UV Lines Research Articles

Influence of Finishing Process Parameters of HDF Boards on Selected Properties of Coatings in Modern UV Lines and Their Relation to Energy Consumption

This study analyzes the influence of energy generated by emitters on the adhesive properties of varnish coatings in multilayer UV systems. The experimental material, in the form of a cell board finished with UV varnish products, was prepared on a prototype line under the conditions of Borne Furniture in Gorzów Wielkopolski. The roughness and wettability were measured using a OneAttension tensiometer integrated with a topographic module, taking into account the Wenzel coefficient. The adhesion of the examined systems was verified using the PositiTest AT-A automatic pull-off device. Energy consumption by the prototype production line was compared to the standard line, utilizing mercury emitters and mercury emitters with added gallium. Energy consumption was calculated for selected variants. The influence of the Wenzel coefficient on the wettability angle was observed. Significant differences between contact angles (CA and CAc) were noted for coatings formed with sealers (stages I and II). The largest discrepancies, reaching up to 30 degrees, were recorded at the lowest UVA and UVV doses of 26 mJ/cm2. In adhesion tests, values below 1 MPa were obtained. Insufficient energy doses in the curing process of UV systems led to delamination between the coatings. Five variants were selected where delamination within the substrate predominated (˃90% A) and were characterized by the lowest energy consumption in the processes. Topographic images helped identify the presence of various surface microstructures at different stages of the production cycle. The greatest energy savings, up to 50%, were achieved in stages III and IV of the technological process.

Ultraviolet line structuring of large solar wafers

AbstractUltrashort‐pulsed lasers are ideal for material processing by welding, marking, and cutting. Scanning systems are crucial for large substrates. We introduce a novel UV line structuring method using deformable mirror technology and freeform optics. This approach aims to improve processing times on large substrates, especially for M12 solar wafer processing. By using a freeform lens and a Zwobbel deformable mirror, we achieve extended processing fields and high scan frequencies. The paper explores optical designs, their robust optomechanical implementation for prototyping, and setup characterization.

JWST NIRSpec Spectroscopy of the Remarkable Bright Galaxy GHZ2/GLASS-z12 at Redshift 12.34

We spectroscopically confirm the M UV = −20.5 mag galaxy GHZ2/GLASS-z12 to be at redshift z = 12.34. The source was selected via NIRCam photometry in GLASS-JWST Early Release Science data, providing the first evidence of a surprising abundance of bright galaxies at z ≳ 10. The NIRSpec PRISM spectrum shows detections of N iv, C iv, He ii, O iii, C iii, O ii, and Ne iii lines and the first detection at high redshift of the O iii Bowen fluorescence line at 3133 Å rest frame. The prominent C iv line with rest-frame equivalent width (EW) ≈ 46 Å puts GHZ2 in the category of extreme C iv emitters. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne iv]/[N iv] ratio favoring a stellar origin of the ionizing photons. We discuss a possible scenario in which the high ionizing output is due to low-metallicity stars forming in a dense environment. We estimate a metallicity ≲0.1 Z/Z ⊙, a high ionization parameter log U > −2, a N/O abundance 4–5 times the solar value, and a subsolar C/O ratio similar to the recently discovered class of nitrogen-enhanced objects. Considering its abundance patterns and the high stellar mass density (104 M ⊙ pc−2), GHZ2 is an ideal formation site for the progenitors of today's globular clusters. The remarkable brightness of GHZ2 makes it a “Rosetta stone” for understanding the physics of galaxy formation within just 360 Myr after the Big Bang.

Dual Role of Accretion Disk Winds as X-Ray Obscurers and UV Line Absorbers in AGN

X-ray obscuration of active galactic nuclei (AGNs) is considered in the context of ionized winds of stratified structure launched from accretion disks. We argue that a Compton-thick layer of a large-scale disk wind can obscure continuum X-rays and also lead to broad UV absorption, such as in the blue wing of C iv; the former originates from the inner wind and the latter from the outer wind, as a dual role. Motivated by a number of lines of observational evidence showing strong AGN obscuration phenomena in Seyfert 1 AGNs such as NGC 5548, we demonstrate in this work, by utilizing a physically motivated wind model coupled to post-process radiative transfer calculations, that an extended disk wind under certain physical conditions (e.g., morphology and density) could naturally cause a sufficient obscuration qualitatively consistent with UV/X-ray observations. Predicted UV/X-ray correlation is also presented as a consequence of variable spatial size of the wind in this scenario.

Quasar 3C 47: Extreme Population B jetted source with double-peaked profiles

Context. An optically thick, geometrically thin accretion disk (AD) around a supermassive black hole might contribute to broad-line emission in type 1 active galactic nuclei (AGN). However, the emission line profiles are most often not immediately consistent with the profiles expected from a rotating disk. The extent to which an AD in AGN contributes to the broad Balmer lines and high-ionization UV lines in radio-loud (RL) AGN needs to be investigated. Aims. This work aims to determine whether the AD can account for the double-peaked profiles observed in the Balmer lines (Hβ, Hα), near-UV (MgIIλ2800), and high-ionization UV lines (C IVλ1549, CIII]λ1909) of the extremely jetted quasar 3C 47. Methods. The low ionization lines (LILs) (Hβ, Hα, and Mg IIλ2800) were analyzed using a relativistic Keplerian AD model. Fits were carried out following Bayesian and multicomponent nonlinear approaches. The profiles of prototypical high ionization lines (HILs) were also modeled by the contribution of the AD, along with fairly symmetric additional components. Results. The LIL profiles of 3C 47 agree very well with a relativistic Keplerian AD model. The disk emission is constrained between ≈102 and ≈103 gravitational radii, with a viewing angle of ≈ 30 degrees. Conclusions. The study provides convincing direct observational evidence for the presence of an AD and explains that the HIL profiles are due to disk and failed-wind contributions. The agreement between the observed profiles of the LILs and the model is remarkable. The main alternative, a double broad-line region associated with a binary black hole, is found to be less favored than the disk model for the quasar 3C 47.

First Detection of Outflowing Gas in the Outskirts of the Broad-line Region in 1H 0707−495* *Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), the US National Science Foundation's NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State

We use near-infrared spectroscopy covering simultaneously the zJHK bands to look for outflowing gas from the nuclear environment of 1H 0707−495 taking advantage that this region is dominated by low-ionization broad-line region lines, most of them isolated. We detect broad components in H i, Fe ii, and O i, at rest to the systemic velocity, displaying FWHM values of ∼500 km s−1, consistent with its classification as a narrow-line Seyfert 1 active galactic nucleus. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ∼826 km s−1. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H 0707−495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow-line region owing to the observation of a blueshifted component in the forbidden line of [S iii] λ9531.

The Weakness of Soft X-Ray Intensity: Possible Physical Reason for Weak-line Quasars

Weak-line quasars (WLQs) are a notable group of active galactic nuclei (AGNs) that show unusually weak UV lines even though their optical-UV continuum shapes are similar to those of typical quasars. The physical mechanism for WLQs is an unsolved puzzle in the AGN unified model. We explore the properties of UV emission lines by performing extensive photoionization calculations based on Cloudy simulations with different spectral energy distributions (SEDs) of AGNs. The AGN continua are built from several observational empirical correlations, where the blackbody emission from the cold disk, the power-law emission from the hot corona, and a soft X-ray excess component are considered. We find that the equivalent width (EW) of C iv from our models is systematically lower than observational values if the component of soft X-ray excess is neglected. The EW will increase several times and is roughly consistent with the observations after considering the soft X-ray excess component as constrained from normal type I AGNs. We find that the UV lines are weak for QSOs with quite large black hole mass (e.g., M BH > 109 M ⊙) and weak soft X-ray emission due to the deficit of ionizing photons. As an example, we present the strength of C iv based on the multiband SEDs for three nearby weak-line AGNs, where the weaker soft X-ray emission normally predicts the weaker lines.

AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817*

Abstract An intensive reverberation mapping campaign of the Seyfert 1 galaxy Mrk 817 using the Cosmic Origins Spectrograph on the Hubble Space Telescope revealed significant variations in the response of broad UV emission lines to fluctuations in the continuum emission. The response of the prominent UV emission lines changes over an ∼60 day duration, resulting in distinctly different time lags in the various segments of the light curve over the 14 month observing campaign. One-dimensional echo-mapping models fit these variations if a slowly varying background is included for each emission line. These variations are more evident in the C iv light curve, which is the line least affected by intrinsic absorption in Mrk 817 and least blended with neighboring emission lines. We identify five temporal windows with a distinct emission-line response, and measure their corresponding time delays, which range from 2 to 13 days. These temporal windows are plausibly linked to changes in the UV and X-ray obscuration occurring during these same intervals. The shortest time lags occur during periods with diminishing obscuration, whereas the longest lags occur during periods with rising obscuration. We propose that the obscuring outflow shields the broad UV lines from the ionizing continuum. The resulting change in the spectral energy distribution of the ionizing continuum, as seen by clouds at a range of distances from the nucleus, is responsible for the changes in the line response.

First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548

Multiwavelength spectroscopy of NGC 5548 revealed remarkable changes due to the presence of an obscuring wind from the accretion disk. This broadened our understanding of obscuration and outflows in active galactic nuclei. Swift monitoring of NGC 5548 shows that over the last 10 yr, the obscuration has gradually declined. This provides a valuable opportunity for analyses that have not been feasible before because of too much obscuration. The lowered obscuration, together with the high-energy spectral coverage of Chandra HETG, facilitates the first study of X-ray absorption lines in the obscured state. The comparison of the lines (Mg xi, Mg xii, Si xiii, and Si xiv) between the new and historical spectra reveals interesting changes, most notably the He-like absorption being significantly diminished in 2022. Our study finds that the changes are caused by an increase in both the ionization parameter and the column density of the warm-absorber outflow in the obscured state. This is contrary to the shielding scenario that is evident in the appearance of the UV lines, where the inner obscuring wind shields outflows that are farther out, thus lowering their ionization. The X-ray absorption lines in the HETG spectra appear to be unaffected by the obscuration. The results suggest that the shielding is complex because various components of the ionized outflow are affected differently. We explore various possibilities for the variability behavior of the X-ray absorption lines and find that the orbital motion of a clumpy ionized outflow traversing our line of sight is the most likely explanation.

CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs* *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch of reionization (z > 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called “UV–BPT diagrams”—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (e.g., gas-phase metallicity, ionization parameter, carbon abundance, and stellar age). We find that the combination of C iii] λ λ1907,9 He ii λ1640 and O iii] λ1666 can be a powerful tool to separate between SF, shocks, and AGN at subsolar metallicities. We also confirm that alternative diagrams without O iii] λ1666 still allow us to define an SF-locus, with some caveats. Diagrams including C iv λ λ1548,51 should be taken with caution given the complexity of this doublet profile. Finally, we present a discussion detailing the ISM conditions required to detect UV emission lines, visible only in low gas-phase metallicity (12 + log(O/H) ≲ 8.3) and high ionization parameter (log(U) ≳ −2.5) environments. Overall, CLASSY and our UV toolkit will be crucial in interpreting the spectra of the earliest galaxies that JWST is currently revealing.

A HITRAN-formatted UV line list of S2-containing transitions involving X3 Σg-, B3 Σu-, and B″ 3 Πu electronic states

ABSTRACT The sulfur dimer (S2) is an important molecular constituent in cometary atmospheres and volcanic plumes on Jupiter’s moon Io. It is also expected to play an important role in the photochemistry of exoplanets. The ultraviolet (UV) spectrum of S2 contains transitions between vibronic levels above and below the dissociation limit, giving rise to a distinctive spectral signature. Using spectroscopic information from the literature, and the spectral simulation program PGOPHER, a UV line list of S2 is provided. This line list includes the primary $B\, ^{3}\Sigma ^{-}_{u}-X\, ^{3}\Sigma ^{-}_{g}$ (v′ = 0–27, v″ = 0–10) electronic transition, where vibrational bands with v′≥10 are pre-dissociated. Intensities have been calculated from existing experimental and theoretical oscillator strengths, and semi-empirical strengths for the pre-dissociated bands of S2 have been derived from comparisons with experimental cross-sections. The S2 line list also includes the $B^{\prime \prime }\, ^{3}\Pi _{u}-X\, ^{3}\Sigma ^{-}_{g}$ (v′ = 0–19, v″ = 0–10) vibronic bands due to the strong interaction with the B state. In summary, we present the new HITRAN-formatted S2 line list and its validation against existing laboratory spectra. The extensive line list covers the spectral range 21 700–41 300 cm−1 (∼242–461 nm) and can be used for modelling both absorption and emission.

Constraining the driving mechanism of galaxy-scale winds with emission line spectra

AbstractUsing hydrodynamic simulations and photoionization calculations, we demonstrate that quasar emission line spectra contain information on the driving mechanism of galaxy-scale outflows. Outflows driven by a hot shocked bubble are expected to exhibit LINER-like optical line ratios, while outflows driven by radiation pressure are expected to exhibit Seyfert-like line ratios. Driving by radiation pressure also has a distinct signature in the narrow UV lines, which is detected in an HST-COS spectrum of a nearby quasar hosting a large-scale wind.

AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble Space Telescope UV continuum light curves, we measure interband continuum lags, τ(λ), that increase with increasing wavelength roughly following τ(λ) ∝ λ 4/3, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve—the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad-line region gas that sees an absorbed ionizing continuum.

Extreme Red-wing Enhancements of UV Lines during the 2022 March 30 X1.3 Solar Flare

Here, we present the study of a compact emission source during an X1.3 flare on 2022 March 30. Within a ∼41 s period (17:34:48 UT to 17:35:29 UT), Interface Region Imaging Spectrograph observations show spectral lines of Mg ii, C ii, and Si iv with extremely broadened, asymmetric red wings. This source of interest (SOI) is compact, ∼1.″6, and is located in the wake of a passing ribbon. Two methods were applied to measure the Doppler velocities associated with these red wings: spectral moments and multi-Gaussian fits. The spectral-moments method considers the averaged shift of the lines, which are 85, 125, and 115 km s−1 for the Mg ii, C ii, and Si iv lines respectively. The red-most Gaussian fit suggests a Doppler velocity up to ∼160 km s−1 in all of the three lines. Downward mass motions with such high speeds are very atypical, with most chromospheric downflows in flares on the order 10–100 km s−1. Furthermore, extreme-UV (EUV) emission is strong within flaring loops connecting two flare ribbons located mainly to the east of the central flare region. The EUV loops that connect the SOI and its counterpart source in the opposite field are much less brightened, indicating that the density and/or temperature is comparatively low. These observations suggest a very fast downflowing plasma in the transition region and upper chromosphere, which decelerates rapidly since there is no equivalently strong shift of the O I chromospheric lines. This unusual observation presents a challenge that models of the solar atmosphere’s response to flares must be able to explain.

Shedding far-ultraviolet light on the donor star and evolutionary state of the neutron-star LMXB Swift J1858.6−0814

ABSTRACT The evolution of accreting X-ray binary systems is closely coupled to the properties of their donor stars. Consequently, we can constrain the evolutionary track a system is by establishing the nature of its donor. Here, we present far-ultraviolet (far-UV) spectroscopy of the transient neutron-star low-mass X-ray binary J1858 in different accretion states (low-hard, high-hard, and soft). All of these spectra exhibit anomalous N v, C iv, Si iv, and He ii lines, suggesting that its donor star has undergone CNO processing. We also determine the donor’s effective temperature, Td ≃ 5700 K, and radius, Rd ≃ 1.7 R⊙, based on photometric observations obtained during quiescence. Lastly, we leverage the transient nature of the system to set an upper limit of $\dot{M}_{\rm acc} \lesssim 10^{-8.5}~{\rm M}_{\odot }~\mathrm{ yr}^{-1}$ on the present-day mass-transfer rate. Combining these with the orbital period of the system, Porb = 21.3 h, we search for viable evolution paths. The initial donor masses in the allowed solutions span the range 1 M⊙ ≲ Md,i ≲ 3.5 M⊙. All but the lowest masses in this range are consistent with the strong CNO-processing signature in the UV line ratios. The present-day donor mass in the permitted tracks are 0.5 M⊙ ≲ Md,obs ≲ 1.3 M⊙, higher than suggested by eclipse modelling. Since Porb is close to the so-called bifurcation period, both converging and diverging binary tracks are permitted. If the former is confirmed, J1858 will end its life as an ultracompact system with a substellar donor.

Accurate systemic redshifts and outflow speeds for extremely red quasars (ERQs)

ABSTRACT Extremely Red Quasars (ERQs) are thought to represent a brief episode of young quasar and galactic evolution characterized by rapid outflows and obscured growth due to dusty environments. We use new redshift measurements from CO and narrow Ly α emission-lines to better constrain outflow velocities from previous line measurements. We present sample of 82 ERQs, and the analysis confirms that ERQs have a higher incidence of large C iv blueshifts, accompanied by large Rest Equivalent Width (REW) and narrower line Full Width at Half-Maximum (FWHM) than blue quasars. We find that strong blueshifts (>2000 km s−1) are present in 12/54 (22.2 per cent) of ERQs with the most robust redshift indicators. At least 4 out of 15 ERQs in the sample also have blueshifts in their H β and low-ionization ultraviolet lines ranging from −500 to −1500 km s−1. ERQs with strong C iv blueshifts are substantially offset in C iv REW and FWHM from typical blue quasars in the same velocity range. ERQs have average values of REW = 124 Å and FWHM = 5274 km s−1, while blue quasars have REW = 24 Å and FWHM = 6973 km s−1. The extreme nature of the outflows in ERQs might explain some of their other spectral properties, such as the large C iv REWs and peculiar wingless profiles owing to more extended broad-line regions participating in outflows. The physical reasons for the extreme outflow properties of ERQs are unclear; however, larger Eddington ratios and/or softer ionizing spectra incident on the outflow gas cannot be ruled out.

Late-time Hubble Space Telescope Observations of AT 2018cow. I. Further Constraints on the Fading Prompt Emission and Thermal Properties 50–60 days Post-discovery

The exact nature of the luminous fast blue optical transient AT 2018cow is still debated. In this first of a two-paper series, we present a detailed analysis of three Hubble Space Telescope (HST) observations of AT 2018cow covering ∼50–60 days post-discovery in combination with other observations throughout the first two months and derive significantly improved constraints of the late thermal properties. By modeling the spectral energy distributions (SEDs), we confirm that the UV–optical emission over 50–60 days was still a smooth blackbody (i.e., optically thick) with a high temperature (T BB ∼ 15,000 K) and small radius (R BB ≲ 1000 R ⊙). Additionally, we report for the first time a break in the bolometric light curve: the thermal luminosity initially declined at a rate of L BB ∝ t −2.40 but faded much faster at t −3.06 after day 13. Reexamining possible late-time power sources, we disfavor significant contributions from radioactive decay based on the required 56Ni mass and lack of UV line blanketing in the HST SEDs. We argue that the commonly proposed interaction with circumstellar material may face significant challenges in explaining the late thermal properties, particularly the effects of the optical depth. Alternatively, we find that continuous outflow/wind driven by a central engine can still reasonably explain the combination of a receding photosphere, optically thick and rapidly fading emission, and intermediate-width lines. However, the rapid fading may have further implications on the power output and structure of the system. Our findings may support the hypothesis that AT 2018cow and other “Cow-like transients” are powered mainly by accretion onto a central engine.

Evidence of a Massive Stellar Disruption in the X-Ray Spectrum of ASASSN-14li

The proximity and duration of the tidal disruption event ASASSN-14li led to the discovery of narrow, blueshifted absorption lines in X-rays and UV. The gas seen in X-ray absorption is consistent with bound material close to the apocenter of elliptical orbital paths, or with a disk wind similar to those seen in Seyfert-1 active galactic nuclei. We present a new analysis of the deepest high-resolution XMM-Newton and Chandra spectra of ASASSN-14li. Driven by the relative strengths of He-like and H-like charge states, the data require [N/C] ≥ 2.4, in qualitative agreement with UV spectral results. Flows of the kind seen in the X-ray spectrum of ASASSN-14li were not clearly predicted in simulations of TDEs; this left open the possibility that the observed absorption might be tied to gas released in prior active galactic nucleus (AGN) activity. However, the abundance pattern revealed in this analysis points to a single star rather than a standard AGN accretion flow comprised of myriad gas contributions. The simplest explanation of the data is likely that a moderately massive star (M ≳ 3 M ⊙) with significant CNO processing was disrupted. An alternative explanation is that a lower mass star was disrupted that had previously been stripped of its envelope. We discuss the strengths and limitations of our analysis and these interpretations.

Expanding the inventory of spectral lines used to trace atmospheric escape in exoplanets

Escaping exoplanet atmospheres have been observed as deep transit signatures in a few specific spectral lines. Detections have been made in the hydrogen Ly-αline, the metastable helium line at 10 830 Å, and some UV lines of metallic species. Observational challenges, unexpected nondetections, and model degeneracies have generally made it difficult to draw definitive conclusions about the escape process for individual planets. Expanding on the suite of spectral tracers used may help to mitigate these challenges. We present a new framework for modeling the transmission spectrum of hydrodynamically escaping atmospheres. We predict far UV to near infrared spectra for systems with different planet and stellar types and identify new lines that can potentially be used to study their upper atmospheres. Measuring the radius in the atmosphere at which the strongest lines form puts them into context within the upper atmospheric structure. Targeting a set of complementary spectral lines for the same planet will help us to better constrain the outflow properties.

PENELLOPE

Context. Observing the spatial distribution and excitation processes of atomic and molecular gas in the inner regions (<20 au) of young (<10 Myr) protoplanetary disks helps us to understand the conditions for the formation and evolution of planetary systems. Aims. In the framework of the PENELLOPE and ULLYSES projects, we aim to characterize the atomic and molecular component of protoplanetary disks in a sample of 11 classical T Tauri stars of the Orion OB1 and σ-Orionis associations. Methods. We analyzed the flux-calibrated optical forbidden lines and the fluorescent ultraviolet H2 progressions using spectra acquired with ESPRESSO at VLT, UVES at VLT, and HST-COS. Line morphologies were characterized through Gaussian decomposition. We then focused on the properties of the narrow low-velocity (full width half maximum <40 km s−1 and |υp| < 30 km s−1) component (NLVC) of the [O I] 630 nm line and compared them with those of the UV-H2 lines. Results. We found that the [O I]630 NLVC and the UV-H2 lines are strongly correlated in terms of peak velocities, full width at half maximum values, and luminosity. Assuming that the line width is dominated by Keplerian broadening, the [O I]630 NLVC originates from a disk region between 0.5 and 3.5 au, while that of UV-H2 originates in a region from 0.05 to 1 au. The luminosities of [O I]630 NLVC and UV-H2 correlate with an accretion luminosity with a similar slope, as well as with the luminosity of the C IV154.8, 155 nm doublet. We discuss such correlations in the framework of the currently suggested excitation processes for the [O I]630 NLVC. Conclusions. Our results can be interpreted in a scenario in which the [O I]630 NLVC and UV-H2 have a common disk origin with a partially overlapped radial extension. We also suggest that the excitation of the [O I] NLVC is mainly induced by stellar far-ultraviolet continuum photons, than being of mostly thermal origin. This study demonstrates the potential of contemporaneous wide-band highresolution spectroscopy in linking different tracers of protoplanetary disks.