A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz

Giacintucci, S.; O’Sullivan, Ewan; Vrtilek, J. M.; David, L. P.; Raychaudhury, Somak; Venturi, T.; Athreya, R.; Clarke, T. E.; Murgia, M.; Mazzotta, P.; Gitti, Myriam; Ponman, T. J.; Ishwara‐Chandra, C. H.; Jones, Christine; Forman, W.

doi:10.1088/0004-637x/732/2/95

Cited by 85 publications

(138 citation statements)

References 131 publications

(192 reference statements)

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“…Thus, it might be possible that the AGN in CT objects are not seen at X-ray frequencies (and therefore their X-ray classification is non-AGN), whereas at radio frequencies the AGN can be detected. Of the four non-AGN candidates studied in HG13 and this work, radio cores are detected in three objects and, in fact, evidence of jet structures are reported in the literature (NGC 4636, Giacintucci et al 2011;NGC 5813, Randall et al 2011;NGC 5846, Filho et al 2004), which suggests that they are AGN. Moreover, in this work UV variability is found for NGC 4636 and NGC 5813, while UV data are not available to study long-term variations in the other two cases.…”

Section: Long-term Variationssupporting

confidence: 61%

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X-ray spectral variability of LINERs selected from the Palomar sample

Hernández-García

González‐Martín

Masegosa

et al. 2014

A&A

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Context. Variability is a general property of active galactic nuclei (AGN). The way in which these changes occur at X-rays is not yet clearly understood. In the particular case of low-ionization nuclear emission line region (LINER) nuclei, variations on the timescales from months to years have been found for some objects, but the main driver of these changes is still debated. Aims. The main purpose of this work is to investigate the X-ray variability in LINERs, including the main driver of these variations, and to search for possible differences between type 1 and 2 objects. Methods. We examined the 18 LINERs in the Palomar sample with data retrieved from the Chandra and/or XMM-Newton archives that correspond to observations gathered at different epochs. All the spectra for the same object were fitted simultaneously to study long-term variations. The nature of the variability patterns were studied by allowing different parameters to vary during the spectral fit. Whenever possible, short-term variations from the analysis of the light curves and long-term UV variability were studied. Results. Short-term variations are not reported in X-rays. Three LINERs are classified as non-AGN candidates in X-rays, all of them are Compton-thick candidates; none of them show variations at these frequencies, and two of them vary in the UV. Long-term X-ray variations were analyzed in 12 out of 15 AGN candidates; about half of them showed variability (7 out of the 12). At UV frequencies, most of the AGN candidates with available data are variable (five out of six). Thus, 13 AGN candidates are analyzed at UV and/or X-rays, ten of which are variable at least in one energy band. None of the three objects that do not vary in X-rays have available UV data. This means that variability on long-timescales is very common in LINERs. These X-ray variations are mainly driven by changes in the nuclear power, while changes in absorptions are found only for NGC 1052. We do not find any difference between type 1 and 2 LINERs, neither in the number of variable cases (three out of five type 1 and four out of seven type 2 LINERs), nor in the nature of the variability pattern. We find indications of an anticorrelation between the slope of the power law, Γ, and the Eddington ratio. Conclusions. LINERs are definitely variable sources irrespective of whether they are classified as optical type 1 or 2. Their BH masses, accretion rates, and variability timescales place them in the same plane as more powerful AGN at X-rays. However, our results suggest that the accretion mechanism in LINERs may be different. UV variations of some type 2 LINERs were found, this could support the hypothesis of a torus that disappears at low luminosities.

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Section: Long-term Variationssupporting

confidence: 61%

“…Recently, Giacintucci et al (2011) found bright jets at radio frequencies. No variations were found at 2 cm with VLA data (Nagar et al 2002).…”

Section: B13 Ngc 4494mentioning

confidence: 99%

X-ray spectral variability of LINERs selected from the Palomar sample

Hernández-García

González‐Martín

Masegosa

et al. 2014

A&A

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“…The existence of aged radio A&A 581, A23 (2015) plasma, detected at frequencies below 1 GHz and associated with X-ray cavities in a number of rich and poor clusters, is interpreted as the signature of repeated radio outbursts from the BCG and strongly supports the AGN feedback picture (e.g. Clarke et al 2005Clarke et al , 2009Fabian et al 2002;Giacintucci et al 2011a;McNamara & Nulsen 2012). …”

Section: Introductionmentioning

confidence: 68%

Brightest cluster galaxies in the extended GMRT radio halo cluster sample

Kale

Venturi

Cassano

et al. 2015

A&A

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Aims. First-ranked galaxies in clusters, usually referred to as brightest cluster galaxies (BCGs), show exceptional properties over the whole electromagnetic spectrum. They are the most massive elliptical galaxies and show the highest probability to be radio loud. Moreover, their special location at the centres of galaxy clusters raises the question of the role of the environment in shaping their radio properties. In the attempt to separate the effect of the galaxy mass and of the environment on their statistical radio properties, we investigate the possible dependence of the occurrence of radio loudness and of the fractional radio luminosity function on the dynamical state of the hosting cluster. Methods. We studied the radio properties of the BCGs in the Extended GMRT Radio Halo Survey (EGRHS), which consists of 65 clusters in the redshift range 0.2-0.4, with X-ray luminosity L X ≥ 5 × 10 44 erg s −1 , and quantitative information on their dynamical state from high-quality Chandra imaging. We obtained a statistical sample of 59 BCGs, which we divided into two classes, depending on whether the dynamical state of the host cluster was merging (M) or relaxed (R). Results. Of the 59 BCGs, 28 are radio loud and 31 are radio quiet. The radio-loud sources are favourably located in relaxed clusters (71%), while the reverse is true for the radio-quiet BCGs, which are mostly located in merging systems (81%). The fractional radio luminosity function for the BCGs in merging and relaxed clusters is different, and it is considerably higher for BCGs in relaxed clusters, where the total fraction of radio loudness reaches almost 90%, to be compared to the ∼30% in merging clusters. For relaxed clusters, we found a positive correlation between the radio power of the BCGs and the strength of the cool core, consistent with previous studies on local samples. Conclusions. Our study suggests that the radio loudness of the BCGs strongly depends on the cluster dynamics; their fraction is considerably higher in relaxed clusters. We compare our results with similar investigations and briefly discuss them in the framework of AGN feedback.

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“…X-ray relaxed nature of fossils may play role in this trend. Giacintucci et al (2011) selected elliptical dominated groups, possess structures in X-ray brightness and temperature distribution or radio morphology, contrary to the fossil groups that they have relaxed and undisturbed X-ray emission.…”

Section: Radio Luminosity In Fossil and Non-fossil Groupsmentioning

confidence: 93%

“…In order to explore the group-scaling behaviour of such fossil and non-fossil systems in relation to the AGN activities, various reference samples have been used. In particular, for a statistical comparison in section 6 we used a non-fossil group sample observed at 610 MHz by Giacintucci et al (2011) and the HI-FLUGCS galaxy cluster sample observed at X-ray (Reiprich & böhringer 2002). In order to investigate the workings of the mechanical heating discussed in section 4.1 we used a galaxy cluster sample as a reference, with mechanical luminosity reported in Birzan et al (2004).…”

Section: Sample Radio Observations and Data Reductionmentioning

confidence: 99%

IGM heating in fossil galaxy groups

Miraghaei

Khosroshahi

Klöckner

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We study intergalactic medium (IGM) heating in a sample of five fossil galaxy groups by using their radio properties at 610 MHz and 1.4 GHz. The power by radio jets introducing mechanical heating for the sampled objects is not sufficient enough to suppress the cooling flow. Therefore, we discussed shock-, vortex heating, and conduction as alternative heating processes. Further, the 1.4 GHz and 610 MHz radio luminosities of fossil groups are compared to a sample of normal galaxy groups of the same radio brightest (BGGs), stellar mass, and total group stellar mass, quantified using the K-band luminosity. It appears that the fossil BGGs are under luminous at 1.4 GHz and 610 MHz for a given BGG stellar mass and luminosity, in comparison to a general population of the groups. In addition, we explore how the bolometric radio luminosity of fossil sample depends on clusters and groups characteristics. Using the HIghest X-ray FLUx Galaxy Cluster Sample (HIFLUGCS) as a control sample we found that the large-scale behaviours of fossil galaxy groups are consistent with their relaxed and virialised nature.

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A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz

Cited by 85 publications

References 131 publications

X-ray spectral variability of LINERs selected from the Palomar sample

X-ray spectral variability of LINERs selected from the Palomar sample

Brightest cluster galaxies in the extended GMRT radio halo cluster sample

IGM heating in fossil galaxy groups

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