LeMMINGs III. The e-MERLIN legacy survey of the Palomar sample: exploring the origin of nuclear radio emission in active and inactive galaxies through the [O iii] – radio connection

Abstract

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O iii] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity ($L_{\rm [O\, \small {III}]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm 0.33}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.79\pm 0.30}$. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim 10^{19.8}$ W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local active galaxies.

The eMERLIN and EVN View of FR 0 Radio Galaxies

“…Another outstanding result of this study, which strengthens the connection between FR 0s and FR Is, is the presence of a broad correlation between the pc-scale core luminosities and the [O III] line luminosities, used as a proxy of the AGN strength, established for low-power LINER-like RGs, which encompass FR 0s, FR Is, and low-luminosity RL LINERs in general. This result suggests that RL LINERs, other than sharing the same type of host (massive ETGs with a BH mass > 10 7.5 M ), also share a single type of central engine, able to launch (from low to high power) core-dominated jets [92,99,122] with (from mildly to highly) relativistic speeds. A radiatively inefficient accretion disc is the most plausible engine to account for the low Eddington ratios and low bolometric luminosities of FR 0s and FR Is [53,73,123].…”

“…We calibrated the dataset with the eMERLIN CASA data reduction pipeline [90], which is intended to automate the procedures required in processing and calibrating radio astronomy data from the eMERLIN correlator. After removing the low-level RFIs with the AOFlagger software [91], we also performed a standard calibration procedure by fitting the offsets in delays using the CASA task "fringefit", by calculating the bandpass and phase solutions (see [92] for more details on the eMERLIN pipeline and the comparison with standard AIPS data reduction and imaging). The complex gains (phase and amplitude) were improved with several runs of self-calibration on the gain calibrators and then applied to all the targets.…”

LeMMINGs – IV. The X-ray properties of a statistically complete sample of the nuclei in active and inactive galaxies from the Palomar sample

“…We note that the entire sample includes more galaxies at higher X-ray luminosities which may provide a reason for the steeper gradients and stronger correlation coefficients, but, given the uncertainties in the fits, the entire and Complete sample values agree with one another within ∼1𝜎. Therefore, we do not find a break X-ray-M relation as in the LeMMINGs radio-M 𝐵𝐻 relation (Baldi et al 2018(Baldi et al , 2021b.…”

“…In Figure 8 and Figure 9, we display 400 draws from the fitting process to give a visual guide to the scatter in the correlations. As an additional analysis, we computed the correlation for sources with black hole masses greater than 10 7 M , in order to find show any global difference in the slope at lower masses, in analogy to a break found in the radio LeMMINGs sample (Baldi et al 2018(Baldi et al , 2021b.…”

The Origin of Radio Emission in Black Hole X-ray Binaries

“…We observe a scale-invariant property (BH fundamental plane) of BH activity [47][48][49] among BHXBs (stellar BH with M BH ∼ 3-20M , typically M BH ∼ 10M ) and AGNs (supermassive BH with M BH > 10 6 M ). The timescale of an outburst in BHXBs ranges from days to years, and the M BH scaled up to the timescale of millions of years in AGNs, as suggested from AGN duty cycle (e.g., [50,51]). One exception is the so-called 'changing-look' AGN (e.g., [52]), and its state change timescale can be as low as months.…”