LeMMINGs – II. The e-MERLIN legacy survey of nearby galaxies. The deepest radio view of the Palomar sample on parsec scale

Abstract

We present the second data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 177 nearby galaxies from the Palomar sample, observed with the e-MERLIN array, as part of the LeMMINGs (Legacy e-MERLIN Multi-band Imaging of Nearby Galaxy Sample) survey. Together with the 103 targets of the first LeMMINGs data release, this represents a complete sample of 280 local active (LINER and Seyfert) and inactive galaxies (H ii galaxies and Absorption Line Galaxies, ALG). This large program is the deepest radio survey of the local Universe, ≳ 1017.6 W Hz−1, regardless of the host and nuclear type: we detect radio emission ≳0.25 mJy beam−1 for 125/280 galaxies (44.6 per cent) with sizes of typically ≲100 pc. Of those 125, 106 targets show a core which coincides within 1.2 arcsec with the optical nucleus. Although we observed mostly cores, around one third of the detected galaxies features jetted morphologies. The detected radio core luminosities of the sample range between ∼1034 and 1040 erg s−1. LINERs and Seyferts are the most luminous sources, whereas H ii galaxies are the least. LINERs show FR I-like core-brightened radio structures while Seyferts reveal the highest fraction of symmetric morphologies. The majority of H ii galaxies have single radio core or complex extended structures, which probably conceal a nuclear starburst and/or a weak active nucleus (seven of them show clear jets). ALGs, which are typically found in evolved ellipticals, although the least numerous, exhibit on average the most luminous radio structures, similar to LINERs.

The eMERLIN and EVN View of FR 0 Radio Galaxies

“…The large scatter of the correlation, ∼0.27 dex, could be caused by the Doppler boosting, the nuclear variability, and the different data frequencies (particularly sensitive in the case of the steep spectrum). Furthermore, the slope of the established linear correlation is consistent with that found for nearby low-luminosity RL LINERs studied with eMERLIN [43]. However, a study on a large sample of FR 0s at lower radio luminosities is still needed to confirm the existence of this linear regression.…”

“…Since an affinity between the nuclear properties of FR 0s and FR Is has been clearly assessed [64,72,73] and low-power RGs have been found to be the scaled-down version of FR Is (e.g., [28,43,53,99,100]), it is plausible to search for a general connection between the jet and accretion strength of a population of low-and high-power RGs with comparable properties: hosted in massive ETGs and characterized by a LINER spectrum (we excluded the FR II LINERs, because the nature of their central engine and its relation to the FR I LINERs is still not fully understood [11,101,102]). With the purpose of building such a sample of local (z < 0.05) LINER-type RL AGNs, we collected VLBI, VLBA, EVN, and eMERLIN data at 1.4 GHz and 5 GHz available from the literature ([O III] line emission from [44,103]); see Figure 5 for: LINERs from the Palomar sample of nearby galaxies [104] (green circles, from [28,[105][106][107]), which appear as unresolved cores or core-jet structures at JVLA scales in the radio band and were classified as RL by [43]; 3C/FR Is (all LINERs, open upwards triangles, from [107][108][109][110]); and core galaxies (open downward triangles, from [28]), which have LINER spectra and are known to be miniature FR Is [100]. With the inclusion of these RL AGNs in the L core -L [O III] plot, it is evident that the FR 0 data points belong to a broad sequence between the two luminosities correlated on ∼4 order of magnitudes.…”

“…They are: (1) about two-thirds of the all local active galaxies [28,29]; (2) characterized by low-ionization optical forbidden lines [30] whose source of ionization has been debated for decades (low-luminosity version of bright AGNs [31], shocks [32], or stellar photoionization [33,34]); (3) powered by low-accreting radiatively inefficient discs (RIAF) [35] in the case of hosting an active BH [36]. The accretion-powered LINERs tend to host compact radio-louder cores [37][38][39][40], as the BH mass (or galaxy mass) increases (e.g., [13,[41][42][43]). In fact, as LINERs (or in the RL regime, low-excitation radio galaxies (In the optical taxonomy of RL AGNs, RL LINERs are typically named as low-excitation radio galaxies (LERGs), while Seyferts as high-excitation radio galaxies [44,45].…”

The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation

“…Herrera Ruiz et al 2016;Jarvis et al 2019;Hartley et al 2019), and with the presence of radio jets with luminosities down to at least 10 21 W Hz −1 in massive galaxies that do not host quasars (e.g. Sabater et al 2019;Mingo et al 2019;Baldi et al 2021).…”

“…This would not be surprising since such low luminosity radio jets are commonly seen in massive galaxies (although these radio-AGN are not optically classified as quasars; e.g. Heckman & Best 2014;Mingo et al 2019;Baldi et al 2021), with Sabater et al (2019) finding evidence that locally they are essentially always present in the most massive galaxies. Mancuso et al (2017) attempted to explain the abundances of SF-dominated and jet-dominated RQ quasars using a model of in-situ evolution whereby the origin of the dominant radio emission changes as the black hole grows.…”