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ABSTRACT We revisit the Quasar Main Sequence (QMS) by investigating the impact of the stellar component from the host galaxy (HG) on the emission line spectra of the active galactic nuclei (AGNs). We first detect spectra with broad emission lines using a line ratio method for a sample of $$\sim$$3000 high SNR ($>$20) black hole mapper objects (part of the fifth phase of the Sloan Digital Sky Survey). We then built the Index diagram, a novel diagnostic tool using the z-corrected spectra, model-free, designed to easily identify spectra with significant stellar HG contributions and to classify the AGN spectra into three categories based on AGN–HG dominance: HG-dominated (HGD), Intermediate (INT), and AGN-dominated (AGND) sources. A colour-z diagram was used to refine the AGN–HG classification. We subtract the stellar contributions from the HGD and INT spectra before modelling the AGN spectrum to extract the QMS parameters. Our QMS reveals that HGD galaxies predominantly occupy the Population B region with no R$$_{\rm {Fe\,{\small II}}}$$, with outliers exhibiting R$$_{\rm {Fe\,{\small II}}}$$  $>$ 1, likely due to HG subtraction residuals and a faint contribution of h$$\beta _{\rm BC}$$. INT and AGND spectra show similar distributions in the Population A region, while in Population B, a tail of AGND sources becomes apparent. Cross-matching with radio, infrared, and X-ray catalogues, we find that the strongest radio emitters are associated with HGD and INT groups. Strong X-ray emitters are found in INT and AGND sources, also occupying the AGN region in the Wide-field Infrared Survey Explorer colour diagram. 

Spectrum analysis at 3 mm of the central region (r≈800 pc) of NGC 4303 showed molecular gas lines of both dense gas tracers (HCN, HNC, HCO+, and C2H) and diffuse gases (13CO and C18O). Molecular gas parameters: H2 mass MH2=(1.75±0.32)×108M☉; radial velocity Vdense=178±60 km s-1, and VCO=151±29 km s-1; HCN luminosity LHCN=(7.38±1.40)×106 K km s-1 pc2; dense gas mass Mdense=(4.7±0.3)×107 M☉, indicating a significant contribution of dense to total molecular gas mass. To explore the AGN nature and central dusty torus of the galaxy, CIGALE was used to fit the integrated spectral energy distribution. Large torus properties are estimated: luminosity LTORUS=(7.1±2.8)×1043 erg s-1 and line of sight inclination of 67±16°, which is consistent with a Type 2 AGN; total infrared luminosity LIR=(3.51± 0.30)×1044 erg s-1; star formation rate SFR=6.0±0.3 M☉ yr-1. A marginal AGN contribution of ≈20% was found. 

ABSTRACT We present ground-based multiband light curves of the AGN Mrk 509, NGC 4151, and NGC 4593 obtained contemporaneously with Swift monitoring. We measure cross-correlation lags relative to Swift UVW2 (1928 Å) and test the standard prediction for disc reprocessing, which assumes a geometrically thin optically thick accretion disc where continuum interband delays follow the relation $$\tau (\lambda) \propto \lambda ^{4/3}$$. For Mrk 509 the 273-d Swift campaign gives well-defined lags that increase with wavelength as $$\tau (\lambda)\propto \lambda ^{2.17\pm 0.2}$$, steeper than the thin-disc prediction, and the optical lags are a factor of $$\sim 5$$ longer than expected for a simple disc-reprocessing model. This ‘disc-size discrepancy’ as well as excess lags in the u and r bands (which include the Balmer continuum and H $$\alpha$$, respectively) suggest a mix of short lags from the disc and longer lags from nebular continuum originating in the broad-line region. The shorter Swift campaigns, 69 d on NGC 4151 and 22 d on NGC 4593, yield less well-defined shorter lags $< 2$ d. The NGC 4593 lags are consistent with $$\tau (\lambda) \propto \lambda ^{4/3}$$ but with uncertainties too large for a strong test. For NGC 4151 the Swift lags match $$\tau (\lambda) \propto \lambda ^{4/3}$$, with a small U-band excess, but the ground-based lags in the r, i, and z bands are significantly shorter than the B and g lags, and also shorter than expected from the thin-disc prediction. The interpretation of this unusual lag spectrum is unclear. Overall these results indicate significant diversity in the $$\tau \!-\!\lambda$$ relation across the optical/UV/NIR, which differs from the more homogeneous behaviour seen in the Swift bands.