Molecular gas and nuclear activity in early-type galaxies: any link with radio loudness?

Baldi, Ranieri D.; Giroletti, M.; Capetti, A.; Giovannini, G.; Casasola, V.; Pérez-Torres, M. Á.; Kuno, Nario

doi:10.1051/0004-6361/201425131

Cited by 8 publications

(6 citation statements)

References 64 publications

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“…Excluding NGC 7252 as a source we know to be SF dominated and dividing our galaxies at L 1.4 GHz =10 22 W HZ −1 , we find that 7/14 of the more radio luminous systems are detected in CO (50±14%) compared to 14/32 radio fainter systems (44±12%). This suggests that the presence of molecular gas does not automatically lead to radio-luminous nuclear activity (see also Baldi et al 2015). We also find no correlation between radio power and CO(2-1)/CO(1-0) line ratio, suggesting that AGN have only a limited effect on the excitation of the molecular gas in our BGEs.…”

Section: Gas Mass Vs Radio Luminositymentioning

confidence: 53%

Cold gas in a complete sample of group-dominant early-type galaxies

O’Sullivan

Combes

Salomé

et al. 2018

A&A

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We present IRAM 30m and APEX telescope observations of CO(1-0) and CO(2-1) lines in 36 group-dominant early-type galaxies, completing our molecular gas survey of dominant galaxies in the Complete Local-volume Groups Sample. We detect CO emission in 12 of the galaxies at >4σ significance, with molecular gas masses in the range ∼0.01-6×10 8 M , as well as CO in absorption in the non-dominant group member galaxy NGC 5354. In total 21 of the 53 CLoGS dominant galaxies are detected in CO and we confirm our previous findings that they have low star formation rates (0.01-1M yr −1 ) but short depletion times (<1 Gyr) implying rapid replenishment of their gas reservoirs. Comparing molecular gas mass with radio luminosity, we find that a much higher fraction of our group-dominant galaxies (60±16%) are AGN-dominated than is the case for the general population of ellipticals, but that there is no clear connection between radio luminosity and the molecular gas mass. Using data from the literature, we find that at least 27 of the 53 CLoGS dominant galaxies contain H , comparable to the fraction of nearby non-cluster early type galaxies detected in H and significantly higher that the fraction in the Virgo cluster. We see no correlation between the presence of an X-ray detected intra-group medium and molecular gas in the dominant galaxy, but find that the H -richest galaxies are located in X-ray faint groups. Morphological data from the literature suggests the cold gas component most commonly takes the form of a disk, but many systems show evidence of galaxy-galaxy interactions, indicating that they may have acquired their gas through stripping or mergers. We provide improved molecular gas mass estimates for two galaxies previously identified as being in the centres of cooling flows, NGC 4636 and NGC 5846, and find that they are relatively molecular gas poor compared to our other detected systems.

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Section: Gas Mass Vs Radio Luminositymentioning

confidence: 53%

Cold gas in a complete sample of group-dominant early-type galaxies

O’Sullivan

Combes

Salomé

et al. 2018

A&A

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“…A correlation between dust mass and radio power was found by De Ruiter et al (2002). LERGs with 1.4 GHz radio luminosities P 1.4 > ∼ 10 22 W Hz −1 also contain significantly larger masses of cold molecular gas than radio-weak or radio-silent ETGs (Paper II), but the dependence of dust and gas mass on P 1.4 does not appear to extend to lower radio luminosities (Paper II; Baldi et al 2015).…”

Section: Dust and Molecular Gas In Radio Galaxiesmentioning

confidence: 77%

The AGN fuelling/feedback cycle in nearby radio galaxies I. ALMA observations and early results

Ruffa

Prandoni

Laing

et al. 2019

Monthly Notices of the Royal Astronomical Society

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This is the first paper of a series exploring the multi-frequency properties of a sample of eleven nearby low excitation radio galaxies (LERGs) in the southern sky. We are conducting an extensive study of different galaxy components (stars, warm and cold gas, radio jets) with the aim of improving our understanding of the AGN fuelling/feedback cycle in LERGs. We present ALMA Band 6 12 CO(2-1) and continuum observations of nine sources. Continuum emission from the radio cores was detected in all objects. Six sources also show mm emission from jets on kpc/sub-kpc scales. The jet structures are very similar at mm and cm wavelengths. We conclude that synchrotron emission associated with the radio jets dominates the continuum spectra up to 230 GHz. The 12 CO(2-1) line was detected in emission in six out of nine objects, with molecular gas masses ranging from 2×10 7 to 2×10 10 M . The CO detections show disc-like structures on scales from ≈0.2 to ≈10 kpc. In one case (NGC 3100) the CO disc presents some asymmetries and is disrupted in the direction of the northern radio jet, indicating a possible jet/disc interaction. In IC 4296, CO is detected in absorption against the radio core as well as in emission. In four of the six galaxies with CO detections, the gas rotation axes are roughly parallel to the radio jets in projection; the remaining two cases show large misalignments. In those objects where optical imaging is available, dust and CO appear to be co-spatial.

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“…This is likely connected to the fact that NGC 3998 is located in a region of fairly high galaxy density (Cappellari et al 2011b). CO observations by Baldi et al (2015b) revealed that NGC 3998 hosts molecular gas with an H 2 mass of ∼1.7 × 10 7 M .…”

Section: Overview Of Ngc 3998mentioning

confidence: 99%

A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

Frank

Morganti

Oosterloo

et al. 2016

A&A

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We study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar H i disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ∼10 kpc from the galaxy centre. Remarkably, we find that the inner H i disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar H i disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The "S" shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via "discrete events", suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event.

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Molecular gas and nuclear activity in early-type galaxies: any link with radio loudness?

Cited by 8 publications

References 64 publications

Cold gas in a complete sample of group-dominant early-type galaxies

Cold gas in a complete sample of group-dominant early-type galaxies

The AGN fuelling/feedback cycle in nearby radio galaxies I. ALMA observations and early results

A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

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