Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202452208
N. Narechania, R. Keppens, A. ud-Doula, N. Moens, J. Sundqvist
Context. Radiation plays a significant role in solar and astrophysical environments, as it may constitute a sizable fraction of the energy density, momentum flux, and total pressure. Modeling the dynamic interaction between radiation and magnetized plasmas in such environments is an intricate and computationally costly task.Aims. The goal of this work is to demonstrate the capabilities of the open-source parallel, block-adaptive computational framework MPI-AMRVAC in solving equations of radiation-magnetohydrodynamics (RMHD) and to present benchmark test cases relevant for radiation-dominated magnetized plasmas.Methods. We combined the existing magnetohydrodynamics (MHD) and flux-limited diffusion (FLD) radiative-hydrodynamics physics modules to solve the equations of RMHD on block-adaptive finite volume Cartesian meshes in any dimensionality.Results. We introduce and validate several benchmark test cases, such as steady radiative MHD shocks, radiation-damped linear MHD waves, radiation-modified Riemann problems, and a multi-dimensional radiative magnetoconvection case. We recall the basic governing Rankine-Hugoniot relations for shocks and the dispersion relation for linear MHD waves in the presence of optically thick radiation fields where the diffusion limit is reached. The RMHD system allows for eight linear wave types, where the classical seven-wave MHD picture (entropy and three wave pairs for slow, Alfvén and fast) is augmented with a radiative diffusion mode.Conclusions. The MPI-AMRVAC code now has the capability to perform multidimensional RMHD simulations with mesh adaptation, making it well suited for larger scientific applications studying magnetized matter-radiation interactions in solar and stellar interiors and atmospheres.
{"title":"Radiation-magnetohydrodynamics with MPI-AMRVAC using flux-limited diffusion","authors":"N. Narechania, R. Keppens, A. ud-Doula, N. Moens, J. Sundqvist","doi":"10.1051/0004-6361/202452208","DOIUrl":"https://doi.org/10.1051/0004-6361/202452208","url":null,"abstract":"<i>Context.<i/> Radiation plays a significant role in solar and astrophysical environments, as it may constitute a sizable fraction of the energy density, momentum flux, and total pressure. Modeling the dynamic interaction between radiation and magnetized plasmas in such environments is an intricate and computationally costly task.<i>Aims.<i/> The goal of this work is to demonstrate the capabilities of the open-source parallel, block-adaptive computational framework MPI-AMRVAC in solving equations of radiation-magnetohydrodynamics (RMHD) and to present benchmark test cases relevant for radiation-dominated magnetized plasmas.<i>Methods.<i/> We combined the existing magnetohydrodynamics (MHD) and flux-limited diffusion (FLD) radiative-hydrodynamics physics modules to solve the equations of RMHD on block-adaptive finite volume Cartesian meshes in any dimensionality.<i>Results.<i/> We introduce and validate several benchmark test cases, such as steady radiative MHD shocks, radiation-damped linear MHD waves, radiation-modified Riemann problems, and a multi-dimensional radiative magnetoconvection case. We recall the basic governing Rankine-Hugoniot relations for shocks and the dispersion relation for linear MHD waves in the presence of optically thick radiation fields where the diffusion limit is reached. The RMHD system allows for eight linear wave types, where the classical seven-wave MHD picture (entropy and three wave pairs for slow, Alfvén and fast) is augmented with a radiative diffusion mode.<i>Conclusions.<i/> The MPI-AMRVAC code now has the capability to perform multidimensional RMHD simulations with mesh adaptation, making it well suited for larger scientific applications studying magnetized matter-radiation interactions in solar and stellar interiors and atmospheres.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202553667
Tatsuya Yoshida, Eric Gaidos
The demographics of sub-Jovian planets around low-mass stars is dominated by populations of sub-Neptunes and super-Earths, distinguished by the presence or absence of envelopes of volatiles with a low molecular weight, that is, H2, He, and H2O. The current paradigm is that sub-Neptunes on close-in orbits evolve into super-Earths via atmospheric escape driven by high-energy stellar irradiation. We used an integrated hydrodynamic-radiation-chemical network model of the outflow to demonstrate that this escape is modulated by the abundance of H2O, which is an efficient infrared coolant. Increasing the H2O/H2 at the base of the flow induces a 1 dex decline in the escape rate, with definitive consequences for the retention of envelopes over Gyr. We show that saturation limits on H2O in the upper atmospheres of temperate sub-Neptunes could explain the paradoxical observation that these objects disappear more rapidly than their counterparts closer to their host stars. We also propose that the scarcity of sub-Neptunes around very low-mass stars could be related to the water-poor chemistry of their antecedent protoplanetary disks. Observations of atmospheric H2O by JWST as well as searches for atmospheric escape from younger planets using H and He lines could test these predictions.
{"title":"Water-cooled (sub)-Neptunes get better gas mileage","authors":"Tatsuya Yoshida, Eric Gaidos","doi":"10.1051/0004-6361/202553667","DOIUrl":"https://doi.org/10.1051/0004-6361/202553667","url":null,"abstract":"The demographics of sub-Jovian planets around low-mass stars is dominated by populations of sub-Neptunes and super-Earths, distinguished by the presence or absence of envelopes of volatiles with a low molecular weight, that is, H<sub>2<sub/>, He, and H<sub>2<sub/>O. The current paradigm is that sub-Neptunes on close-in orbits evolve into super-Earths via atmospheric escape driven by high-energy stellar irradiation. We used an integrated hydrodynamic-radiation-chemical network model of the outflow to demonstrate that this escape is modulated by the abundance of H<sub>2<sub/>O, which is an efficient infrared coolant. Increasing the H<sub>2<sub/>O/H<sub>2<sub/> at the base of the flow induces a 1 dex decline in the escape rate, with definitive consequences for the retention of envelopes over Gyr. We show that saturation limits on H<sub>2<sub/>O in the upper atmospheres of temperate sub-Neptunes could explain the paradoxical observation that these objects disappear more rapidly than their counterparts closer to their host stars. We also propose that the scarcity of sub-Neptunes around very low-mass stars could be related to the water-poor chemistry of their antecedent protoplanetary disks. Observations of atmospheric H<sub>2<sub/>O by <i>JWST<i/> as well as searches for atmospheric escape from younger planets using H and He lines could test these predictions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202453619
E. Lellouch, I. Wong, P. Lavvas, T. Bertrand, G. Villanueva, J. Stansberry, B. Holler, N. Pinilla-Alonso, F. Merlin, A. C. Souza-Feliciano, K. Murray
<i>Context.<i/> Pluto possesses a tenuous, time-variable, N<sub>2<sub/>-dominated atmosphere, with extensive haze. Previous spectroscopic observations from the ground at near-infrared (NIR) and submillimeter (submm) wavelengths and New Horizons in the ultraviolet (UV) have revealed a Titan-like atmosphere with rich N<sub>2<sub/>-CH<sub>4<sub/> photochemistry. The mid-infrared (MIR) range of Pluto’s spectrum, however, has remained out of reach thus far.<i>Aims.<i/> Taking advantage of JWST sensitivity, our goal is to obtain new insights into Pluto’s atmospheric gas and haze composition using mid-IR spectroscopy.<i>Methods.<i/> In May 2023, we used JWST/MIRI MRS to acquire a high signal-to-noise (S/N) spectrum of Pluto over 4.9–27 μm, finally opening up the MIR spectral range for Pluto. The data were analyzed with a standard radiative transfer code, including the solar and thermal components, and the gas and haze emission, using gas vertical distributions from photochemical models as templates.<i>Results.<i/> The Pluto spectrum consists of the superposition of solar light reflected off Pluto’s surface, surface thermal emission, gas thermal and non-thermal emission, and haze emission. The solar reflected component shows absorption by CH<sub>4<sub/>, CH<sub>3<sub/>D, and C<sub>2<sub/>H<sub>4<sub/> surface ices. Spectral signatures of C<sub>2<sub/>H<sub>6<sub/>, C<sub>2<sub/>H<sub>2<sub/>, CH<sub>3<sub/>C<sub>2<sub/>H, and C<sub>4<sub/>H<sub>2<sub/> gases are strongly detected over 12–16 μm, broadly probing the stratopause region (altogether spanning 15–100 km). Unexpectedly, we also detect fluorescence (non-LTE) emission from gas CH<sub>4<sub/> (<i>ν<i/><sub>4<sub/> and hot bands) and CH<sub>3<sub/>D (<i>ν<i/><sub>6<sub/> band) in the 7–9 μm range, indicating excitation temperatures that are much higher than Pluto’s atmosphere kinetic temperature. The C<sub>2<sub/>H<sub>6<sub/> abundance agrees very well with photochemical models, but those of CH<sub>3<sub/>C<sub>2<sub/>H, and C<sub>4<sub/>H<sub>2<sub/> are about five and ten times lower than model predictions, respectively. The C<sub>2<sub/>H<sub>2<sub/> 12.9–14.7 μm emission (<i>ν<i/><sub>5<sub/>) is imperfectly fit and may point to a less steep C<sub>2<sub/>H<sub>2<sub/> profile than in model predictions or (perhaps more likely) to non-LTE effects on this band. Remarkably, C<sub>2<sub/>HD is detected at 14.75 μm, yielding a (D/H)<sub>C<sub>2<sub/>H<sub>2<sub/><sub/> ratio equal to (3±1) terrestrial. Also, HCN has been tentatively observed and upper limits on several other gases (C<sub>2<sub/>H<sub>4<sub/>, C<sub>3<sub/>H<sub>8<sub/>, C<sub>6<sub/>H<sub>6<sub/>, HC<sub>3<sub/>N, and CO<sub>2<sub/>) are obtained. The haze emission is clearly present over 13–20 μm and characterized by emission peaks at 15.45 μm, 14.58 μm, and maybe 13.60 μm. The haze spectrum is very different from Titan’s and points to the presence of pure or mixed ices (e.g., C<sub>4<sub/>H<sub>2<sub/>, C<sub>6<sub/>H<sub>6<sub/>),
{"title":"Pluto’s atmosphere gas and haze composition from JWST/MIRI spectroscopy","authors":"E. Lellouch, I. Wong, P. Lavvas, T. Bertrand, G. Villanueva, J. Stansberry, B. Holler, N. Pinilla-Alonso, F. Merlin, A. C. Souza-Feliciano, K. Murray","doi":"10.1051/0004-6361/202453619","DOIUrl":"https://doi.org/10.1051/0004-6361/202453619","url":null,"abstract":"<i>Context.<i/> Pluto possesses a tenuous, time-variable, N<sub>2<sub/>-dominated atmosphere, with extensive haze. Previous spectroscopic observations from the ground at near-infrared (NIR) and submillimeter (submm) wavelengths and New Horizons in the ultraviolet (UV) have revealed a Titan-like atmosphere with rich N<sub>2<sub/>-CH<sub>4<sub/> photochemistry. The mid-infrared (MIR) range of Pluto’s spectrum, however, has remained out of reach thus far.<i>Aims.<i/> Taking advantage of JWST sensitivity, our goal is to obtain new insights into Pluto’s atmospheric gas and haze composition using mid-IR spectroscopy.<i>Methods.<i/> In May 2023, we used JWST/MIRI MRS to acquire a high signal-to-noise (S/N) spectrum of Pluto over 4.9–27 μm, finally opening up the MIR spectral range for Pluto. The data were analyzed with a standard radiative transfer code, including the solar and thermal components, and the gas and haze emission, using gas vertical distributions from photochemical models as templates.<i>Results.<i/> The Pluto spectrum consists of the superposition of solar light reflected off Pluto’s surface, surface thermal emission, gas thermal and non-thermal emission, and haze emission. The solar reflected component shows absorption by CH<sub>4<sub/>, CH<sub>3<sub/>D, and C<sub>2<sub/>H<sub>4<sub/> surface ices. Spectral signatures of C<sub>2<sub/>H<sub>6<sub/>, C<sub>2<sub/>H<sub>2<sub/>, CH<sub>3<sub/>C<sub>2<sub/>H, and C<sub>4<sub/>H<sub>2<sub/> gases are strongly detected over 12–16 μm, broadly probing the stratopause region (altogether spanning 15–100 km). Unexpectedly, we also detect fluorescence (non-LTE) emission from gas CH<sub>4<sub/> (<i>ν<i/><sub>4<sub/> and hot bands) and CH<sub>3<sub/>D (<i>ν<i/><sub>6<sub/> band) in the 7–9 μm range, indicating excitation temperatures that are much higher than Pluto’s atmosphere kinetic temperature. The C<sub>2<sub/>H<sub>6<sub/> abundance agrees very well with photochemical models, but those of CH<sub>3<sub/>C<sub>2<sub/>H, and C<sub>4<sub/>H<sub>2<sub/> are about five and ten times lower than model predictions, respectively. The C<sub>2<sub/>H<sub>2<sub/> 12.9–14.7 μm emission (<i>ν<i/><sub>5<sub/>) is imperfectly fit and may point to a less steep C<sub>2<sub/>H<sub>2<sub/> profile than in model predictions or (perhaps more likely) to non-LTE effects on this band. Remarkably, C<sub>2<sub/>HD is detected at 14.75 μm, yielding a (D/H)<sub>C<sub>2<sub/>H<sub>2<sub/><sub/> ratio equal to (3±1) terrestrial. Also, HCN has been tentatively observed and upper limits on several other gases (C<sub>2<sub/>H<sub>4<sub/>, C<sub>3<sub/>H<sub>8<sub/>, C<sub>6<sub/>H<sub>6<sub/>, HC<sub>3<sub/>N, and CO<sub>2<sub/>) are obtained. The haze emission is clearly present over 13–20 μm and characterized by emission peaks at 15.45 μm, 14.58 μm, and maybe 13.60 μm. The haze spectrum is very different from Titan’s and points to the presence of pure or mixed ices (e.g., C<sub>4<sub/>H<sub>2<sub/>, C<sub>6<sub/>H<sub>6<sub/>),","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202452519
R. C. Arango-Toro, O. Ilbert, L. Ciesla, M. Shuntov, G. Aufort, W. Mercier, C. Laigle, M. Franco, M. Bethermin, D. Le Borgne, Y. Dubois, H. J. McCracken, L. Paquereau, M. Huertas-Company, J. Kartaltepe, C. M. Casey, H. Akins, N. Allen, I. Andika, M. Brinch, N. E. Drakos, A. Faisst, G. Gozaliasl, S. Harish, A. Kaminsky, A. Koekemoer, V. Kokorev, D. Liu, G. Magdis, C. L. Martin, T. Moutard, J. Rhodes, R. M. Rich, B. Robertson, D. B. Sanders, K. Sheth, M. Talia, S. Toft, L. Tresse, F. Valentino, A. Vijayan, J. Weaver
Context. The stellar mass-star formation rate (M⋆ − SFR) plane is an essential diagnostic to separate galaxy populations. However, we still lack a clear picture of how galaxies move within this plane along cosmic time.Aims. This study aims to provide an observational description of galaxy migrations in the M⋆ − SFR plane based on the reconstructed star formation histories (SFH) of a sample of galaxies at redshift z < 4. Ultimately, this study seeks to provide insight into physical processes driving star formation.Methods. We used data from the COSMOS field, which provides extensive multi-wavelength coverage. We selected a sample of 299131 galaxies at z < 4 with the COSMOS-Web NIRCam data at a magnitude of mF444W < 27 over a large area of 0.54 deg2. We utilized the SED modeling code CIGALE, which incorporates non-parametric SFHs, to derive the physical properties and reconstruct the SFHs of this galaxy sample. To characterize the SFHs and interpret the galaxies’ movements on the M⋆ − SFR plane, for each galaxy we also defined a migration vector in order to track the direction (ΦΔt[deg]) and velocity norm (rΔt[dex/Gyr]) of the evolutionary path over the M⋆ − SFR plane. We quantified the quality at which these migration vectors can be reconstructed using the HORIZON-AGN cosmological hydrodynamical simulation.Results. We find that galaxies within the main sequence exhibit the lowest amplitude in their migration and a large dispersion in the direction of their movements. We interpret this result as galaxies oscillating within the galaxy main sequence. By using their migration vectors to find the position of main-sequence progenitors, we obtained that most of the progenitors were already on the main sequence as defined one billion years earlier. We find that galaxies within the starburst or passive region of the M⋆ − SFR plane have very homogeneous properties in terms of recent SFH (< 1 Gyr). Starburst galaxies assembled half of their stellar mass within the last 350 Myr, and this population originates from the main sequence. Galaxies in the passive region of the plane show a homogeneous declining SFH over the full considered redshift range. We identified massive galaxies already in the passive region at 3.5 < z < 4, and their number density increases continuously with cosmic time. The progenitors of passive galaxies are distributed over a large range of SFRs, with less than 20% of passive galaxies being starburst 1 Gyr earlier, thus shedding light on rapid quenching channels.Conclusions. Using reconstructed SFHs up to z < 4, we propose a coherent picture of how galaxies migrate over cosmic time in the M⋆ − SFR plane, highlighting the connection between major phases in the SFH.
{"title":"COSMOS-Web: A history of galaxy migrations over the stellar mass–star formation rate plane","authors":"R. C. Arango-Toro, O. Ilbert, L. Ciesla, M. Shuntov, G. Aufort, W. Mercier, C. Laigle, M. Franco, M. Bethermin, D. Le Borgne, Y. Dubois, H. J. McCracken, L. Paquereau, M. Huertas-Company, J. Kartaltepe, C. M. Casey, H. Akins, N. Allen, I. Andika, M. Brinch, N. E. Drakos, A. Faisst, G. Gozaliasl, S. Harish, A. Kaminsky, A. Koekemoer, V. Kokorev, D. Liu, G. Magdis, C. L. Martin, T. Moutard, J. Rhodes, R. M. Rich, B. Robertson, D. B. Sanders, K. Sheth, M. Talia, S. Toft, L. Tresse, F. Valentino, A. Vijayan, J. Weaver","doi":"10.1051/0004-6361/202452519","DOIUrl":"https://doi.org/10.1051/0004-6361/202452519","url":null,"abstract":"<i>Context.<i/> The stellar mass-star formation rate (<i>M<i/><sub>⋆<sub/> − SFR) plane is an essential diagnostic to separate galaxy populations. However, we still lack a clear picture of how galaxies move within this plane along cosmic time.<i>Aims.<i/> This study aims to provide an observational description of galaxy migrations in the <i>M<i/><sub>⋆<sub/> − SFR plane based on the reconstructed star formation histories (SFH) of a sample of galaxies at redshift <i>z<i/> < 4. Ultimately, this study seeks to provide insight into physical processes driving star formation.<i>Methods.<i/> We used data from the COSMOS field, which provides extensive multi-wavelength coverage. We selected a sample of 299131 galaxies at <i>z<i/> < 4 with the COSMOS-Web NIRCam data at a magnitude of <i>m<i/><sub>F444W<sub/> < 27 over a large area of 0.54 deg<sup>2<sup/>. We utilized the SED modeling code CIGALE, which incorporates non-parametric SFHs, to derive the physical properties and reconstruct the SFHs of this galaxy sample. To characterize the SFHs and interpret the galaxies’ movements on the <i>M<i/><sub>⋆<sub/> − SFR plane, for each galaxy we also defined a migration vector in order to track the direction (Φ<sub>Δ<i>t<i/><sub/>[deg]) and velocity norm (<i>r<i/><sub>Δ<i>t<i/><sub/>[dex/Gyr]) of the evolutionary path over the <i>M<i/><sub>⋆<sub/> − SFR plane. We quantified the quality at which these migration vectors can be reconstructed using the HORIZON-AGN cosmological hydrodynamical simulation.<i>Results.<i/> We find that galaxies within the main sequence exhibit the lowest amplitude in their migration and a large dispersion in the direction of their movements. We interpret this result as galaxies oscillating within the galaxy main sequence. By using their migration vectors to find the position of main-sequence progenitors, we obtained that most of the progenitors were already on the main sequence as defined one billion years earlier. We find that galaxies within the starburst or passive region of the <i>M<i/><sub>⋆<sub/> − SFR plane have very homogeneous properties in terms of recent SFH (< 1 Gyr). Starburst galaxies assembled half of their stellar mass within the last 350 Myr, and this population originates from the main sequence. Galaxies in the passive region of the plane show a homogeneous declining SFH over the full considered redshift range. We identified massive galaxies already in the passive region at 3.5 < <i>z<i/> < 4, and their number density increases continuously with cosmic time. The progenitors of passive galaxies are distributed over a large range of SFRs, with less than 20% of passive galaxies being starburst 1 Gyr earlier, thus shedding light on rapid quenching channels.<i>Conclusions.<i/> Using reconstructed SFHs up to <i>z<i/> < 4, we propose a coherent picture of how galaxies migrate over cosmic time in the <i>M<i/><sub>⋆<sub/> − SFR plane, highlighting the connection between major phases in the SFH.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202453042
Haifeng Yang, Boyu Zhang, Jianghui Cai, Han Qu, Aiyu Zheng, Jing Hao, Xin Chen, Xujun Zhao, Yaling Xun
The missing satellite problem remains a central issue of the Lambda cold dark matter (ΛCDM) model. On a small scale, the number of observed dwarf galaxies is still fewer than the number predicted by existing theories. Therefore, finding fainter dwarf galaxies in deeper images is crucial for refining the existing theoretical framework. In this study, we propose an end-to-end automatic identification scheme for small size and faint dwarf galaxies based on the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys photometric images, and we provide a batch of dwarf galaxy candidates. We develop a dwarf galaxy automatic detection model, YOLO-DG, based on the YOLOv7 framework, and we achieve a precision of 88.2% and a recall of 89.1% on the test set. We identify 742 251 dwarf galaxy candidates across the entire DESI DR9 footprint using YOLO-DG, with their spectral redshifts concentrated in the range of 0–0.1. The faintest dwarf galaxy candidates detected by YOLO-DG have magnitudes of 31.61, 27.62, and 32.78 mag in the g, r, and z bands, respectively. We identify 95 230 local volume dwarf galaxy candidates, 33 of which are identified based on spectral redshift. The half-light radius of the smallest local volume dwarf galaxy candidate is 0.31 arcsec. Finally, we provide a complete catalogue of local volume dwarf galaxy candidates.
{"title":"An automatic detection method for small size dwarf galaxy candidates","authors":"Haifeng Yang, Boyu Zhang, Jianghui Cai, Han Qu, Aiyu Zheng, Jing Hao, Xin Chen, Xujun Zhao, Yaling Xun","doi":"10.1051/0004-6361/202453042","DOIUrl":"https://doi.org/10.1051/0004-6361/202453042","url":null,"abstract":"The missing satellite problem remains a central issue of the Lambda cold dark matter (ΛCDM) model. On a small scale, the number of observed dwarf galaxies is still fewer than the number predicted by existing theories. Therefore, finding fainter dwarf galaxies in deeper images is crucial for refining the existing theoretical framework. In this study, we propose an end-to-end automatic identification scheme for small size and faint dwarf galaxies based on the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys photometric images, and we provide a batch of dwarf galaxy candidates. We develop a dwarf galaxy automatic detection model, YOLO-DG, based on the YOLOv7 framework, and we achieve a precision of 88.2% and a recall of 89.1% on the test set. We identify 742 251 dwarf galaxy candidates across the entire DESI DR9 footprint using YOLO-DG, with their spectral redshifts concentrated in the range of 0–0.1. The faintest dwarf galaxy candidates detected by YOLO-DG have magnitudes of 31.61, 27.62, and 32.78 mag in the <i>g<i/>, <i>r<i/>, and <i>z<i/> bands, respectively. We identify 95 230 local volume dwarf galaxy candidates, 33 of which are identified based on spectral redshift. The half-light radius of the smallest local volume dwarf galaxy candidate is 0.31 arcsec. Finally, we provide a complete catalogue of local volume dwarf galaxy candidates.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"115 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202453479
A. A. Chrimes, A. J. Levan, J. D. Lyman, A. Borghese, V. S. Dhillon, P. Esposito, M. Fraser, A. S. Fruchter, D. Götz, R. A. Hounsell, G. L. Israel, C. Kouveliotou, S. Mereghetti, R. P. Mignani, R. Perna, N. Rea, I. Skillen, D. Steeghs, N. R. Tanvir, K. Wiersema, N. J. Wright, S. Zane
Aims. Soft gamma repeaters (SGRs) are highly magnetised neutron stars (magnetars) notable for their gamma-ray and X-ray outbursts. We used near-infrared (NIR) imaging of SGR 0501+4516 in the days, weeks, and years after its 2008 outburst to characterise the multi-wavelength emission, and to obtain a proper motion from our long temporal baseline observations.Methods. We present short- and long-term monitoring of the IR counterpart of SGR 0501+4516 and a measurement of its proper motion. Unlike most magnetars, the source has only moderate foreground extinction with minimal crowding. Our observations began only ∼2 hours after the first activation of SGR 0501+4516 in August 2008 and continued for ∼4 years, including two epochs of Hubble Space Telescope (HST) imaging. The proper motion constraint was improved using a third HST epoch from 10 years later.Results. The NIR and X-rays faded slowly during the first week, which was followed by a steeper power-law decay. The behaviour is satisfactorily fit by a broken power law. Three epochs of HST imaging with a 10-year baseline allowed us to determine the quiescent level and to measure a proper motion of μ = 5.4 ± 0.6 mas yr−1. This corresponds to a low transverse peculiar velocity of v ≃ 51 ± 14 km s−1 (at 2 kpc). The magnitude and direction of the proper motion rules out supernova remnant HB9 as the birth site. We can find no other supernova remnants or groups of massive stars within the region traversed by SGR 0501+4516 during its characteristic lifetime (∼20 kyr).Conclusions. Our observations of SGR 0501+4516 suggest three possibilities: that some magnetars are significantly older than expected, that their progenitors produce low supernova ejecta masses, or that they can be formed through accretion-induced collapse or low-mass neutron star mergers. Although the progenitor of SGR 0501+4516 remains unclear, we propose that SGR 0501+4516 is the best Galactic candidate for a magnetar formed through a mechanism other than massive star core-collapse.
{"title":"The infrared counterpart and proper motion of magnetar SGR 0501+4516","authors":"A. A. Chrimes, A. J. Levan, J. D. Lyman, A. Borghese, V. S. Dhillon, P. Esposito, M. Fraser, A. S. Fruchter, D. Götz, R. A. Hounsell, G. L. Israel, C. Kouveliotou, S. Mereghetti, R. P. Mignani, R. Perna, N. Rea, I. Skillen, D. Steeghs, N. R. Tanvir, K. Wiersema, N. J. Wright, S. Zane","doi":"10.1051/0004-6361/202453479","DOIUrl":"https://doi.org/10.1051/0004-6361/202453479","url":null,"abstract":"<i>Aims.<i/> Soft gamma repeaters (SGRs) are highly magnetised neutron stars (magnetars) notable for their gamma-ray and X-ray outbursts. We used near-infrared (NIR) imaging of SGR 0501+4516 in the days, weeks, and years after its 2008 outburst to characterise the multi-wavelength emission, and to obtain a proper motion from our long temporal baseline observations.<i>Methods.<i/> We present short- and long-term monitoring of the IR counterpart of SGR 0501+4516 and a measurement of its proper motion. Unlike most magnetars, the source has only moderate foreground extinction with minimal crowding. Our observations began only ∼2 hours after the first activation of SGR 0501+4516 in August 2008 and continued for ∼4 years, including two epochs of <i>Hubble<i/> Space Telescope (HST) imaging. The proper motion constraint was improved using a third HST epoch from 10 years later.<i>Results.<i/> The NIR and X-rays faded slowly during the first week, which was followed by a steeper power-law decay. The behaviour is satisfactorily fit by a broken power law. Three epochs of HST imaging with a 10-year baseline allowed us to determine the quiescent level and to measure a proper motion of <i>μ<i/> = 5.4 ± 0.6 mas yr<sup>−1<sup/>. This corresponds to a low transverse peculiar velocity of <i>v<i/> ≃ 51 ± 14 km s<sup>−1<sup/> (at 2 kpc). The magnitude and direction of the proper motion rules out supernova remnant HB9 as the birth site. We can find no other supernova remnants or groups of massive stars within the region traversed by SGR 0501+4516 during its characteristic lifetime (∼20 kyr).<i>Conclusions.<i/> Our observations of SGR 0501+4516 suggest three possibilities: that some magnetars are significantly older than expected, that their progenitors produce low supernova ejecta masses, or that they can be formed through accretion-induced collapse or low-mass neutron star mergers. Although the progenitor of SGR 0501+4516 remains unclear, we propose that SGR 0501+4516 is the best Galactic candidate for a magnetar formed through a mechanism other than massive star core-collapse.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"953 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15DOI: 10.1051/0004-6361/202554180
V. Ossenkopf-Okada, A. Karska, M. Benedettini, D. Colombo, R. Simon
Context. Models predict that atomic carbon occurs at the surface and in the process of the formation of molecular clouds. This makes its fine-structure transitions a diagnostic of cloud formation.Aims. We study the distribution of atomic carbon in a small inconspicuous region toward the outer Galaxy that might be representative for a large fraction of the molecular gas of the Milky Way that is not directly affected by star formation.Methods. We observed a small strip of 5 arcminutes in the so-called Forgotten Quadrant, the third quadrant of the Milky Way, with the APEX telescope in the 3P1−3P0 [C I] transition of atomic carbon and the J = 2−1 transition of the three most abundant CO isotopologs. We compared their distribution with existing measurements of the gas column density and of ionized carbon.Results. The atomic carbon shows a very smooth distribution with the smallest gradient along the strip compared to the other lines. It is always brighter than 13CO, and in one velocity component, it is even brighter than CO. In contrast to observations of many star-forming regions, the [C I] emission seems to extend beyond the molecular gas. This is in line with models of photon-dominated regions (PDRs). However, a standard PDR model fit to the observations fails because the models either predict more molecular gas than observed, traced through C18O, or more diffuse gas than observed, traced through [C II]. The carbon budget in the gas phase does not add up to the same column seen through dust emission.Conclusions. To understand the [C I] emission from galaxies, it is necessary to obtain the full statistics for the quiescent gas outside of the star-forming regions that behaves significantly different from dense gas that is exposed to high-ultraviolet fields.
{"title":"Extended atomic carbon around molecular clouds","authors":"V. Ossenkopf-Okada, A. Karska, M. Benedettini, D. Colombo, R. Simon","doi":"10.1051/0004-6361/202554180","DOIUrl":"https://doi.org/10.1051/0004-6361/202554180","url":null,"abstract":"<i>Context.<i/> Models predict that atomic carbon occurs at the surface and in the process of the formation of molecular clouds. This makes its fine-structure transitions a diagnostic of cloud formation.<i>Aims.<i/> We study the distribution of atomic carbon in a small inconspicuous region toward the outer Galaxy that might be representative for a large fraction of the molecular gas of the Milky Way that is not directly affected by star formation.<i>Methods.<i/> We observed a small strip of 5 arcminutes in the so-called Forgotten Quadrant, the third quadrant of the Milky Way, with the APEX telescope in the <sup>3<sup/>P<sub>1<sub/>−<sup>3<sup/>P<sub>0<sub/> [C I] transition of atomic carbon and the <i>J<i/> = 2−1 transition of the three most abundant CO isotopologs. We compared their distribution with existing measurements of the gas column density and of ionized carbon.<i>Results.<i/> The atomic carbon shows a very smooth distribution with the smallest gradient along the strip compared to the other lines. It is always brighter than <sup>13<sup/>CO, and in one velocity component, it is even brighter than CO. In contrast to observations of many star-forming regions, the [C I] emission seems to extend beyond the molecular gas. This is in line with models of photon-dominated regions (PDRs). However, a standard PDR model fit to the observations fails because the models either predict more molecular gas than observed, traced through C<sup>18<sup/>O, or more diffuse gas than observed, traced through [C II]. The carbon budget in the gas phase does not add up to the same column seen through dust emission.<i>Conclusions.<i/> To understand the [C I] emission from galaxies, it is necessary to obtain the full statistics for the quiescent gas outside of the star-forming regions that behaves significantly different from dense gas that is exposed to high-ultraviolet fields.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143836760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-14DOI: 10.1051/0004-6361/202453295
A. R. da Silva, R. Smiljanic
Context. R-process enhanced metal-poor stars ([Eu/Fe] ≥ +0.3 and [Fe/H] ≤ −1.0) are rare objects, the study of which can provide clues as to the astrophysical sites of the rapid neutron capture process.Aims. In this study, we investigate the detailed chemical abundance patterns of two of these anomalous stars, originally identified among stars observed by the GALAH survey. Our aim is to obtain the detailed chemical abundance pattern of these stars with spectroscopy at a higher resolution and signal-to-noise ratio.Methods. We used a calibration of the infrared flux method to determine accurate effective temperatures, and Gaia parallaxes together with broadband photometry and theoretical bolometric corrections to determine surface gravity. Metallicities and chemical abundances were determined with model atmospheres and spectrum synthesis. We also integrated stellar orbits for a complete chemodynamic analysis.Results. We determined abundances for up to 47 chemical species (44 elements), of which 27 are neutron-capture elements. Corrections because of deviations from the local thermodynamical equilibrium were applied to the metallicities and 12 elements. We find that one of the stars, BPS CS 29529-0089, is a proto-disk star of the Milky Way of r-II type, with [Eu/Fe] = +1.79 dex. The second star, TYC 9219-2422-1, is part of the halo and associated with the Gaia-Sausage-Enceladus merger event. It is of r-I type with [Eu/Fe] = +0.54. Abundances of Th are also provided for both stars.Conclusions. BPS CS 29529-0089 is the most extreme example of an r-process enhanced star known with disk-like kinematics and not carbon enhanced. TYC 9219-2422-1 is found to be an archetypal Gaia-Sausage-Enceladus star. Their abundances of C, Mg, Ni, Sc, Mn, and Al seem consistent with expectations for stars enriched by a single population III core collapse supernova, despite their relatively high metallicities ([Fe/H] ∼ −2.4).
{"title":"Discovery of a pair of very metal-poor stars enriched in neutron-capture elements","authors":"A. R. da Silva, R. Smiljanic","doi":"10.1051/0004-6361/202453295","DOIUrl":"https://doi.org/10.1051/0004-6361/202453295","url":null,"abstract":"<i>Context.<i/> R-process enhanced metal-poor stars ([Eu/Fe] ≥ +0.3 and [Fe/H] ≤ −1.0) are rare objects, the study of which can provide clues as to the astrophysical sites of the rapid neutron capture process.<i>Aims.<i/> In this study, we investigate the detailed chemical abundance patterns of two of these anomalous stars, originally identified among stars observed by the GALAH survey. Our aim is to obtain the detailed chemical abundance pattern of these stars with spectroscopy at a higher resolution and signal-to-noise ratio.<i>Methods.<i/> We used a calibration of the infrared flux method to determine accurate effective temperatures, and <i>Gaia<i/> parallaxes together with broadband photometry and theoretical bolometric corrections to determine surface gravity. Metallicities and chemical abundances were determined with model atmospheres and spectrum synthesis. We also integrated stellar orbits for a complete chemodynamic analysis.<i>Results.<i/> We determined abundances for up to 47 chemical species (44 elements), of which 27 are neutron-capture elements. Corrections because of deviations from the local thermodynamical equilibrium were applied to the metallicities and 12 elements. We find that one of the stars, BPS CS 29529-0089, is a proto-disk star of the Milky Way of r-II type, with [Eu/Fe] = +1.79 dex. The second star, TYC 9219-2422-1, is part of the halo and associated with the Gaia-Sausage-Enceladus merger event. It is of r-I type with [Eu/Fe] = +0.54. Abundances of Th are also provided for both stars.<i>Conclusions.<i/> BPS CS 29529-0089 is the most extreme example of an r-process enhanced star known with disk-like kinematics and not carbon enhanced. TYC 9219-2422-1 is found to be an archetypal Gaia-Sausage-Enceladus star. Their abundances of C, Mg, Ni, Sc, Mn, and Al seem consistent with expectations for stars enriched by a single population III core collapse supernova, despite their relatively high metallicities ([Fe/H] ∼ −2.4).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"136 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-14DOI: 10.1051/0004-6361/202553811
Cheongho Han, Weicheng Zang, Andrzej Udalski, Chung-Uk Lee, Ian A. Bond, Yongxin Wen, Bo Ma, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Hongjing Yang, Jennifer C. Yee, Doeon Kim, Dong-Jin Kim, Sang-Mok Cha, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Fumio Abe, Ken Bando, David P. Bennett, Aparna Bhattacharya, Akihiko Fukui, Ryusei Hamada, Shunya Hamada, Naoto Hamasaki, Yuki Hirao, Stela Ishitani Silva, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Tutumi Nagai, Kansuke Nunota, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Takahiro Sumi, Daisuke Suzuki, Sean K. Terry, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama
Aims. The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies.Methods. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis.Results. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be M1 = (1.05 ± 0.20) M⊙, M2 = (0.36 ± 0.07) M⊙, and the distance to the lens was found to be DL = (3.11 ± 0.40) kpc.
{"title":"Analyses of anomalous lensing events detected from the UKIRT microlensing survey","authors":"Cheongho Han, Weicheng Zang, Andrzej Udalski, Chung-Uk Lee, Ian A. Bond, Yongxin Wen, Bo Ma, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Hongjing Yang, Jennifer C. Yee, Doeon Kim, Dong-Jin Kim, Sang-Mok Cha, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Fumio Abe, Ken Bando, David P. Bennett, Aparna Bhattacharya, Akihiko Fukui, Ryusei Hamada, Shunya Hamada, Naoto Hamasaki, Yuki Hirao, Stela Ishitani Silva, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Tutumi Nagai, Kansuke Nunota, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Takahiro Sumi, Daisuke Suzuki, Sean K. Terry, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama","doi":"10.1051/0004-6361/202553811","DOIUrl":"https://doi.org/10.1051/0004-6361/202553811","url":null,"abstract":"<i>Aims.<i/> The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies.<i>Methods.<i/> The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis.<i>Results.<i/> Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be <i>M<i/><sub>1<sub/> = (1.05 ± 0.20) <i>M<i/><sub>⊙<sub/>, <i>M<i/><sub>2<sub/> = (0.36 ± 0.07) <i>M<i/><sub>⊙<sub/>, and the distance to the lens was found to be <i>D<i/><sub>L<sub/> = (3.11 ± 0.40) kpc.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-14DOI: 10.1051/0004-6361/202453409
Mika Juvela
Context. Radiative transfer (RT) effects need to be taken into account when analysing spectral line observations. When the data are not sufficient for detailed modelling, simpler methods are needed. The escape probability formalism (EPF) is one such tool.Aims. We wish to quantify the model errors in the EPF analysis of interstellar clouds and cores.Methods. We introduce PEP, a parallel programme for calculating fast EPF parameters quickly. We modelled a full RT to generate synthetic observations for various cloud models. We examined these with the PEP programme, comparing these results to the actual beam-averaged kinetic temperatures, column densities, and volume densities.Results. PEP enables the calculation of even millions of parameter combinations in a matter of seconds. However, the simple assumptions of EPF can lead to significant errors. In these tests, the errors were typically within a factor of 2, but could (in some cases) rise to one full order of magnitude. The model errors are thus similar or even larger than the statistical errors caused by the typical observational noise. Due to degeneracies, the parameter combinations were shown to be better constrained than the individual parameters. The model errors could be reduced by using full radiative transfer modelling. However, in the absence of full knowledge of the source structure, the errors are difficult to quantify. We also present a method for approximate handling of hyperfine structure lines in EPF calculations.Conclusions. Both the observational statistical errors and the model errors need to be considered when estimating the reliability of EPF results. Full RT modelling is needed to better understand the true uncertainties.
{"title":"Fast spectral line calculations with the escape probability method and tests using synthetic observations of interstellar clouds","authors":"Mika Juvela","doi":"10.1051/0004-6361/202453409","DOIUrl":"https://doi.org/10.1051/0004-6361/202453409","url":null,"abstract":"<i>Context.<i/> Radiative transfer (RT) effects need to be taken into account when analysing spectral line observations. When the data are not sufficient for detailed modelling, simpler methods are needed. The escape probability formalism (EPF) is one such tool.<i>Aims.<i/> We wish to quantify the model errors in the EPF analysis of interstellar clouds and cores.<i>Methods.<i/> We introduce PEP, a parallel programme for calculating fast EPF parameters quickly. We modelled a full RT to generate synthetic observations for various cloud models. We examined these with the PEP programme, comparing these results to the actual beam-averaged kinetic temperatures, column densities, and volume densities.<i>Results.<i/> PEP enables the calculation of even millions of parameter combinations in a matter of seconds. However, the simple assumptions of EPF can lead to significant errors. In these tests, the errors were typically within a factor of 2, but could (in some cases) rise to one full order of magnitude. The model errors are thus similar or even larger than the statistical errors caused by the typical observational noise. Due to degeneracies, the parameter combinations were shown to be better constrained than the individual parameters. The model errors could be reduced by using full radiative transfer modelling. However, in the absence of full knowledge of the source structure, the errors are difficult to quantify. We also present a method for approximate handling of hyperfine structure lines in EPF calculations.<i>Conclusions.<i/> Both the observational statistical errors and the model errors need to be considered when estimating the reliability of EPF results. Full RT modelling is needed to better understand the true uncertainties.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"183 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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