arXiv subjects

F. Bonanomi

Publications and source records attributed to F. Bonanomi.

7 recordsLinked to original sources

arXiv2026

Emergence of high-mass stars in complex fiber networks (EMERGE) VI. Turbulence dissipation and the formation of dense fibers

(Abridged) The turbulent cascade naturally generates a hierarchy of filaments within molecular clouds, with fibers suggested to be the first (tran-)sonic components formed out of it. We aim to investigate the diffuse gas kinematics and its interaction with the dense gas composing fibers using HNC as molecular tracer. We use high-resolution (4.5" or 2000au) large-scale ALMA+IRAM-30m mosaics to survey five star-forming regions in Orion, as part of the EMERGE Early ALMA Survey covering a wide range of stellar activity, cloud morphology, and evolutionary stages. We observe our targets in HNC(1-0) as probe of diffuse gas in the regions and compare it to the N2H+(1-0) emission tracing the dense gas. Our high resolution observations reveal that HNC traces lukewarm, diffuse ($\sim5\times10^{21}$ cm$^{-2}$) material around dense fibers. The properties of the diffuse gas appear to be similar across our sample, despite the wide range of different environments. Compared to the quiescent and subsonic gas inside fibers, the diffuse gas is, however, more turbulent ($M_\text{s}=2.9$). Understanding the dissipation process is crucial to mark the transition between the dense subsonic gas and diffuse turbulent material occurs. We investigated the turbulence dissipation through the statistical analysis of the HNC velocity gradients. We identified high-shear regions showing higher gradients with $\nabla V_{lsr}\ge10~\mathrm{km~s^{-1}~pc^{-1}}$ concentrated in small features of 0.1-0.3 pc in size located near the dense gas. These high-shear structures appear to be major contributors of the turbulence dissipation in our targets. Our results suggest that in Orion the transition to coherence occurs at the fiber level, as suggested by the turbulence being effectively dissipated before the formation of cores and during the formation of these first dense structures.

astro-ph.GA↗

arXiv2024

Emergence of high-mass stars in complex fiber networks (EMERGE) V. From filaments to spheroids: the origin of the hub-filament systems

Identified as parsec-size, gas clumps at the junction of multiple filaments, hub-filament systems (HFS) play a crucial role during the formation of young clusters and high-mass stars. These HFS appear nevertheless to be detached from most galactic filaments when compared in the mass-length (M-L) phase-space. We aim to characterize the early evolution of HFS as part of the filamentary description of the interstellar medium. Combining previous scaling relations with new analytic calculations, we created a toy model to explore the different physical regimes described by the M-L diagram. Despite its simplicity, our model accurately reproduces several observational properties reported for filaments and HFS such as their expected typical aspect ratio ($A$), mean surface density ($\Sigma$), and gas accretion rate ($\dot{m}$). Moreover, this model naturally explains the different mass and length regimes populated by filaments and HFS, respectively. Our model predicts a dichotomy between filamentary ($A\geq 3$) and spheroidal ($A<3$) structures connected to the relative importance of their fragmentation, accretion, and collapse timescales. Individual filaments with low accretion rates are dominated by an efficient internal fragmentation. In contrast, the formation of compact HFS at the intersection of filaments triggers a geometric phase-transition leading to the gravitational collapse of these structures at parsec-scales in $\sim$1Myr also inducing higher accretion rates.

astro-ph.GA↗

arXiv2024

Emergence of high-mass stars in complex fiber networks (EMERGE) III. Fiber networks in Orion

The Herschel observations unveiled the complex organisation of the interstellar medium in networks of parsec-scale filaments over the past decade. At the same time, networks of fibers have been recognised describing the gas structures in star-forming regions at sub-parsec scales. We aim to investigate the dense gas organisation prior to the formation of stars in sample of 7 star-forming regions within Orion. This EMERGE Early ALMA Survey includes OMC-1/-2/-3/-4 South, LDN 1641N, NGC 2023, and the Flame Nebula, all surveyed at high spatial resolution (4.5'' or $\sim2000$ au) in N$_2$H$^+$ (1$-$0) using ALMA+IRAM-30m observations. We systematically investigated the star-forming gas spatial distribution, its column density variations, its thermal structure, and its internal motions in a wide range of environments. From the analysis of the gas kinematics, we identified and characterised a total of 152 velocity-coherent fibers in our survey, which appear to be the preferred organisational unit for the dense gas in low-, intermediate- and high-mass star-forming regions alike. Despite the uneven density of fibers within these sub-parsec networks, the masses and lengths of these objects show similar distributions and consistent median values, as well as (trans-)sonic motions, in all of our targets. The comparison between the fiber line masses and virial line masses suggests the majority of these objects to be sub-virial. Those fibers closer to the virial condition, however, also have the most protostars associated to them, proving to be intimately connected to star formation. Finally, the surface density of fibers is linearly correlated with the total dense gas mass throughout roughly one order of magnitude in both parameters. These findings demonstrate how the formation and evolution of fibers networks can explain the current star formation properties of their host region.

astro-ph.GA↗

arXiv2024

Emergence of high-mass stars in complex fiber networks (EMERGE) IV. Environmental dependence of the fiber widths

Despite their variety of scales throughout the interstellar medium, filaments in nearby low-mass clouds show a characteristic width of $\sim$ 0.1 pc from the analysis of {\it Herschel} observations. The origin of this characteristic width, however, has been a matter of intense discussions during the last decade. We explored a possible variation in this typical width with the EMERGE Early ALMA Survey, which includes seven star-forming regions in Orion (OMC-1/-2/-3/-4 South, LDN 1641N, NGC 2023, Flame Nebula). These targets, which exhibit different physical conditions, star formation histories, mass, and density regimes, were homogeneously surveyed at a resolution of $\sim$ 2000 au in N$_2$H$^+$ (1$-$0) with ALMA+IRAM-30m observations. We characterised the column density and temperature radial profiles of the 152 fibers identified in the survey using the automatic fitting routine FilChap. These Orion fibers show a departure from the isothermal condition with significant outward temperature gradients with $\nabla T_\mathrm{K} > 30$ K pc$^{-1}$. They also show a median full width at half maximum ($FWHM$) of $\sim 0.05$ pc, with a corresponding median aspect ratio of $\sim2$. More relevantly, we observe a systematic variation in these fiber $FWHM$ between different regions in our sample, and a direct inverse dependence of these $FWHM$ on their central column density, $N_0$, above $\gtrsim 10^{22}$ cm$^{-2}$. This dependency agrees with the expected $N_0-FWHM$ anti-correlation predicted in previous theoretical studies. Our homogeneous analysis returns the first observational evidence of an intrinsic and systematic variation in the fiber widths across different star-forming regions. While sharing comparable mass, length, and kinematic properties in all of our targets, fibers appear to adjust their $FWHM$ to their density and to the pressure in their host environment.

astro-ph.GA↗

arXiv2024

Emergence of high-mass stars in complex fiber networks (EMERGE) II. The need for data combination in ALMA observations

ALMA's high-resolution images allow to resolve the filamentary structure of the ISM down to few thousand au at kpc distances. We aim to systematically quantify the impact of the interferometric response and the effects of the short-spacing information during the characterization of the ISM structure using ALMA observations. We create a series of continuum ALMA synthetic observations to test the recovery of the observational properties of dense cores and filaments (i.e. intensity peak, radial profile, and width) at different scales. We compare the results obtained with and without different data combination techniques using different ALMA arrays and SD telescopes in simulated data and real observations. Our analysis illustrates the severity of interferometric filtering effects. ALMA-12m alone observations show significant scale-dependent flux losses systematically corrupting (>30%error) all the physical properties inferred in cores and filaments (i.e. column density, mass, and size) before the maximum recoverable scale of the interferometer. These effects are only partially mitigated by the addition of the ALMA ACA-7m array although degrading the telescope PSF. Our results demonstrate only the addition of the ALMA Total Power information allows to recover the true sky emission down to few times the ALMA beamsize with satisfactory accuracy (<10% error). Additional tests demonstrate the emission recovery at all scales is further improved if the 7mTP data are replaced by maps obtained by a larger SD telescope (e.g., IRAM-30m), even if the latter are noisier than expected. These observational biases particularly affect partially resolved targets, becoming critical especially for studies in nearby regions such as Taurus or Orion. Our results demonstrate the need for the use of data combination techniques to accurately characterize the complex physical structure of the ISM in the ALMA era.

astro-ph.GA↗

arXiv2024

Emergence of high-mass stars in complex fiber networks (EMERGE). I. Early ALMA Survey: observations and massive data reduction

(Abridged) Recent molecular surveys have revealed a rich gas organization of sonic-like fibers in all kind of environments prior to the formation of low- and high-mass stars. This paper introduces the EMERGE project aiming to investigate whether complex fiber arrangements could explain the origin of high-mass stars and clusters. We analyzed the EMERGE Early ALMA Survey including 7 star-forming regions in Orion (OMC-1/2/3/4 South, L1641N, NGC2023, and Flame Nebula) homogeneously surveyed in both molecular lines (N$_2$H$^+$ J=1-0, HNC J=1-0, plus HC3N J=10-9) and 3mm-continuum using a combination of interferometric ALMA mosaics and IRAM-30m single-dish (SD) maps. Based on our low-resolution (SD) observations, we describe the global properties of our sample covering a wide range of physical conditions including low-, intermediate, and high-mass star-forming regions in different evolutionary stages. Their comparison with ancillary YSO catalogs denotes N$_2$H$^+$ as the best proxy for the dense, star-forming gas in our targets showing a constant star formation efficiency and a fast time evolution of <1 Myr. While apparently clumpy and filamentary in our SD data, all targets show a much more complex fibrous substructure at the enhanced resolution of our ALMA+IRAM-30m maps. A large number of filamentary features at sub-parsec scales are clearly recognized in the high-density gas traced by N$_2$H$^+$ directly connected to the formation of individual protostars. This complex gas organization appears to extend further into the more diffuse gas traced by HNC. This paper presents the EMERGE Early ALMA survey including a first data release of continuum maps and spectral products for this project to be analysed in future papers of this series. A first look at these results illustrates the need of advanced data combination techniques to investigate the intrinsic multi-scale, gas structure of the ISM.

astro-ph.GA↗

arXiv2023

Another X-ray UFO without a momentum-boosted molecular outflow. ALMA CO(1-0) observations of the galaxy pair IRAS 05054+1718

We present ALMA CO(1-0) observations of the nearby LIRG galaxy pair IRAS05054+1718 with a new analysis of X-ray data collected between 2012 and 2021 using NuSTAR, Swift, and XMM-Newton. The western component of the pair, NED01, hosts a Seyfert 1.9 nucleus launching a powerful X-ray UFO. Our X-ray spectral analysis suggests the UFO could be variable or multi-component in velocity and constrains its momentum flux to $\dot p^{X-ray}_{out} \sim (4\pm2)\times 10^{34}$ gcms$^{-2}$. ALMA CO(1-0) observations include also the eastern component of the pair, a LIRG with no clear evidence for an AGN. We study the CO(1-0) kinematics in the two galaxies using the 3D-BAROLO code. In both sources, we can model the bulk of the CO(1-0) emission with rotating disks and, after subtracting the best-fit models, we detect compact residual emission at S/N=15 within $\sim3$kpc from the centre. A molecular outflow in NED01, if present, cannot be brighter than such residuals, implying an upper limit on its outflow rate of $\dot{M}^{mol}_{out} \lesssim 19\pm14~M_{\odot}~yr^{-1}$ and on its momentum rate of $\dot p^{mol}_{out} \lesssim (2.7\pm2.4) \times 10^{34}$gcms$^{-1}$. Combined with the revised energetics of the X-ray wind, we derive an upper limit on the momentum rate ratio of $\dot{p}^{mol}_{out}/\dot{p}^{X-ray}_{out}<0.67$. We discuss these results in the context of the expectations of AGN feedback models, and we propose the X-ray disk wind in NED01 has not significantly impacted the molecular gas reservoir (yet), and we can constrain its effect to be much smaller than expectations of AGN ''energy-driven'' feedback models. We also consider and discuss the hypothesis of asymmetries of the molecular disk not properly captured by the 3D-BAROLO code. Our results highlight the challenges in testing the predictions of popular AGN disk-wind feedback theories, even with good quality multi-wavelength observations.

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