Abstract
The morphology of quiescent galaxies has been found to be correlated with the activity of their central super massive black hole. In this work, we use data from the first data release of the LOFAR Two-Metre Sky Survey (LoTSS DR1) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) to select more than 15 000 quiescent galaxies at z < 0.3 to investigate the connection between radio-loud active galactic nuclei (RLAGNs) and the morphology of their host galaxy. Taking advantage of the depth of LoTSS, we find that the fraction of RLAGNs with L150 MHz > 1021 W Hz−1 at fixed stellar mass, velocity dispersion, or surface mass density does not depend on the galaxy projected axis ratio (q). However, the high-power (L150 MHz > 1023 W Hz−1) RLAGNs are more likely to be found in massive, round galaxies, while the low- and intermediate-power (L150 MHz ≤ 1023 W Hz−1) RLAGNs have similar distributions of q to non-RLAGN galaxies. We argue that our results support the picture that high-power RLAGNs are more easily triggered in galaxies with a merger-rich history, while low-power RLAGNs can be triggered in galaxies growing mainly via secular processes. Our work also supports the idea that the low-luminosity RLAGN may be sufficient for maintenance-mode feedback in low-mass quiescent galaxies with disc-like morphology, which is based on a simple extrapolation from the observed energy balance between cooling and RLAGN-induced cavities in massive clusters. We find no significant difference between the q distributions of RLAGNs likely to be found in clusters and those likely not found in clusters after controlling the radio luminosity and stellar mass of the two samples, indicating that the environment does not significantly influence the morphology–RLAGN correlation.
Highlights
The morphology of quiescent galaxies has been found to be correlated with the activity of their central super massive black hole
We find no significant difference between the q distributions of RLAGNs likely to be found in clusters and those likely not found in clusters after controlling the radio luminosity and stellar mass of the two samples, indicating that the environment does not significantly influence the morphology–RLAGN correlation
We combined the LoTSS DR1 and SDSS DR7 data in the HETDEX region to form a sample of 15934 colour-based quiescent galaxies with 1912 RLAGNs brighter than L150 MHz =
Summary
Our radio sample is based on LoTSS (Shimwell et al 2017), a high-resolution low-frequency (120 to 168 MHz) survey aiming to cover the whole northern hemisphere. We make use of the SED fitting results from Chang et al (2015), who combined SDSS and WISE photometry to make a comprehensive catalogue for galaxies in SDSS This catalogue provides useful information such as stellar mass and star-formation rate for galaxies and 10357 radio sources. We restrict our analysis to galaxies above the SDSS DR7 mass completeness limit, log(Mlimit /M ) = 10.6 + 2.28 log(z/0.1) (Chang et al 2015) This limit is adopted to avoid biasing results by some low-mass high-luminosity sources. The final sample in our following analysis contains 15934 colour-based quiescent galaxies, of which 3661 galaxies are associated with a radio source and 1912 galaxies are hosts of RLAGNs with. 460 have a high probability (>80%) of being associated with a cluster, while 1138 have a probability of less than 50%
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