Pub Date : 2024-09-05DOI: 10.1051/0004-6361/202244087
René Heller
The ~23 Myr young star β Pictoris (β Pic) is a laboratory for planet formation studies because of its observed debris disk, its directly imaged super-Jovian planets β Pic b and c, and the evidence of extrasolar comets that regularly transit in front of the star. The most recent evidence of exocometary transits around β Pic came from stellar photometric time series obtained with the TESS space mission. Previous analyses of these transits constrained the orbital distribution of the underlying exocomet population to a range between about 0.03 and 1.3 AU assuming a fixed transit impact parameter. We examine the distribution of the observed transit durations (Δt) to infer the orbital surface density distribution (δ) of the underlying exocomet sample. The effect of the geometric transit probability for circular orbits was properly taken into account, but we assumed that the radius of the transiting comets and their possible clouds of evaporating material are much smaller than the stellar radius. We show that a narrow belt of exocomets around β Pic, in which the transit impact parameters are randomized but the orbital semimajor axes are equal, results in a pile-up of long transit durations. This is in contrast to observations, which reveal a pile-up of short transit durations (Δt ≈ 0.1 d) and a tail of only a few transits with Δt > 0.4 d. A flat density distribution of exocomets between about 0.03 and 2.5 AU results in a better match between the resulting Δt distribution and the observations, but the slope of the predicted Δt histogram is not sufficiently steep. An even better match to the observations can be produced with a δ ∝ aβ power law. Our modeling reveals a best fit between the observed and predicted Δt distribution for β = −0.15−0.10+0.05. A more reasonable scenario in which the exocometary trajectories are modeled as hyperbolic orbits can also reproduce the observed Δt distribution to some extent. Future studies might reproduce the observed Δt distribution with a full exploration of the four-dimensional parameter space of highly eccentric orbits, and they might need to relax our assumption that the transiting objects are smaller than the stellar disk. The number of observed exocometary transits around β Pic is currently too small to validate the previously reported distinction of two distinct exocomet families, but this might be possible with future TESS observations of this star. Our results nevertheless imply that cometary material exists on highly eccentric orbits with a more extended range of semimajor axes than suggested by previous spectroscopic observations.
{"title":"Exocomet orbital distribution around β Pictoris","authors":"René Heller","doi":"10.1051/0004-6361/202244087","DOIUrl":"https://doi.org/10.1051/0004-6361/202244087","url":null,"abstract":"The ~23 Myr young star <i>β<i/> Pictoris (<i>β<i/> Pic) is a laboratory for planet formation studies because of its observed debris disk, its directly imaged super-Jovian planets <i>β<i/> Pic b and c, and the evidence of extrasolar comets that regularly transit in front of the star. The most recent evidence of exocometary transits around <i>β<i/> Pic came from stellar photometric time series obtained with the TESS space mission. Previous analyses of these transits constrained the orbital distribution of the underlying exocomet population to a range between about 0.03 and 1.3 AU assuming a fixed transit impact parameter. We examine the distribution of the observed transit durations (Δ<i>t<i/>) to infer the orbital surface density distribution (<i>δ<i/>) of the underlying exocomet sample. The effect of the geometric transit probability for circular orbits was properly taken into account, but we assumed that the radius of the transiting comets and their possible clouds of evaporating material are much smaller than the stellar radius. We show that a narrow belt of exocomets around <i>β<i/> Pic, in which the transit impact parameters are randomized but the orbital semimajor axes are equal, results in a pile-up of long transit durations. This is in contrast to observations, which reveal a pile-up of short transit durations (Δ<i>t<i/> ≈ 0.1 d) and a tail of only a few transits with Δ<i>t<i/> > 0.4 d. A flat density distribution of exocomets between about 0.03 and 2.5 AU results in a better match between the resulting Δ<i>t<i/> distribution and the observations, but the slope of the predicted Δ<i>t<i/> histogram is not sufficiently steep. An even better match to the observations can be produced with a <i>δ ∝ a<sup>β<sup/><i/> power law. Our modeling reveals a best fit between the observed and predicted Δ<i>t<i/> distribution for <i>β<i/> = −0.15<sub>−0.10<sub/><sup>+0.05<sup/>. A more reasonable scenario in which the exocometary trajectories are modeled as hyperbolic orbits can also reproduce the observed Δ<i>t<i/> distribution to some extent. Future studies might reproduce the observed Δ<i>t<i/> distribution with a full exploration of the four-dimensional parameter space of highly eccentric orbits, and they might need to relax our assumption that the transiting objects are smaller than the stellar disk. The number of observed exocometary transits around <i>β<i/> Pic is currently too small to validate the previously reported distinction of two distinct exocomet families, but this might be possible with future TESS observations of this star. Our results nevertheless imply that cometary material exists on highly eccentric orbits with a more extended range of semimajor axes than suggested by previous spectroscopic observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142142408","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 : 2024-09-03DOI: 10.1051/0004-6361/202450595
J. M. G. H. J. de Jong, R. J. van Weeren, F. Sweijen, J. B. R. Oonk, T. W. Shimwell, A. R. Offringa, L. K. Morabito, H. J. A. Röttgering, R. Kondapally, E. L. Escott, P. N. Best, M. Bondi, H. Ye, J. W. Petley
We present the deepest wide-field 115–166 MHz image at sub-arcsecond resolution spanning an area of 2.5° × 2.5° centred at the ELAIS-N1 deep field. To achieve this, we improved the direction-independent (DI) and direction-dependent (DD) calibrations for the International LOw Frequency ARray (LOFAR) Telescope. This enhancement enabled us to efficiently process 32 h of data from four different 8-h observations using the high-band antennas (HBAs) of all 52 stations, covering baselines up to approximately 2000 km across Europe. The DI calibration was improved by using an accurate sky model and refining the series of calibration steps on the in-field calibrator, while the DD calibration was improved by adopting a more automated approach for selecting the DD calibrators and inspecting the self-calibration on these sources. For our brightest calibrators, we also added an additional round of self-calibration for the Dutch core and remote stations in order to refine the solutions for shorter baselines. To complement our highest resolution at 0.3″, we also made intermediate resolution wide-field images at 0.6″ and 1.2″. Our resulting wide-field images achieve a central noise level of 14 μJy beam−1 at 0.3″, doubling the depth and uncovering four times more objects than the Lockman Hole deep field image at comparable resolution but with only 8 h of data. Compared to LOFAR imaging without the international stations, we note that due to the increased collecting area and the absence of confusion noise, we reached a point-source sensitivity comparable to a 500-h ELAIS-N1 6″ image with 16 times less observing time. Importantly, we have found that the computing costs for the same amount of data are almost halved (to about 139 000 CPU h per 8 h of data) compared to previous efforts, though they remain high. Our work underscores the value and feasibility of exploiting all Dutch and international LOFAR stations to make deep wide-field images at sub-arcsecond resolution.
{"title":"Into the depths: Unveiling ELAIS-N1 with LOFAR’s deepest sub-arcsecond wide-field images","authors":"J. M. G. H. J. de Jong, R. J. van Weeren, F. Sweijen, J. B. R. Oonk, T. W. Shimwell, A. R. Offringa, L. K. Morabito, H. J. A. Röttgering, R. Kondapally, E. L. Escott, P. N. Best, M. Bondi, H. Ye, J. W. Petley","doi":"10.1051/0004-6361/202450595","DOIUrl":"https://doi.org/10.1051/0004-6361/202450595","url":null,"abstract":"We present the deepest wide-field 115–166 MHz image at sub-arcsecond resolution spanning an area of 2.5° × 2.5° centred at the ELAIS-N1 deep field. To achieve this, we improved the direction-independent (DI) and direction-dependent (DD) calibrations for the International LOw Frequency ARray (LOFAR) Telescope. This enhancement enabled us to efficiently process 32 h of data from four different 8-h observations using the high-band antennas (HBAs) of all 52 stations, covering baselines up to approximately 2000 km across Europe. The DI calibration was improved by using an accurate sky model and refining the series of calibration steps on the in-field calibrator, while the DD calibration was improved by adopting a more automated approach for selecting the DD calibrators and inspecting the self-calibration on these sources. For our brightest calibrators, we also added an additional round of self-calibration for the Dutch core and remote stations in order to refine the solutions for shorter baselines. To complement our highest resolution at 0.3″, we also made intermediate resolution wide-field images at 0.6″ and 1.2″. Our resulting wide-field images achieve a central noise level of 14 μJy beam<sup>−1<sup/> at 0.3″, doubling the depth and uncovering four times more objects than the Lockman Hole deep field image at comparable resolution but with only 8 h of data. Compared to LOFAR imaging without the international stations, we note that due to the increased collecting area and the absence of confusion noise, we reached a point-source sensitivity comparable to a 500-h ELAIS-N1 6″ image with 16 times less observing time. Importantly, we have found that the computing costs for the same amount of data are almost halved (to about 139 000 CPU h per 8 h of data) compared to previous efforts, though they remain high. Our work underscores the value and feasibility of exploiting all Dutch and international LOFAR stations to make deep wide-field images at sub-arcsecond resolution.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131017","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 : 2024-09-03DOI: 10.1051/0004-6361/202449913
I. J. Lima, G. J. M. Luna, K. Mukai, A. S. Oliveira, J. L. Sokoloski, F. M. Walter, N. Palivanas, N. E. Nuñez, R. R. Souza, R. A. N. Araujo
White dwarf symbiotic binaries are detected in X-rays with luminosities in the range of 1030–1034 ergs s−1. Their X-ray emission arises either from the accretion disk boundary layer, from a region where the winds from both components collide, or from nuclear burning on the surface of the white dwarf (WD). In our continuous effort to identify X-ray-emitting symbiotic stars, we studied four systems using observations from the Neil Gehrels Swift Observatory and XMM-Newton satellites in X-rays and from Transiting Exoplanet Survey Satellite (TESS) in the optical. The X-ray spectra were fit with absorbed optically thin thermal plasma models that are either single- or multitemperature with kT < 8 keV for all targets. Based on the characteristics of their X-ray spectra, we classified BD Cam as possible β-type, V1261 Ori and CD −27 8661 as δ-type, and confirmed NQ Gem as β/δ-type. The δ-type X-ray emission most likely arises from the boundary layer of the accretion disk, while in the case of BD Cam, its mostly soft emission originates from shocks, possibly between the red giant and WD and disk winds. In general, we find that the observed X-ray emission is powered by accretion at a low accretion rate of about 10−11 M⊙ yr−1. The low ratio of X-ray to optical luminosities, however indicates that the accretion-disk boundary layer is mostly optically thick and tends to emit in the far or extreme UV. The detection of flickering in optical data provides evidence of the existence of an accretion disk.
白矮星共生双星在 X 射线中被探测到的光度范围为 1030-1034 尔格 s-1。它们的X射线发射要么来自吸积盘边界层，要么来自两个成分的风相撞的区域，要么来自白矮星（WD）表面的核燃烧。我们一直在努力寻找发射X射线的共生恒星，我们利用尼尔-盖尔斯-斯威夫特天文台（Neil Gehrels Swift Observatory）和XMM-牛顿（XMM-Newton）卫星的X射线观测数据，以及越轨系外行星巡天卫星（TESS）的光学观测数据，对四个系统进行了研究。对所有目标的 X 射线光谱都用吸收型光学薄热等离子体模型进行了拟合，这些模型要么是单温的，要么是多温的，kT < 8 keV。根据它们的 X 射线光谱特征，我们将 BD Cam 可能归为 β 型，V1261 Ori 和 CD -27 8661 归为 δ 型，并确认 NQ Gem 为 β/δ 型。δ型X射线辐射很可能来自于吸积盘的边界层，而BD Cam的大部分软辐射则来自于冲击，可能在红巨星和WD以及盘风之间。总的来说，我们发现观测到的 X 射线辐射是由低吸积率（约 10-11 M⊙ yr-1）的吸积所驱动的。然而，X射线光度与光学光度的低比值表明，吸积盘边界层大部分是光学厚层，倾向于在远紫外或极紫外辐射。在光学数据中探测到的闪烁现象为吸积盘的存在提供了证据。
{"title":"Symbiotic stars in X-rays","authors":"I. J. Lima, G. J. M. Luna, K. Mukai, A. S. Oliveira, J. L. Sokoloski, F. M. Walter, N. Palivanas, N. E. Nuñez, R. R. Souza, R. A. N. Araujo","doi":"10.1051/0004-6361/202449913","DOIUrl":"https://doi.org/10.1051/0004-6361/202449913","url":null,"abstract":"White dwarf symbiotic binaries are detected in X-rays with luminosities in the range of 10<sup>30<sup/>–10<sup>34<sup/> ergs s<sup>−1<sup/>. Their X-ray emission arises either from the accretion disk boundary layer, from a region where the winds from both components collide, or from nuclear burning on the surface of the white dwarf (WD). In our continuous effort to identify X-ray-emitting symbiotic stars, we studied four systems using observations from the <i>Neil Gehrels Swift<i/> Observatory and <i>XMM-Newton<i/> satellites in X-rays and from Transiting Exoplanet Survey Satellite (TESS) in the optical. The X-ray spectra were fit with absorbed optically thin thermal plasma models that are either single- or multitemperature with <i>kT<i/> < 8 keV for all targets. Based on the characteristics of their X-ray spectra, we classified BD Cam as possible <i>β<i/>-type, V1261 Ori and CD −27 8661 as <i>δ<i/>-type, and confirmed NQ Gem as <i>β<i/>/<i>δ<i/>-type. The <i>δ<i/>-type X-ray emission most likely arises from the boundary layer of the accretion disk, while in the case of BD Cam, its mostly soft emission originates from shocks, possibly between the red giant and WD and disk winds. In general, we find that the observed X-ray emission is powered by accretion at a low accretion rate of about 10<sup>−11<sup/> M<sub>⊙<sub/> yr<sup>−1<sup/>. The low ratio of X-ray to optical luminosities, however indicates that the accretion-disk boundary layer is mostly optically thick and tends to emit in the far or extreme UV. The detection of flickering in optical data provides evidence of the existence of an accretion disk.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131071","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 : 2024-09-03DOI: 10.1051/0004-6361/202450717
O. Balsalobre-Ruza, J. Lillo-Box, D. Barrado, A. C. M. Correia, J. P. Faria, P. Figueira, A. Leleu, P. Robutel, N. Santos, E. Herrero-Cisneros
Context. Co-orbital objects, also known as trojans, are frequently found in simulations of planetary system formation. In these configurations, a planet shares its orbit with other massive bodies. It is still unclear why there have not been any co-orbitals discovered thus far in exoplanetary systems (exotrojans) or even pairs of planets found in such a 1:1 mean motion resonance. Reconciling observations and theory is an open subject in the field.Aims. The main objective of the 𝒯ℛ𝒪𝒴 project is to conduct an exhaustive search for exotrojans using diverse observational techniques. In this work, we analyze the radial velocity time series informed by transits, focusing the search around low-mass stars.Methods. We employed the α-test method on confirmed planets searching for shifts between spectral and photometric mid-transit times. This technique is sensitive to mass imbalances within the planetary orbit, allowing us to identify non-negligible co-orbital masses.Results. Among the 95 transiting planets examined, we find one robust exotrojan candidate with a significant 3-σ detection. Additionally, 25 exoplanets show compatibility with the presence of exotrojan companions at a 1-σ level, requiring further observations to better constrain their presence. For two of those weak candidates, we find dimmings in their light curves within the predicted Lagrangian region. We established upper limits on the co-orbital masses for either the candidates and null detections.Conclusions. Our analysis reveals that current high-resolution spectrographs effectively rule out co-orbitals more massive than Saturn around low-mass stars. This work points out to dozens of targets that have the potential to better constraint their exotrojan upper mass limit with dedicated radial velocity observations. We also explored the potential of observing the secondary eclipses of the confirmed exoplanets in our sample to enhance the exotrojan search, ultimately leading to a more accurate estimation of the occurrence rate of exotrojans.
{"title":"The 𝒯ℛ𝒪𝒴 project","authors":"O. Balsalobre-Ruza, J. Lillo-Box, D. Barrado, A. C. M. Correia, J. P. Faria, P. Figueira, A. Leleu, P. Robutel, N. Santos, E. Herrero-Cisneros","doi":"10.1051/0004-6361/202450717","DOIUrl":"https://doi.org/10.1051/0004-6361/202450717","url":null,"abstract":"<i>Context.<i/> Co-orbital objects, also known as trojans, are frequently found in simulations of planetary system formation. In these configurations, a planet shares its orbit with other massive bodies. It is still unclear why there have not been any co-orbitals discovered thus far in exoplanetary systems (exotrojans) or even pairs of planets found in such a 1:1 mean motion resonance. Reconciling observations and theory is an open subject in the field.<i>Aims.<i/> The main objective of the 𝒯ℛ𝒪𝒴 project is to conduct an exhaustive search for exotrojans using diverse observational techniques. In this work, we analyze the radial velocity time series informed by transits, focusing the search around low-mass stars.<i>Methods.<i/> We employed the <i>α<i/>-test method on confirmed planets searching for shifts between spectral and photometric mid-transit times. This technique is sensitive to mass imbalances within the planetary orbit, allowing us to identify non-negligible co-orbital masses.<i>Results.<i/> Among the 95 transiting planets examined, we find one robust exotrojan candidate with a significant 3-σ detection. Additionally, 25 exoplanets show compatibility with the presence of exotrojan companions at a 1-<i>σ<i/> level, requiring further observations to better constrain their presence. For two of those weak candidates, we find dimmings in their light curves within the predicted Lagrangian region. We established upper limits on the co-orbital masses for either the candidates and null detections.<i>Conclusions.<i/> Our analysis reveals that current high-resolution spectrographs effectively rule out co-orbitals more massive than Saturn around low-mass stars. This work points out to dozens of targets that have the potential to better constraint their exotrojan upper mass limit with dedicated radial velocity observations. We also explored the potential of observing the secondary eclipses of the confirmed exoplanets in our sample to enhance the exotrojan search, ultimately leading to a more accurate estimation of the occurrence rate of exotrojans.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131016","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 : 2024-08-30DOI: 10.1051/0004-6361/202451289
F. Lelli
Some gas-rich “ultra-diffuse” galaxies (UDGs), which are extreme examples of low surface brightness (LSB) dwarf galaxies, have been reported to lack dark matter and to be offset from the baryonic Tully–Fisher relation (BTFR). If confirmed, these UDGs would represent a serious challenge for both ΛCDM galaxy-formation models and Milgromian dynamics. Here I demonstrate that these conclusions are very dubious due to underestimated uncertainties on inclinations and/or distances. First, I show that UDGs are offset from the BTFR in the same way as usual face-on LSB dwarfs due to systematic biases at low inclinations. Next, I analyze the two UDGs with the best available rotation-curve data. The first (AGC 242019) is ideally inclined for kinematic studies; MOND can fit the observed rotation curve with a distance of 12.5 ± 0.6 Mpc, which is consistent with Virgocentric flow models. The second UDG (AGC 114905) is close to face-on, so not ideal for kinematic studies; MOND can fit the observed rotation curve with a distance of 68 ± 13 Mpc and inclination of 15° ±2°, which are consistent with existing data. In particular, I show that the disk inclination is more uncertain than previously estimated due to significant asymmetries (lopsidedness) in the stellar distribution. In conclusion, there is no strong evidence that gas-rich UDGs and gas-rich LSB dwarfs are distinct galaxy populations with different dynamical properties; instead, UDGs seem to be a subset of LSB dwarf galaxies biased toward face-on systems.
{"title":"Gas-rich “ultra-diffuse” galaxies are consistent with the baryonic Tully–Fisher relation and with Milgromian dynamics","authors":"F. Lelli","doi":"10.1051/0004-6361/202451289","DOIUrl":"https://doi.org/10.1051/0004-6361/202451289","url":null,"abstract":"Some gas-rich “ultra-diffuse” galaxies (UDGs), which are extreme examples of low surface brightness (LSB) dwarf galaxies, have been reported to lack dark matter and to be offset from the baryonic Tully–Fisher relation (BTFR). If confirmed, these UDGs would represent a serious challenge for both ΛCDM galaxy-formation models and Milgromian dynamics. Here I demonstrate that these conclusions are very dubious due to underestimated uncertainties on inclinations and/or distances. First, I show that UDGs are offset from the BTFR in the same way as usual face-on LSB dwarfs due to systematic biases at low inclinations. Next, I analyze the two UDGs with the best available rotation-curve data. The first (AGC 242019) is ideally inclined for kinematic studies; MOND can fit the observed rotation curve with a distance of 12.5 ± 0.6 Mpc, which is consistent with Virgocentric flow models. The second UDG (AGC 114905) is close to face-on, so not ideal for kinematic studies; MOND can fit the observed rotation curve with a distance of 68 ± 13 Mpc and inclination of 15° ±2°, which are consistent with existing data. In particular, I show that the disk inclination is more uncertain than previously estimated due to significant asymmetries (lopsidedness) in the stellar distribution. In conclusion, there is no strong evidence that gas-rich UDGs and gas-rich LSB dwarfs are distinct galaxy populations with different dynamical properties; instead, UDGs seem to be a subset of LSB dwarf galaxies biased toward face-on systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118094","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 : 2024-08-30DOI: 10.1051/0004-6361/202451166
M. J. Maureira, J. E. Pineda, H. B. Liu, L. Testi, D. Segura-Cox, C. Chandler, D. Johnstone, P. Caselli, G. Sabatini, Y. Aikawa, E. Bianchi, C. Codella, N. Cuello, D. Fedele, R. Friesen, L. Loinard, L. Podio, C. Ceccarelli, N. Sakai, S. Yamamoto
Context. Planets form in the disks surrounding young stars. The time at which the planet formation process begins is still an open question. Annular substructures such as rings and gaps in disks are intertwined with planet formation, and thus their presence or absence is commonly used to investigate the onset of this process.Aims. Current observations show that a limited number of disks surrounding protostars exhibit annular substructures, all of them in the Class I stage. The lack of observed features in most of these sources may indicate a late emergence of substructures, but it could also be an artifact of these disks being optically thick. To mitigate the problem of optical depth, we investigated substructures within a very young Class 0 disk characterized by low inclination using observations at longer wavelengths.Methods. We used 3 mm ALMA observations tracing dust emission at a resolution of 7 au to search for evidence of annular substructures in the disk around the deeply embedded Class 0 protostar Oph A SM1.Results. The observations reveal a nearly face-on disk (inclination ∼ 16°) extending up to 40 au. The radial intensity profile shows a clear deviation from a smooth profile near 30 au, which we interpret as the presence of either a gap at 28 au or a ring at 34 au with Gaussian widths of au and au, respectively. Crucially, the 3 mm emission at the location of the possible gap or ring is determined to be optically thin, precluding the possibility that this feature in the intensity profile is due to the emission being optically thick.Conclusions. Annular substructures resembling those in the more evolved Class I and II disks could indeed be present in the Class 0 stage, which is earlier than suggested by previous observations. Similar observations of embedded disks in which the high-optical-depth problem can be mitigated are clearly needed to better constrain the onset of substructures in the embedded stages.
背景行星在年轻恒星周围的星盘中形成。行星形成过程的开始时间仍是一个未决问题。环状亚结构（如星环和星盘中的空隙）与行星的形成息息相关，因此它们的存在与否通常被用来研究这一过程的开始时间。目前的观测结果表明，原恒星周围数量有限的星盘呈现出环状亚结构，所有这些星盘都处于一级阶段。在这些星源中，大部分都没有观测到亚结构的特征，这可能表明亚结构出现得较晚，但也可能是由于这些星盘的光学厚度较厚造成的。为了缓解光学深度的问题，我们利用较长波长的观测数据研究了一个非常年轻的0级盘内的亚结构，其特点是倾角较低。我们使用分辨率为 7 au 的 3 mm ALMA 观测数据追踪尘埃发射，以寻找深嵌在 0 级原恒星 Oph A SM1 周围的圆盘中环状亚结构的证据。观测结果显示，一个几乎面朝上的圆盘（倾角∼ 16°）一直延伸到 40 au。径向强度曲线在 30 au 附近明显偏离了平滑曲线，我们将其解释为在 28 au 处存在一个缺口，或者在 34 au 处存在一个高斯宽度分别为 au 和 au 的环。最重要的是，在可能的间隙或环的位置上的 3 毫米发射被确定为光学稀薄的，排除了强度曲线上的这一特征是由于发射是光学厚的这一可能性。与进化程度较高的 I 类和 II 类磁盘中的环状子结构相似的环状子结构确实可能存在于 0 类阶段，这比之前的观测结果所显示的时间要早。为了更好地确定嵌入阶段亚结构的出现时间，显然需要对嵌入盘进行类似的观测，以缓解高光学深度问题。
{"title":"FAUST","authors":"M. J. Maureira, J. E. Pineda, H. B. Liu, L. Testi, D. Segura-Cox, C. Chandler, D. Johnstone, P. Caselli, G. Sabatini, Y. Aikawa, E. Bianchi, C. Codella, N. Cuello, D. Fedele, R. Friesen, L. Loinard, L. Podio, C. Ceccarelli, N. Sakai, S. Yamamoto","doi":"10.1051/0004-6361/202451166","DOIUrl":"https://doi.org/10.1051/0004-6361/202451166","url":null,"abstract":"<i>Context.<i/> Planets form in the disks surrounding young stars. The time at which the planet formation process begins is still an open question. Annular substructures such as rings and gaps in disks are intertwined with planet formation, and thus their presence or absence is commonly used to investigate the onset of this process.<i>Aims.<i/> Current observations show that a limited number of disks surrounding protostars exhibit annular substructures, all of them in the Class I stage. The lack of observed features in most of these sources may indicate a late emergence of substructures, but it could also be an artifact of these disks being optically thick. To mitigate the problem of optical depth, we investigated substructures within a very young Class 0 disk characterized by low inclination using observations at longer wavelengths.<i>Methods.<i/> We used 3 mm ALMA observations tracing dust emission at a resolution of 7 au to search for evidence of annular substructures in the disk around the deeply embedded Class 0 protostar Oph A SM1.<i>Results.<i/> The observations reveal a nearly face-on disk (inclination ∼ 16°) extending up to 40 au. The radial intensity profile shows a clear deviation from a smooth profile near 30 au, which we interpret as the presence of either a gap at 28 au or a ring at 34 au with Gaussian widths of au and au, respectively. Crucially, the 3 mm emission at the location of the possible gap or ring is determined to be optically thin, precluding the possibility that this feature in the intensity profile is due to the emission being optically thick.<i>Conclusions.<i/> Annular substructures resembling those in the more evolved Class I and II disks could indeed be present in the Class 0 stage, which is earlier than suggested by previous observations. Similar observations of embedded disks in which the high-optical-depth problem can be mitigated are clearly needed to better constrain the onset of substructures in the embedded stages.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118095","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 : 2024-08-30DOI: 10.1051/0004-6361/202449884
David Benisty
The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×1012M⊙. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×1012M⊙. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. The combined result shows, for the first time, that a lower mass estimate can be obtained from the TA, with a consistent embedding and other systematic effects, and without an additional dark matter halo around the galaxies.
本星系群（LG）的动力学，尤其是银河系（MW）和仙女座星系（M 31）的动力学，对暗能量的存在非常敏感。这项工作把局域群看作是一个在完全Λ冷暗物质（ΛCDM）背景下的均质和各向同性膨胀时空中的双体问题，从而分析了局域群的演化。利用将LG动力学与LG质量联系起来的时序论证（TA），我们发现完整的ΛCDM背景预言的LG质量要低∼10%；而单独的Λ预言的LG质量要高∼10%。TA的质量是通过（i）模拟和（ii）大麦哲伦云（LMC）的影响来修正的，以减轻对M 31和MW内部质量分布、它们的时间演化以及它们之间未知的暗物质分布的约束。首先，利用IllustrisTNG模拟，我们考虑了两个扩展光环及其环境（而不是点粒子）的影响，并预测了它们的质量（3.89±0.62）×1012 M⊙。其次，LMC有效地改变了M 31向MW的分离和速度，并将预测质量降低到（2.33±0.72）×1012 M⊙。尽管这些星系之间的暗物质存在不确定性，但总体估计质量与MW和M 31的质量之和是一致的。TA的总质量与其他估计值相吻合，比如哈勃流和其他矮星系的室温定理。综合结果首次表明，在嵌入和其他系统效应保持一致的情况下，并且在星系周围没有额外暗物质晕的情况下，可以从 TA 得到较低的质量估计值。
{"title":"Weighing Milky Way and Andromeda in an expanding ΛCDM Universe","authors":"David Benisty","doi":"10.1051/0004-6361/202449884","DOIUrl":"https://doi.org/10.1051/0004-6361/202449884","url":null,"abstract":"The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. The combined result shows, for the first time, that a lower mass estimate can be obtained from the TA, with a consistent embedding and other systematic effects, and without an additional dark matter halo around the galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118129","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 : 2024-08-30DOI: 10.1051/0004-6361/202449829
A. A. C. Sander, J.-C. Bouret, M. Bernini-Peron, J. Puls, F. Backs, S. R. Berlanas, J. M. Bestenlehner, S. A. Brands, A. Herrero, F. Martins, O. Maryeva, D. Pauli, V. Ramachandran, P. A. Crowther, V. M. A. Gómez-González, A. C. Gormaz-Matamala, W.-R. Hamann, D. J. Hillier, R. Kuiper, C. J. K. Larkin, R. R. Lefever, A. Mehner, F. Najarro, L. M. Oskinova, E. C. Schösser, T. Shenar, H. Todt, A. ud-Doula, J. S. Vink
Context. The spectral analysis of hot, massive stars is a fundamental astrophysical method of determining their intrinsic properties and feedback. With their inherent, radiation-driven winds, the quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment in order to obtain the best solution within a given framework.Aims. We present an overview of different techniques for the quantitative spectroscopy of hot stars employed within the X-Shooting ULLYSES collaboration, ranging from grid-based approaches to tailored spectral fits. By performing a blind test for selected targets, we gain an overview of the similarities and differences between the resulting stellar and wind parameters. Our study is not a systematic benchmark between different codes or methods; our aim is to provide an overview of the parameter spread caused by different approaches.Methods. For three different stars from the XShooting ULLYSES sample (SMC O5 star AzV 377, LMC O7 star Sk -69° 50, and LMC O9 star Sk-66° 171), we employ different stellar atmosphere codes (CMFGEN, Fastwind, PoWR) and different strategies to determine their best-fitting model solutions. For our analyses, UV and optical spectroscopy are used to derive the stellar and wind properties with some methods relying purely on optical data for comparison. To determine the overall spectral energy distribution, we further employ additional photometry from the literature.Results. The effective temperatures found for each of the three different sample stars agree within 3 kK, while the differences in log g can be up to 0.2 dex. Luminosity differences of up to 0.1 dex result from different reddening assumptions, which seem to be systematically larger for the methods employing a genetic algorithm. All sample stars are found to be enriched in nitrogen. The terminal wind velocities are surprisingly similar and do not strictly follow the u∞−Teff relation.Conclusions. We find reasonable agreement in terms of the derived stellar and wind parameters between the different methods. Tailored fitting methods tend to be able to minimize or avoid discrepancies obtained with coarser or increasingly automatized treatments. The inclusion of UV spectral data is essential for the determination of realistic wind parameters. For one target (Sk -69° 50), we find clear indications of an evolved status.
{"title":"X-Shooting ULLYSES: Massive stars at low metallicity","authors":"A. A. C. Sander, J.-C. Bouret, M. Bernini-Peron, J. Puls, F. Backs, S. R. Berlanas, J. M. Bestenlehner, S. A. Brands, A. Herrero, F. Martins, O. Maryeva, D. Pauli, V. Ramachandran, P. A. Crowther, V. M. A. Gómez-González, A. C. Gormaz-Matamala, W.-R. Hamann, D. J. Hillier, R. Kuiper, C. J. K. Larkin, R. R. Lefever, A. Mehner, F. Najarro, L. M. Oskinova, E. C. Schösser, T. Shenar, H. Todt, A. ud-Doula, J. S. Vink","doi":"10.1051/0004-6361/202449829","DOIUrl":"https://doi.org/10.1051/0004-6361/202449829","url":null,"abstract":"<i>Context.<i/> The spectral analysis of hot, massive stars is a fundamental astrophysical method of determining their intrinsic properties and feedback. With their inherent, radiation-driven winds, the quantitative spectroscopy for hot, massive stars requires detailed numerical modeling of the atmosphere and an iterative treatment in order to obtain the best solution within a given framework.<i>Aims.<i/> We present an overview of different techniques for the quantitative spectroscopy of hot stars employed within the X-Shooting ULLYSES collaboration, ranging from grid-based approaches to tailored spectral fits. By performing a blind test for selected targets, we gain an overview of the similarities and differences between the resulting stellar and wind parameters. Our study is not a systematic benchmark between different codes or methods; our aim is to provide an overview of the parameter spread caused by different approaches.<i>Methods.<i/> For three different stars from the XShooting ULLYSES sample (SMC O5 star AzV 377, LMC O7 star Sk -69° 50, and LMC O9 star Sk-66° 171), we employ different stellar atmosphere codes (CMFGEN, Fastwind, PoWR) and different strategies to determine their best-fitting model solutions. For our analyses, UV and optical spectroscopy are used to derive the stellar and wind properties with some methods relying purely on optical data for comparison. To determine the overall spectral energy distribution, we further employ additional photometry from the literature.<i>Results.<i/> The effective temperatures found for each of the three different sample stars agree within 3 kK, while the differences in log <i>g<i/> can be up to 0.2 dex. Luminosity differences of up to 0.1 dex result from different reddening assumptions, which seem to be systematically larger for the methods employing a genetic algorithm. All sample stars are found to be enriched in nitrogen. The terminal wind velocities are surprisingly similar and do not strictly follow the <i>u<i/><sub>∞<sub/>−<i>T<i/><sub>eff<sub/> relation.<i>Conclusions.<i/> We find reasonable agreement in terms of the derived stellar and wind parameters between the different methods. Tailored fitting methods tend to be able to minimize or avoid discrepancies obtained with coarser or increasingly automatized treatments. The inclusion of UV spectral data is essential for the determination of realistic wind parameters. For one target (Sk -69° 50), we find clear indications of an evolved status.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118096","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 : 2024-08-30DOI: 10.1051/0004-6361/202451170
Johannes Buchner
The gas reservoir of galaxies can be altered by outflows that are driven by star formation and luminous active galactic nuclei. Jets heating the surroundings of host galaxies can also prevent the gas from cooling and prevent inflows. Spectacular examples for these three mass-displacement channels have been observed, but their importance in transforming the galaxy population depends on the occurrence rates of the outflow triggers. We investigate the absolute and relative importance of these three channels. In an observation-driven approach, we combined distribution functions and scaling relations to empirically compare average outflow rates across the total stellar mass spectrum of the galaxy and across cosmic time. This hinges on local outflow studies, which should be extended to systematic, large, and diverse samples, and we did not consider a halo-heating effect by radiation-driven outflows so far. Independent of simulations, our results show the dominance of star formation-driven outflows in low-mass galaxies. Massive galaxies today are predominately prevented from growing further by jet heating, while at z = 1 − 3, all three processes are approximately similarly important. Over the full mass spectrum and cosmic history, outflows driven by the radiation from active galactic nuclei are never the dominant process.
由恒星形成和发光的活动星系核驱动的外流可以改变星系的气体库。加热宿主星系周围环境的射流也会阻止气体冷却，防止气体流入。我们已经观测到了这三种质量位移通道的显著例子，但它们在改变星系群方面的重要性取决于外流触发因素的发生率。我们研究了这三种通道的绝对重要性和相对重要性。在观测驱动的方法中，我们结合了分布函数和比例关系，根据经验比较了星系总恒星质量谱和整个宇宙时间的平均外流率。这取决于对局部外流的研究，而这种研究应该扩展到系统的、大型的和多样化的样本中，而且我们迄今为止还没有考虑过辐射驱动的外流所产生的晕热效应。与模拟无关，我们的结果表明恒星形成驱动的外流在低质量星系中占主导地位。现在的大质量星系主要是通过喷流加热来阻止进一步增长的，而在 z = 1 - 3 时，这三个过程的重要性大致相同。在整个质量谱和宇宙历史中，由活动星系核辐射驱动的外流从来都不是主要过程。
{"title":"Impediments to the cosmic growth of galaxies: The outflow budget from Star Formation and Active Galactic Nuclei","authors":"Johannes Buchner","doi":"10.1051/0004-6361/202451170","DOIUrl":"https://doi.org/10.1051/0004-6361/202451170","url":null,"abstract":"The gas reservoir of galaxies can be altered by outflows that are driven by star formation and luminous active galactic nuclei. Jets heating the surroundings of host galaxies can also prevent the gas from cooling and prevent inflows. Spectacular examples for these three mass-displacement channels have been observed, but their importance in transforming the galaxy population depends on the occurrence rates of the outflow triggers. We investigate the absolute and relative importance of these three channels. In an observation-driven approach, we combined distribution functions and scaling relations to empirically compare average outflow rates across the total stellar mass spectrum of the galaxy and across cosmic time. This hinges on local outflow studies, which should be extended to systematic, large, and diverse samples, and we did not consider a halo-heating effect by radiation-driven outflows so far. Independent of simulations, our results show the dominance of star formation-driven outflows in low-mass galaxies. Massive galaxies today are predominately prevented from growing further by jet heating, while at <i>z<i/> = 1 − 3, all three processes are approximately similarly important. Over the full mass spectrum and cosmic history, outflows driven by the radiation from active galactic nuclei are never the dominant process.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118090","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 : 2024-08-30DOI: 10.1051/0004-6361/202450988
J. R. Goicoechea, J. Le Bourlot, J. H. Black, F. Alarcón, E. A. Bergin, O. Berné, E. Bron, A. Canin, E. Chapillon, R. Chown, E. Dartois, M. Gerin, E. Habart, T. J. Haworth, C. Joblin, O. Kannavou, F. Le Petit, T. Onaka, E. Peeters, J. Pety, E. Roueff, A. Sidhu, I. Schroetter, B. Tabone, A. G. G. M. Tielens, B. Trahin, D. Van De Putte, S. Vicente, M. Zannese
The gas-phase abundance of carbon, xC = [C/H]gas = xC+ + xC0 + xCO + … , and its depletion factors are essential parameters for understanding the gas and solid compositions that are ultimately incorporated into (exo)planets. The majority of protoplanetary disks are born in clusters and, as a result, are exposed to external far-ultraviolet (FUV) radiation. These FUV photons potentially affect the disk’s evolution, chemical composition, and line excitation. We present the first detection of the [C I] 609 μm fine-structure (3P1–3P0) line of neutral carbon (C0), achieved with ALMA, toward one of these disks, d203-506, in the Orion Nebula Cluster. We also report the detection of [C I] forbidden and C I permitted lines (from electronically excited states up to ∼10 eV) observed with JWST in the near-infrared (NIR). These lines trace the irradiated outer disk and photo-evaporative wind. Contrary to the common belief that these NIR lines are C+ recombination lines, we find that they are dominated by FUV-pumping of C0 followed by fluorescence cascades. They trace the transition from atomic to molecular gas, and their intensities scale with G0. The lack of outstanding NIR O I fluorescent emission, however, implies a sharper attenuation of external FUV radiation with E ≳ 12 eV (λ ≲ Lyman-β). This is related to a lower effective FUV dust absorption cross section compared to that of interstellar grains, implying a more prominent role for FUV shielding by the C0 photoionization continuum. The [C I] 609 μm line intensity is proportional to N(C0) and can be used to infer xC. We derive xC ≃ 1.4 × 10−4. This implies that there is no major depletion of volatile carbon compared to xC measured in the natal cloud, hinting at a young disk. We also show that external FUV radiation impacts the outer disk and wind by vertically shifting the water freeze-out depth, which likely results in less efficient grain growth and settling. This shift leads to nearly solar gas-phase C/O abundance ratios in these irradiated layers.
碳的气相丰度（xC = [C/H]gas = xC+ + xC0 + xCO + ...）及其耗竭因子是了解最终被纳入（外）行星的气体和固体成分的重要参数。大多数原行星盘诞生于星团中，因此会受到外部远紫外辐射（FUV）的影响。这些 FUV 光子可能会影响盘的演化、化学成分和激发线。我们利用 ALMA 首次探测到了猎户座星云星团中的一个中性碳（C0）的[C I] 609 μm 细结构（3P1-3P0）线，即 d203-506。我们还报告了利用 JWST 在近红外（NIR）观测到的[C I] 禁止和 C I 允许线（来自高达 ∼10 eV 的电子激发态）。这些谱线追踪了辐照外盘和光蒸发风。与一般认为这些近红外光线是C+重组线的观点相反，我们发现它们主要是由C0的FUV泵浦和荧光级联引起的。它们追溯了从原子气体到分子气体的转变过程，其强度与 G0 成比例。然而，由于缺乏突出的近红外 O I 荧光发射，这意味着 E ≳ 12 eV（λ ≲ Lyman-β）的外部 FUV 辐射衰减更为剧烈。这与尘埃的有效 FUV 吸收截面低于星际颗粒的吸收截面有关，意味着 C0 光离子化连续体对 FUV 的屏蔽作用更为突出。C I] 609 μm 线强度与 N(C0)成正比，可用来推断 xC。我们得出 xC ≃ 1.4 × 10-4。这意味着，与在原生云中测量到的 xC 相比，挥发性碳的消耗并不严重，这暗示了一个年轻的磁盘。我们还表明，外部 FUV 辐射通过垂直移动水的冻结深度来影响外盘和风，这可能会导致更低效率的晶粒生长和沉降。这种移动导致这些辐照层中的气相 C/O 丰度比接近太阳。
{"title":"PDRs4All","authors":"J. R. Goicoechea, J. Le Bourlot, J. H. Black, F. Alarcón, E. A. Bergin, O. Berné, E. Bron, A. Canin, E. Chapillon, R. Chown, E. Dartois, M. Gerin, E. Habart, T. J. Haworth, C. Joblin, O. Kannavou, F. Le Petit, T. Onaka, E. Peeters, J. Pety, E. Roueff, A. Sidhu, I. Schroetter, B. Tabone, A. G. G. M. Tielens, B. Trahin, D. Van De Putte, S. Vicente, M. Zannese","doi":"10.1051/0004-6361/202450988","DOIUrl":"https://doi.org/10.1051/0004-6361/202450988","url":null,"abstract":"The gas-phase abundance of carbon, <i>x<i/><sub>C<sub/> = [C/H]<sub>gas<sub/> = <i>x<i/><sub>C<sup>+<sup/><sub/> + <i>x<i/><sub>C<sup>0<sup/><sub/> + <i>x<i/><sub>CO<sub/> + … , and its depletion factors are essential parameters for understanding the gas and solid compositions that are ultimately incorporated into (exo)planets. The majority of protoplanetary disks are born in clusters and, as a result, are exposed to external far-ultraviolet (FUV) radiation. These FUV photons potentially affect the disk’s evolution, chemical composition, and line excitation. We present the first detection of the [C I] 609 μm fine-structure (<sup>3<sup/>P<sub>1<sub/>–<sup>3<sup/>P<sub>0<sub/>) line of neutral carbon (C<sup>0<sup/>), achieved with ALMA, toward one of these disks, d203-506, in the Orion Nebula Cluster. We also report the detection of [C I] forbidden and C I permitted lines (from electronically excited states up to ∼10 eV) observed with JWST in the near-infrared (NIR). These lines trace the irradiated outer disk and photo-evaporative wind. Contrary to the common belief that these NIR lines are C<sup>+<sup/> recombination lines, we find that they are dominated by FUV-pumping of C<sup>0<sup/> followed by fluorescence cascades. They trace the transition from atomic to molecular gas, and their intensities scale with <i>G<i/><sub>0<sub/>. The lack of outstanding NIR O I fluorescent emission, however, implies a sharper attenuation of external FUV radiation with <i>E<i/> ≳ 12 eV (<i>λ<i/> ≲ Lyman-<i>β<i/>). This is related to a lower effective FUV dust absorption cross section compared to that of interstellar grains, implying a more prominent role for FUV shielding by the C<sup>0<sup/> photoionization continuum. The [C I] 609 μm line intensity is proportional to <i>N<i/>(C<sup>0<sup/>) and can be used to infer <i>x<i/><sub>C<sub/>. We derive <i>x<i/><sub>C<sub/> ≃ 1.4 × 10<sup>−4<sup/>. This implies that there is no major depletion of volatile carbon compared to <i>x<i/><sub>C<sub/> measured in the natal cloud, hinting at a young disk. We also show that external FUV radiation impacts the outer disk and wind by vertically shifting the water freeze-out depth, which likely results in less efficient grain growth and settling. This shift leads to nearly solar gas-phase C/O abundance ratios in these irradiated layers.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118093","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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