxies with enhanced radio emission will be selected for the current bright samples of GPS and CSS sources. This will increase the number of GPS and CSS sources which are observed to be forming stars. If radio sources have longer lives and/or star formation is more common in large radio galaxies, the need for a new population of star forming compact sources with enhanced radio emission is reduced. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

GPS/CSS radio sources and their relation to other AGN

AbstractWe are entering a new era of sensitive, large‐area and multi‐frequency radio surveys that will allow us to identify Gigahertz‐Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources over a wide range in radio luminosity and study them within the context of the overall radio‐source populations to which they belong. “Classical” GPS/CSS objects are extremely luminous radio sources with a compact double morphology, commonly thought to represent the earliest stages in the life cycle of powerful radio galaxies (e.g. O'Dea 1998). It is now becoming easier to identify GPS/CSS candidates with much lower radio luminosity – particularly in the nearby Universe. These less powerful objects, with typical 1.4 GHz radio luminosities of 1023 to 1025 W Hz–1, include peaked‐spectrum radio sources with a core‐jet morphology on parsec scales as well as high‐frequency GPS‐like peaked components embedded within lower‐frequency extended emission. In the latter case, the presence of a young GPS component may not be evident from low‐frequency data alone. Many radio galaxies in the local Universe have a compact (FR‐0) morphology, and appear to lack extended radio emission on kiloparsec scales. The relationship of these FR‐0 objects to the classical GPS/CSS radio sources remains unclear – some of them may represent short‐lived episodes of AGN activity that will not lead to an extended FR‐1 or FR‐2 radio galaxy. Future wide‐band radio surveys will shed more light on this – such surveys should ideally be coordinated to cover the full frequency range from 100 MHz to 100 GHz in order to sample all stages of GPS/CSS evolution in an unbiased way. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Phenomenological model for the evolution of radio galaxies such as Cygnus A

A phenomenological model for the evolution of classical radio galaxies such as Cygnus A is presented. An activity cycle of the host galaxy in the radio begins with the birth of radio jets, which correspond to shocks on scales ∼1 pc (the radio galaxy B0108+388). In the following stage of the evolution, the radio emission comes predominantly from formations on scales of 10–100 pc, whose physical parameters are close to those of the hot spots of Cygnus A (this corresponds to GHz-peaked spectrum radio sources). Further, the hot spots create radio lobes on scales of 103–104 pc (compact steep-spectrum radio sources). The fully formed radio galaxies have radio jets, hot spots, and giant radio lobes; the direction of the jets can vary in a discrete steps with time, creating new hot spots and inflating the radio lobes (as in Cygnus A). In the final stage of the evolutionary cycle, first the radio jets disappear, then the hot spots, and finally the radio lobes (similar to the giant radio galaxies DA 240 and 3C 236). A large fraction of radio galaxies with repeating activity cycles is observed. The close connection between Cygnus A-type radio galaxies and optical quasars is noted, as well as similarity in the cosmological evolution of powerful radio galaxies and optical quasars.

On the Dependence of Spectral Turnover on Linear Size of Compact Steep Spectrum Radio Sources

Frequency peak/linear size (ν_p-D) relation gives the strongest correlation among all the currently observable physical properties of Compact Steep Spectrum Sources (CSSs). This strong correlation suggests that the spectral turnover constitutes a characteristic signature of dense gases around the CSS sources which may be used to constrain physical mechanisms that govern the dynamical evolution of CSS sources. We have therefore, carried out statistical analyses to ascertain whether the observed ν_p-D correlation is real or an artifact arising from a possible spectral turnover/radio luminosity (ν_p-P) and/or linear size/radio luminosity (D-P) correlations. Our results show only a marginally significant ν_p-P correlation (correlation coefficient, r≈0.3) and apparently little or no D-P correlation. This suggests that the mechanism for the spectral turnover lies mainly in the source size according to the relation, ν_p~D^(-0.7), with correlation coefficient, r≈-0.9.

SDSS J143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources?

We present SDSSJ143244.91+301435.3, a new case of radio-loud narrow line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4GHz=2.1x10^25 W Hz^-1) and large radioloudness parameter (R1.4=600+/-100). The radio source is compact with a linear size below ~1.4 kpc but, contrary to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (alpha=0.93) and not supporting a 'blazar-like' nature. Both the small mass of the central super-massive black-hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2x10^7 Msun and 0.27, respectively, with a formal error of ~0.4 dex on both quantities) are typical of the class of NLS1. Through a modeling of the spectral energy distribution of the source we have found that the galaxy hosting SDSSJ143244.91+301435.3 is undergoing a quite intense star-formation (SFR=50 Msun y^-1) which, however, is expected to contribute only marginally (~1 per cent) to the observed radio emission. The radio properties of SDSSJ143244.91+301435.3 are remarkably similar to those of compact steep spectrum (CSS) radio sources, a class of AGN mostly composed by young radio galaxies. This may suggest a direct link between these two classes of AGN, with the CSS sources possibly representing the misaligned version (the so-called parent population) of RL NLS1 showing blazar characteristics.

First X-ray observations of low-power compact steep spectrum sources

We report first X-ray Chandra observations of a sample of seven low luminosity compact (LLC) sources. They belong to a class of young compact steep spectrum (CSS) radio sources. Four of them have been detected, the other three have upper limit estimations for X-ray flux, one CSS galaxy is associated with an X-ray cluster. We have used the new observations together with the observational data for known strong CSS and gigahertz-peaked spectrum (GPS) objects and large scale FRIs and FRIIs to study the relation between morphology, X-ray properties and excitation modes in radio-loud AGNs. We found that: (1) The low power objects fit well to the already established X-ray - radio luminosity correlation for AGNs and occupy the space among, weaker in the X-rays, FRI objects. (2) The high excitation galaxies (HEG) and low excitation galaxies (LEG) occupy distinct locus in the radio/X-ray luminosity plane, notwithstanding their evolutionary stage. This is in agreement with the postulated different origin of the X-ray emission in these two group of objects. (3) We have tested the AGN evolution models by comparing the radio/X-ray luminosity ratio with the size of the sources, and indirectly, with their age. We conclude that the division for two different X-ray emission modes, namely originate in the base of the relativistic jet (FRIs) or in the accretion disk (FRIIs) is already present among the younger compact AGNs. (4) Finally, we found that the CSS sources are less obscured than the more compact GPSs in X-rays. However, the anti-correlation between X-ray column density and radio size does not hold for the whole sample of GPS and CSS objects.

AN X-RAY COOLING-CORE CLUSTER SURROUNDING A LOW-POWER COMPACT STEEP SPECTRUM RADIO SOURCE 1321+045

We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z=0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium (ISM) dominated by AGN-photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radio activity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1+/-8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3 sigma level out to ~60 arcsec (~240 kpc). We obtain the best fit beta model parameters of the surface brightness profile of beta=0.58+/-0.2 and a core radius of 9.4^{+1.1}_{-0.9} arcsec. The average temperature of the cluster is equal to kT=4.4^{+0.5}_{-0.3} keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L_(0.5-2 keV)=3x10^{44} erg s^{-1} and mass 1.5x10^{14} M_sun.