arXiv subjects

I. O. Izviekova

Publications and source records attributed to I. O. Izviekova.

7 recordsLinked to original sources

arXiv2026

Milky Way Near Twins (MWNeTs). I. A Hierarchical Framework for Identifying Candidate Evolutionary Counterparts of the Milky Way

Searches for Milky Way analogues traditionally rely on a limited set of present-day global properties. However, galaxies with similar morphology, stellar mass, star-formation rate, luminosity, and bulge-to-total ratio may have experienced substantially different assembly, secular, nuclear, and environmental histories. We introduce Milky Way Near Twins (MWNeTs) as galaxies resembling the Milky Way (MW) in their present-day properties and exhibiting observational signatures consistent with broadly similar evolutionary pathways. We aim to extend parameter-based searches towards evolutionary similarity. We propose seven stages: local environment, isolation criterion, and cosmic-web context; morphological and structural constraints; a MW-compatible nuclear state; global spectrophotometric and dynamical constraints; panchromatic spectral-energy-distribution similarity; rotation-curve similarity; and evolutionary fingerprints and fossil tracers. Each stage adds physically motivated constraints, progressively refining the candidate population and strengthening its assessment. For the first time, we formulate MWNeTs as a physically motivated class and establish a hierarchy explicitly distinguishing present-day compatibility from evidence for evolutionary similarity. A companion paper presents the observational application to NGC~3521, NGC~2903, UGC~11487, and CGCG~047-026. The framework is inherently iterative: the MW provides the reference, while near twins offer external laboratories for investigating aspects of Galactic formation and evolution inaccessible from our internal viewpoint. It connects Galactic astronomy, extragalactic astronomy, and cosmology through a comparative approach to testing broadly similar evolutionary pathways.

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arXiv2026

The 2MIG isolated AGNs -- 4. Linking hot-dust reverberation to spectroscopically predicted BLR scales in IC~5287 and Mrk~845

We investigate the relation between directly measured hot-dust reverberation scales and spectroscopically predicted broad-line region (BLR) scales in the isolated Seyfert galaxies IC~5287 and Mrk~845 (MCG+09-25-022), combining ZTF optical light curves, WISE/NEOWISE monitoring, and archival SDSS spectroscopy. Both nuclei show BWB optical variability, RWB MIR behaviour, and delayed MIR responses consistent with circumnuclear dust reprocessing. For IC~5287, interpolated cross-correlation function analysis with flux-randomisation/random-subset-selection uncertainties yields a rest-frame W1 delay of $106_{-39}^{+24}$~d, corresponding to $0.089_{-0.033}^{+0.020}$~pc. The median W2 response occurs at a longer delay, but the lag distributions overlap substantially. The SDSS decomposition reveals strong host dilution and BLR reddening, $E(B-V)_{\rm BLR}=0.612_{-0.066}^{+0.067}$~mag. Applying the same colour excess to the AGN continuum as an illustrative scenario increases the predicted H$β$ BLR lag from approximately 4.8 to 11.7~d and reduces the dust-to-predicted-BLR radius ratios from approximately 20--25 to 8--10. For Mrk~845, transfer-function modelling gives a rest-frame W1 delay of $157_{-8}^{+19}$~d, corresponding to $0.132_{-0.007}^{+0.016}$~pc. Its W2 response occurs at a longer delay, with $P(τ_{\rm W2}>τ_{\rm W1})=0.963$, supporting wavelength-dependent hot-dust structure. The SDSS spectrum shows more moderate BLR reddening, $E(B-V)_{\rm BLR}=0.197_{-0.039}^{+0.046}$~mag. The comparatively large dust-to-predicted-BLR radius ratios in both galaxies therefore primarily reflect the spectroscopically predicted BLR scales. These results emphasise the need to distinguish directly measured dust reverberation radii from BLR radii inferred from single-epoch spectroscopy when interpreting the BLR--dust hierarchy.

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arXiv2026

Revealing a multi-zone circumnuclear dust response in UGC~11487 through phase-resolved WISE W1--W2 diagnostics

Mid-infrared (MIR) flares provide a direct probe of dust reprocessing in obscured tidal disruption event (TDE) candidates when the primary optical or ultraviolet flare is weak, missed, or strongly attenuated. We present a phase-resolved analysis of the WISE/NEOWISE W1-W2 evolution of the MIR-selected TDE candidate UGC 11487/WTP14adeqka over 2014-2024. We combine timing, colour, and flux diagnostics with phenomenological modelling, hydrodynamically motivated clumpy dust-echo calculations, and an aperture-matched ultraviolet-to-radio spectral energy distribution of the host. The decade-long flare shows a delayed and broader W2 response, colour hysteresis, and cooling from approximately 900 K to 500-600 K. Positive-fluence centroids yield a preferred delay of $224 +/- 45$ d, corresponding to $0.188 +/- 0.038$ pc. The effective infrared luminosity peaks at approximately $3 x 10^{43}$ erg s$^{-1}$, and the integrated infrared energy is $(2.9-3.8) x 10^{51}$ erg. A single self-similar MIR response is strongly disfavoured, with Delta BIC = 281.7, while the preferred compact description is a two-component phenomenological model. Representative hydro-clumpy calculations reproduce the empirical diagnostics in a structured, multi-zone dust-response scenario. The host is a moderately star-forming isolated barred disc without a dominant persistent active galactic nucleus component. These results support an obscured TDE-like accretion transient reprocessed by structured circumnuclear dust and show that phase-resolved WISE diagnostics can recover characteristic sub-parsec response scales in obscured accretion-powered nuclear transients.

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arXiv2026

The 2MIG isolated AGNs. 3. Optical--IR variability and dust reverberation in the NLSy1 galaxies Mrk~42 and Mrk~493

This work presents the first dedicated optical--mid-infrared time-domain variability and dust-reverberation analysis of the isolated NLSy1 galaxies Mrk 42 and Mrk 493. We combine ZTF optical light curves, WISE mid-infrared monitoring, archival Swift and SDSS data, and high-cadence IAC80 optical observations. Using colour--magnitude relations, flux--flux analysis, and interpolated cross-correlation functions, we trace variable optical continuum and delayed dust response. Both galaxies show positive optical--MIR lags consistent with dust reverberation. For Mrk 493, we measure an observed-frame g--W1 lag of $τ_{\rm obs}=79.4\pm2.2$ d, corresponding to $R_{\rm dust}(W1)\simeq0.0648$ pc. For Mrk 42, the corresponding lag is $τ_{\rm obs}=39.1\pm2.6$ d, giving $R_{\rm dust}(W1)\simeq0.0320$ pc. These lags provide optical--MIR dust-reverberation radii and BLR--dust scale comparisons for both objects; the resulting $R_{\rm dust}/R_{\rm BLR}$ ratios are $\simeq6.8$ for Mrk 493 and $\sim6$--7 for Mrk 42. For Mrk 42, we derive the first host-subtracted AGN continuum luminosity at 5100 Å from SDSS spectral decomposition, giving a self-consistent BLR--dust comparison on an AGN-only luminosity basis. Both galaxies have similar radial hierarchies but different colour behaviour: Mrk 493 shows significant optical and MIR bluer-when-brighter trends, whereas Mrk 42 shows strong optical but weak MIR colour variability. We also identify and analyse a major optical flare in Mrk 42 with four internal maxima spaced by 45--47 d. We interpret this signal as quasi-periodic substructure within a broader accretion-driven flare, rather than as a strictly coherent periodic process. These results indicate that, even in dynamically isolated environments, the variability of low-mass, high-accretion-rate AGNs is governed mainly by the intrinsic state of the accretion flow and its coupling to circumnuclear dust.

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arXiv2026

NGC 3521 as the Milky Way near twin: spectral energy distribution from UV to radio decameter ranges

Milky Way analogues (MWAs) are usually selected from structural and kinematic properties, but robust SED-based similarity criteria are limited by heterogeneous photometry and incomplete wavelength coverage. We present a homogeneous, aperture-photometry SED of the Milky Way near-twin NGC~3521 from the ultraviolet to the radio decameter range. Fluxes are measured within a fixed elliptical isophotal aperture using GALEX, SDSS, WISE, Spitzer/MIPS, Herschel/PACS+SPIRE, and VLA data, and supplemented by meter/decameter constraints. We report new observations obtained in Jan-Feb 2022 with the Ukrainian T-shape radio telescope and derive, for the first time, an upper limit in the 24--32~MHz band. The UV-to-decameter SED (27 points) is modelled with \textsc{CIGALE}, including a dedicated low-frequency radio prescription (\texttt{radio_extra}) that accounts for emission and absorption effects. Using ZTF and NEOWISE data (2014--2025), we detect genuine nuclear variability; optical trends at $\sim2^{\prime\prime}$ primarily trace the compact nucleus, while NEOWISE variability reflects a mix of nuclear changes and warm-dust emission within the larger aperture. The preferred fit yields $M_\star \simeq 6.0\times10^{10},M_\odot$, ${\rm SFR}\simeq1.65,M_\odot,{\rm yr}^{-1}$, $M_{\rm dust}\simeq1.3\times10^{8},M_\odot$, and an effective dust temperature of $\sim23$~K. The decameter constraint gives $S_{28,{\rm MHz}}<11.22$~Jy, consistent with expectations for a Milky Way-like system placed at 10.7~Mpc. We conclude that an integrated, homogeneous SED, especially below 100~MHz, provides a complementary diagnostic for identifying and validating MWAs and for interpreting how Milky Way properties would appear to an external observer.

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arXiv2026

NGC3521 as the Milky Way analogue: spectral energy distributon from UV to Radio and photometric variability

We studied the multiwavelength properties of NGC 3521, the Milky Way galaxy-twin, from UV- to radio, exploring the data from GALEX for UV-, SDSS for optical, 2MASS, WISE, MIPS (Spitzer) and PACS, SPIRE (Herschel) for IR-, and NRAO VLA for radio ranges. To obtain the spectral energy distribution (SED), we exploited the CIGALE software and constructed SEDs without (model A) and with (model B) AGN module. The type of nuclear activity of NGC 3521 is confirmed as the LINER. We also present the results of the photometric data processing. Exploring the ZTF observations in 2018-2024, we found, for the first time, a weak photometric variability of the nuclear activity, where the correlation between g-r color indices and g-magnitude for long-term timescale shows a BWB trend (bluer-when-brighter) with a Pearson coefficient r(g-r)=0.56, which is a medium correlation. To detect the variability of NGC 3521 during the day (IDV), we provided observations using a Zeiss-600 telescope with an aperture size of 8" at the Terskol observatory. The data obtained in the R-filter with an exposure of 90 sec for three hours on Feb 11, 2022, serve in favor of a trend towards an increase in brightness with the amplitude of variability of 0.04 +- 0.001 mag. According to the results of the simulations, the best fit to the observed SED is provided by model A, which considers the contribution to the radiation from all galaxy components, assuming that the galaxy nucleus is inactive. Within this model, we derived the stellar mass M$_{star}$ = 2.13 * 10$^{10} M_{Sun}$, the dust mass M$_{dust}$ = 8.45 * 10$^{7} M_{Sun}$, and the star formation rate SFR = 1.76 $M_{Sun}$ * yr$^{-1}$ with $χ^{2}$/d.o.f = 1.8. Also, based on the HIPASS radio data, we estimated the mass of neutral hydrogen to be M$_{HI}$ = 1.3 * 10$^{10} M_{Sun}$, which is an order of magnitude greater than the mass of the stellar component.

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arXiv2025

Search for the potential electromagnetic counterparts of neutrino events in SDSS galaxies at z<0.1

Identification of electromagnetic emission in coincidence with high-energy neutrinos is fundamentally important for multimessenger astronomy. Such observations are essential for constraining source localization, determining the source type, and understanding emission mechanisms. Typically, they require following up a neutrino alert (IceCube issues two alert streams: Gold, with at least 50 percent probability of astrophysical origin, and Bronze, with at least 30 percent probability) with an electromagnetic facility, primarily in X-ray and gamma-ray bands. Another approach involves electromagnetic monitoring of hot spots in the IceCube skymap, i.e., positions exceeding the instrument sensitivity. An alternative method consists in performing correlation analysis across available neutrino events and source catalogs. We searched for spatial coincidence between galaxies from SDSS and high-energy neutrino events. The analysis includes IceCube Gold alerts and neutrino-electromagnetic coincidence events from AMON (Astrophysical Multimessenger Observatory Network), identified through the end of September 2025. We examined galaxies from the morphological catalog at redshifts 0.02 to 0.1, which contains 315,776 SDSS DR9 objects with absolute stellar magnitudes in the range from -24 to -13 in the r band. Among 59 IceCube Gold alerts, we found three with only one galaxy (SDSS J231231.52+033415.1) within the 50 percent containment radius. Among 24 neutrino-electromagnetic coincidence events, three more contain only one galaxy (SDSS J220711.14+122535.9) within the same radius. These six galaxies represent the most promising candidates for potential host galaxies of neutrino sources. We summarize their available multiwavelength data and the ZTF light curves obtained from 2018 to 2025.

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