Pub Date : 2023-10-01DOI: 10.3847/2041-8213/acf85a
Guochao Sun, Claude-André Faucher-Giguère, Christopher C. Hayward, Xuejian Shen, Andrew Wetzel, Rachel K. Cochrane
Abstract Recent discoveries of a significant population of bright galaxies at cosmic dawn z≳10 have enabled critical tests of cosmological galaxy formation models. In particular, the bright end of the galaxys’ UV luminosity functions (UVLFs) appear higher than predicted by many models. Using approximately 25,000 galaxy snapshots at 8 ≤ z ≤ 12 in a suite of FIRE-2 cosmological “zoom-in” simulations from the Feedback in Realistic Environments (FIRE) project, we show that the observed abundance of UV-bright galaxies at cosmic dawn is reproduced in these simulations with a multichannel implementation of standard stellar feedback processes, without any fine-tuning. Notably, we find no need to invoke previously suggested modifications, such as a nonstandard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. We contrast the UVLFs predicted by bursty star formation in these original simulations to those derived from star formation histories (SFHs) smoothed over prescribed timescales (e.g., 100 Myr). The comparison demonstrates that the strongly time-variable SFHs predicted by the FIRE simulations play a key role in correctly reproducing the observed, bright-end UVLFs at cosmic dawn: the bursty SFHs induce order-or-magnitude changes in the abundance of UV-bright ( M UV ≲ −20) galaxies at z ≳ 10. The predicted bright-end UVLFs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. We also find good agreement between the predicted and observationally inferred integrated UV luminosity densities, which evolve more weakly with redshift in FIRE than suggested by some other models.
{"title":"Bursty Star Formation Naturally Explains the Abundance of Bright Galaxies at Cosmic Dawn","authors":"Guochao Sun, Claude-André Faucher-Giguère, Christopher C. Hayward, Xuejian Shen, Andrew Wetzel, Rachel K. Cochrane","doi":"10.3847/2041-8213/acf85a","DOIUrl":"https://doi.org/10.3847/2041-8213/acf85a","url":null,"abstract":"Abstract Recent discoveries of a significant population of bright galaxies at cosmic dawn <?CDATA $left(zgtrsim 10right)$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mfenced close=\")\" open=\"(\"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>≳</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> have enabled critical tests of cosmological galaxy formation models. In particular, the bright end of the galaxys’ UV luminosity functions (UVLFs) appear higher than predicted by many models. Using approximately 25,000 galaxy snapshots at 8 ≤ z ≤ 12 in a suite of FIRE-2 cosmological “zoom-in” simulations from the Feedback in Realistic Environments (FIRE) project, we show that the observed abundance of UV-bright galaxies at cosmic dawn is reproduced in these simulations with a multichannel implementation of standard stellar feedback processes, without any fine-tuning. Notably, we find no need to invoke previously suggested modifications, such as a nonstandard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. We contrast the UVLFs predicted by bursty star formation in these original simulations to those derived from star formation histories (SFHs) smoothed over prescribed timescales (e.g., 100 Myr). The comparison demonstrates that the strongly time-variable SFHs predicted by the FIRE simulations play a key role in correctly reproducing the observed, bright-end UVLFs at cosmic dawn: the bursty SFHs induce order-or-magnitude changes in the abundance of UV-bright ( M UV ≲ −20) galaxies at z ≳ 10. The predicted bright-end UVLFs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. We also find good agreement between the predicted and observationally inferred integrated UV luminosity densities, which evolve more weakly with redshift in FIRE than suggested by some other models.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134933823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acf83c
Margot Boughelilba, Anita Reimer
Although Fanaroff-Riley (FR) type 0 radio galaxies are known to be the most numerous jet population in the local Universe, they are much less explored than the well-established class of FR I and FR II galaxies due to their intrinsic weakness. Observationally, their nuclear radio, optical and X-ray properties are comparable to the nuclear environment of FR Is. The recent detection of two FR 0s in the high-energy band suggests that like in FR Is, charged particles are accelerated there to energies that enable gamma-ray production. Up to now, only the lack of extended radio emission from FR 0s distinguishes them from FR Is. By comparing the spectral energy distribution of FR 0s with that of FR Is and in particular with that of M87 as a well-studied reference source of the FR I population, we find the broadband spectrum of FR 0s exceptionally close to M87's quiet core emission. Relying on that similarity, we apply a lepto-hadronic jet-accretion flow model to FR 0s. This model is able to explain the broadband spectral energy distribution, with parameters close to particle-field equipartition and matching all observational constraints. In this framework, FR 0s are multi-messenger jet sources, with a nature and highly magnetized environment similar to that of the naked quiet core of FR Is.
{"title":"On the Subparsec-scale Core Composition of FR 0 Radio Galaxies","authors":"Margot Boughelilba, Anita Reimer","doi":"10.3847/2041-8213/acf83c","DOIUrl":"https://doi.org/10.3847/2041-8213/acf83c","url":null,"abstract":"Although Fanaroff-Riley (FR) type 0 radio galaxies are known to be the most numerous jet population in the local Universe, they are much less explored than the well-established class of FR I and FR II galaxies due to their intrinsic weakness. Observationally, their nuclear radio, optical and X-ray properties are comparable to the nuclear environment of FR Is. The recent detection of two FR 0s in the high-energy band suggests that like in FR Is, charged particles are accelerated there to energies that enable gamma-ray production. Up to now, only the lack of extended radio emission from FR 0s distinguishes them from FR Is. By comparing the spectral energy distribution of FR 0s with that of FR Is and in particular with that of M87 as a well-studied reference source of the FR I population, we find the broadband spectrum of FR 0s exceptionally close to M87's quiet core emission. Relying on that similarity, we apply a lepto-hadronic jet-accretion flow model to FR 0s. This model is able to explain the broadband spectral energy distribution, with parameters close to particle-field equipartition and matching all observational constraints. In this framework, FR 0s are multi-messenger jet sources, with a nature and highly magnetized environment similar to that of the naked quiet core of FR Is.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134933874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfd1c
S. W. Good, O. K. Rantala, A.-S. M. Jylhä, C. H. K. Chen, C. Möstl, E. K. J. Kilpua
Abstract Interplanetary coronal mass ejections (ICMEs) have low proton beta across a broad range of heliocentric distances and a magnetic flux rope structure at large scales, making them a unique environment for studying solar wind fluctuations. Power spectra of magnetic field fluctuations in 28 ICMEs observed between 0.25 and 0.95 au by Solar Orbiter and Parker Solar Probe have been examined. At large scales, the spectra were dominated by power contained in the flux ropes. Subtraction of the background flux rope fields increased the mean spectral index from −5/3 to −3/2 at kd i ≤ 10 −3 . Rope subtraction also revealed shorter correlation lengths in the magnetic field. The spectral index was typically near −5/3 in the inertial range at all radial distances regardless of rope subtraction and steepened to values consistently below −3 with transition to kinetic scales. The high-frequency break point terminating the inertial range evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale, as expected for plasma at low proton beta. Magnetic compressibility at inertial scales did not show any significant correlation with radial distance, in contrast to the solar wind generally. In ICMEs, the distinctive spectral properties at injection scales appear mostly determined by the global flux rope structure while transition-kinetic properties are more influenced by the low proton beta; the intervening inertial range appears independent of both ICME features, indicative of a system-independent scaling of the turbulence.
{"title":"Turbulence Properties of Interplanetary Coronal Mass Ejections in the Inner Heliosphere: Dependence on Proton Beta and Flux Rope Structure","authors":"S. W. Good, O. K. Rantala, A.-S. M. Jylhä, C. H. K. Chen, C. Möstl, E. K. J. Kilpua","doi":"10.3847/2041-8213/acfd1c","DOIUrl":"https://doi.org/10.3847/2041-8213/acfd1c","url":null,"abstract":"Abstract Interplanetary coronal mass ejections (ICMEs) have low proton beta across a broad range of heliocentric distances and a magnetic flux rope structure at large scales, making them a unique environment for studying solar wind fluctuations. Power spectra of magnetic field fluctuations in 28 ICMEs observed between 0.25 and 0.95 au by Solar Orbiter and Parker Solar Probe have been examined. At large scales, the spectra were dominated by power contained in the flux ropes. Subtraction of the background flux rope fields increased the mean spectral index from −5/3 to −3/2 at kd i ≤ 10 −3 . Rope subtraction also revealed shorter correlation lengths in the magnetic field. The spectral index was typically near −5/3 in the inertial range at all radial distances regardless of rope subtraction and steepened to values consistently below −3 with transition to kinetic scales. The high-frequency break point terminating the inertial range evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale, as expected for plasma at low proton beta. Magnetic compressibility at inertial scales did not show any significant correlation with radial distance, in contrast to the solar wind generally. In ICMEs, the distinctive spectral properties at injection scales appear mostly determined by the global flux rope structure while transition-kinetic properties are more influenced by the low proton beta; the intervening inertial range appears independent of both ICME features, indicative of a system-independent scaling of the turbulence.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135762656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfe6e
Z. L. Yang, J. L. Han, W. C. Jing, W. Q. Su
Abstract PSR J1953+1844 (i.e., M71E) is a millisecond pulsar in a 53 minute binary orbit discovered by the Five-hundred-meter Aperture Spherical radio Telescope. The mass function from pulsar timing is 2.3 × 10 −7 M ⊙ . The possible redback origin of this system has been discussed by Pan et al. We discuss here an alternative evolution track for this binary system, namely that PSR J1953+1844 is a descendant of an ultracompact X-ray binary (UCXB), which has a hydrogen-poor donor accreting onto a neutron star (NS) with an orbital period of ≤1 hr. We noticed that some UCXB systems hold an accreting millisecond X-ray pulsar (AMXP) and a donor with a mass of about 0.01 M ⊙ . M71E has a very similar orbit to those of AMXPs, indicating that it might be evolved from a UCXB similar to PSR J1653–0158. The companion star of M71E should be significantly bloated and it most probably has a carbon and oxygen composition, otherwise a low inclination angle of the orbit is required for a helium companion. The discovery of this M71E binary system may shed light on when and how an NS in a UCXB turns into a radio pulsar.
PSR J1953+1844(即M71E)是500米口径球面射电望远镜在53分钟双星轨道上发现的一颗毫秒脉冲星。脉冲星计时的质量函数为2.3 × 10−7 M⊙。Pan等人讨论了该系统可能的红背起源。我们在这里讨论了这个双星系统的另一种演化轨迹，即PSR J1953+1844是一个超紧凑x射线双星(UCXB)的后代，它有一个贫氢的供体吸积到轨道周期≤1小时的中子星(NS)上。我们注意到一些UCXB系统拥有一个吸积的毫秒x射线脉冲星(AMXP)和一个质量约为0.01 M⊙的供体。M71E的轨道与amxp非常相似，这表明它可能是从类似于PSR J1653-0158的UCXB演变而来的。M71E的伴星应该是明显膨胀的，它很可能是由碳和氧组成的，否则一个氦伴星就需要一个低倾角的轨道。M71E双星系统的发现可能会揭示UCXB中的NS何时以及如何转变为射电脉冲星。
{"title":"PSR J1953+1844 Probably Being the Descendant of an Ultracompact X-Ray Binary","authors":"Z. L. Yang, J. L. Han, W. C. Jing, W. Q. Su","doi":"10.3847/2041-8213/acfe6e","DOIUrl":"https://doi.org/10.3847/2041-8213/acfe6e","url":null,"abstract":"Abstract PSR J1953+1844 (i.e., M71E) is a millisecond pulsar in a 53 minute binary orbit discovered by the Five-hundred-meter Aperture Spherical radio Telescope. The mass function from pulsar timing is 2.3 × 10 −7 M ⊙ . The possible redback origin of this system has been discussed by Pan et al. We discuss here an alternative evolution track for this binary system, namely that PSR J1953+1844 is a descendant of an ultracompact X-ray binary (UCXB), which has a hydrogen-poor donor accreting onto a neutron star (NS) with an orbital period of ≤1 hr. We noticed that some UCXB systems hold an accreting millisecond X-ray pulsar (AMXP) and a donor with a mass of about 0.01 M ⊙ . M71E has a very similar orbit to those of AMXPs, indicating that it might be evolved from a UCXB similar to PSR J1653–0158. The companion star of M71E should be significantly bloated and it most probably has a carbon and oxygen composition, otherwise a low inclination angle of the orbit is required for a helium companion. The discovery of this M71E binary system may shed light on when and how an NS in a UCXB turns into a radio pulsar.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"152 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135850948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfee9
Bob Jacobs, Jean-Michel Désert, Peter Gao, Caroline V. Morley, Jacob Arcangeli, Saugata Barat, Mark S. Marley, Julianne I. Moses, Jonathan J. Fortney, Jacob L. Bean, Kevin B. Stevenson, Vatsal Panwar
Abstract The presence of aerosols is intimately linked to the global energy budget and the composition of a planet’s atmosphere. Their ability to reflect incoming light prevents energy from being deposited into the atmosphere, and they shape the spectra of exoplanets. We observed five near-infrared secondary eclipses of WASP-80b with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope to provide constraints on the presence and properties of atmospheric aerosols. We detect a broadband eclipse depth of 34 ± 10 ppm for WASP-80b. We detect a higher planetary flux than expected from thermal emission alone at 1.6 σ , which hints toward the presence of reflecting aerosols on this planet’s dayside, indicating a geometric albedo of A g < 0.33 at 3 σ . We paired the WFC3 data with Spitzer data and explored multiple atmospheric models with and without aerosols to interpret this spectrum. Albeit consistent with a clear dayside atmosphere, we found a slight preference for near-solar metallicities and for dayside clouds over hazes. We exclude soot haze formation rates higher than 10 −10.7 g cm −2 s −1 and tholin formation rates higher than 10 −12.0 g cm −2 s −1 at 3 σ . We applied the same atmospheric models to a previously published WFC3/Spitzer transmission spectrum for this planet and found weak haze formation. A single soot haze formation rate best fits both the dayside and the transmission spectra simultaneously. However, we emphasize that no models provide satisfactory fits in terms of the chi-square of both spectra simultaneously, indicating longitudinal dissimilarity in the atmosphere’s aerosol composition.
气溶胶的存在与全球能量收支和行星大气组成密切相关。它们反射入射光的能力阻止了能量沉积到大气中，它们塑造了系外行星的光谱。我们利用哈勃太空望远镜上的宽视场相机3 (WFC3)观测了WASP-80b的5次近红外二次日食，以提供大气气溶胶存在和性质的约束条件。我们探测到WASP-80b的宽带日食深度为34±10 ppm。我们探测到的行星通量比仅从热发射中预期的要高，为1.6 σ，这暗示在这颗行星的日面存在反射气溶胶，表明a g <的几何反照率;在3 σ处为0.33。我们将WFC3的数据与斯皮策的数据配对，并探索了有或没有气溶胶的多种大气模型来解释这一光谱。尽管与晴朗的日面大气一致，但我们发现近太阳金属丰度和日面云比雾霾更有轻微的偏好。我们排除了在3 σ下大于10−10.7 g cm−2 s−1的烟灰霾形成率和大于10−12.0 g cm−2 s−1的噻吩形成率。我们将同样的大气模型应用于之前发表的WFC3/斯皮策透射光谱，发现了微弱的雾霾形成。单一的烟灰霾形成率最适合同时适应昼侧光谱和透射光谱。然而，我们强调，没有任何模式能同时提供令人满意的两种光谱的卡方拟合，这表明大气气溶胶成分的纵向差异。
{"title":"Probing Reflection from Aerosols with the Near-infrared Dayside Spectrum of WASP-80b","authors":"Bob Jacobs, Jean-Michel Désert, Peter Gao, Caroline V. Morley, Jacob Arcangeli, Saugata Barat, Mark S. Marley, Julianne I. Moses, Jonathan J. Fortney, Jacob L. Bean, Kevin B. Stevenson, Vatsal Panwar","doi":"10.3847/2041-8213/acfee9","DOIUrl":"https://doi.org/10.3847/2041-8213/acfee9","url":null,"abstract":"Abstract The presence of aerosols is intimately linked to the global energy budget and the composition of a planet’s atmosphere. Their ability to reflect incoming light prevents energy from being deposited into the atmosphere, and they shape the spectra of exoplanets. We observed five near-infrared secondary eclipses of WASP-80b with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope to provide constraints on the presence and properties of atmospheric aerosols. We detect a broadband eclipse depth of 34 ± 10 ppm for WASP-80b. We detect a higher planetary flux than expected from thermal emission alone at 1.6 σ , which hints toward the presence of reflecting aerosols on this planet’s dayside, indicating a geometric albedo of A g < 0.33 at 3 σ . We paired the WFC3 data with Spitzer data and explored multiple atmospheric models with and without aerosols to interpret this spectrum. Albeit consistent with a clear dayside atmosphere, we found a slight preference for near-solar metallicities and for dayside clouds over hazes. We exclude soot haze formation rates higher than 10 −10.7 g cm −2 s −1 and tholin formation rates higher than 10 −12.0 g cm −2 s −1 at 3 σ . We applied the same atmospheric models to a previously published WFC3/Spitzer transmission spectrum for this planet and found weak haze formation. A single soot haze formation rate best fits both the dayside and the transmission spectra simultaneously. However, we emphasize that no models provide satisfactory fits in terms of the chi-square of both spectra simultaneously, indicating longitudinal dissimilarity in the atmosphere’s aerosol composition.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"160 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135963551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acf577
Nikku Madhusudhan, Subhajit Sarkar, Savvas Constantinou, Måns Holmberg, Anjali A. A. Piette, Julianne I. Moses
Abstract The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet–star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H 2 -rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9–5.2 μ m range. The spectrum reveals strong detections of methane (CH 4 ) and carbon dioxide (CO 2 ) at 5 σ and 3 σ confidence, respectively, with high volume mixing ratios of ∼1% each in a H 2 -rich atmosphere. The abundant CH 4 and CO 2 , along with the nondetection of ammonia (NH 3 ), are consistent with chemical predictions for an ocean under a temperate H 2 -rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH 4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.
{"title":"Carbon-bearing Molecules in a Possible Hycean Atmosphere","authors":"Nikku Madhusudhan, Subhajit Sarkar, Savvas Constantinou, Måns Holmberg, Anjali A. A. Piette, Julianne I. Moses","doi":"10.3847/2041-8213/acf577","DOIUrl":"https://doi.org/10.3847/2041-8213/acf577","url":null,"abstract":"Abstract The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet–star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H 2 -rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9–5.2 μ m range. The spectrum reveals strong detections of methane (CH 4 ) and carbon dioxide (CO 2 ) at 5 σ and 3 σ confidence, respectively, with high volume mixing ratios of ∼1% each in a H 2 -rich atmosphere. The abundant CH 4 and CO 2 , along with the nondetection of ammonia (NH 3 ), are consistent with chemical predictions for an ocean under a temperate H 2 -rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH 4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135996810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acf933
Andrii Voshchepynets, Oleksiy V. Agapitov, Lynn Wilson, Vassilis Angelopoulos, Samer T. Alnussirat, Michael Balikhin, Myroslava Hlebena, Ihor Korol, Davin Larson, David Mitchell, Christopher Owen, Ali Rahmati
Abstract We present the results of processing the effects of the powerful gamma-ray burst GRB221009A captured by the charged particle detectors (electrostatic analyzers and solid-state detectors) on board spacecraft at different points in the heliosphere on 2022 October 9. To follow the GRB221009A propagation through the heliosphere, we used the electron and proton flux measurements from solar missions Solar Orbiter and STEREO-A; Earth’s magnetosphere and solar wind missions THEMIS and Wind; meteorological satellites POES15, POES19, and MetOp3; and MAVEN—a NASA mission orbiting Mars. GRB221009A had a structure of four bursts: the less intense Pulse 1—the triggering impulse—was detected by gamma-ray observatories at T 0 = 13:16:59 UT (near the Earth); the most intense Pulses 2 and 3 were detected on board all the spacecraft from the list; and Pulse 4 was detected in more than 500 s after Pulse 1. Due to their different scientific objectives, the spacecraft, whose data were used in this study, were separated by more than 1 au (Solar Orbiter and MAVEN). This enabled the tracking of GRB221009A as it was propagating across the heliosphere. STEREO-A was the first to register Pulse 2 and 3 of the GRB, almost 100 s before their detection by spacecraft in the vicinity of Earth. MAVEN detected GRB221009A Pulses 2, 3, and 4 at the orbit of Mars about 237 s after their detection near Earth. By processing the observed time delays, we show that the source location of the GRB221009A was at R.A. 288.°5, decl. 18.°5 ± 2° (J2000).
{"title":"Multipoint Detection of GRB221009A’s Propagation through the Heliosphere","authors":"Andrii Voshchepynets, Oleksiy V. Agapitov, Lynn Wilson, Vassilis Angelopoulos, Samer T. Alnussirat, Michael Balikhin, Myroslava Hlebena, Ihor Korol, Davin Larson, David Mitchell, Christopher Owen, Ali Rahmati","doi":"10.3847/2041-8213/acf933","DOIUrl":"https://doi.org/10.3847/2041-8213/acf933","url":null,"abstract":"Abstract We present the results of processing the effects of the powerful gamma-ray burst GRB221009A captured by the charged particle detectors (electrostatic analyzers and solid-state detectors) on board spacecraft at different points in the heliosphere on 2022 October 9. To follow the GRB221009A propagation through the heliosphere, we used the electron and proton flux measurements from solar missions Solar Orbiter and STEREO-A; Earth’s magnetosphere and solar wind missions THEMIS and Wind; meteorological satellites POES15, POES19, and MetOp3; and MAVEN—a NASA mission orbiting Mars. GRB221009A had a structure of four bursts: the less intense Pulse 1—the triggering impulse—was detected by gamma-ray observatories at T 0 = 13:16:59 UT (near the Earth); the most intense Pulses 2 and 3 were detected on board all the spacecraft from the list; and Pulse 4 was detected in more than 500 s after Pulse 1. Due to their different scientific objectives, the spacecraft, whose data were used in this study, were separated by more than 1 au (Solar Orbiter and MAVEN). This enabled the tracking of GRB221009A as it was propagating across the heliosphere. STEREO-A was the first to register Pulse 2 and 3 of the GRB, almost 100 s before their detection by spacecraft in the vicinity of Earth. MAVEN detected GRB221009A Pulses 2, 3, and 4 at the orbit of Mars about 237 s after their detection near Earth. By processing the observed time delays, we show that the source location of the GRB221009A was at R.A. 288.°5, decl. 18.°5 ± 2° (J2000).","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134937019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Abstract Transferring a significant fraction of the magnetic flux from a dense cloud core is essential in the star formation process. A ringlike structure produced by magnetic flux loss has been predicted theoretically, but no observational identification has been presented. We have performed ALMA observations of the Class I protostar IRS 2 in the Corona Australis star-forming region and resolved a distinctive gas ring in the C 18 O ( J = 2–1) line emission. The center of this gas ring is ∼5000 au away from the protostar, with a diameter of ∼7000 au. The radial velocity of the gas is ≲ 1 km s −1 blueshifted from that of the protostar, with a possible expanding feature judged from the velocity-field (moment 1) map and position–velocity diagram. These features are either observationally new or have been discovered but not discussed in depth because they are difficult to explain by well-studied protostellar phenomena such as molecular outflows and accretion streamers. A plausible interpretation is a magnetic wall created by the advection of magnetic flux, which is theoretically expected in the Class 0/I phase during star formation as a removal mechanism of magnetic flux. Similar structures reported in the other young stellar sources could likely be candidates formed by the same mechanism, encouraging us to revisit the issue of magnetic flux transport in the early stages of star formation from an observational perspective.
在恒星形成过程中，从致密云核转移相当一部分磁通量是必不可少的。磁通损失产生的环状结构已在理论上得到了预测，但尚未提出观测鉴定。我们对南冕恒星形成区的I类原恒星IRS 2进行了ALMA观测，并在c18o (J = 2 - 1)线发射中发现了一个独特的气体环。这个气体环的中心距离原恒星约5000天文单位，直径约7000天文单位。从速度场(矩1)图和位置速度图判断，该气体的径向速度与原恒星的径向速度相差小于1 km s−1，具有可能的膨胀特征。这些特征要么是观测上的新发现，要么是已经发现的，但没有深入讨论，因为它们很难用研究得很好的原恒星现象(如分子外流和吸积流光)来解释。一种合理的解释是由磁通量平流产生的磁壁，理论上预计在恒星形成期间的0/I类阶段作为磁通量的消除机制。在其他年轻恒星源中报道的类似结构可能是由相同机制形成的候选者，这鼓励我们从观测的角度重新审视恒星形成早期阶段的磁通量传输问题。
{"title":"An ALMA-resolved View of 7000 au Protostellar Gas Ring around the Class I Source CrA-IRS 2 as a Possible Sign of Magnetic Flux Advection","authors":"Kazuki Tokuda, Naofumi Fukaya, Kengo Tachihara, Mitsuki Omura, Naoto Harada, Shingo Nozaki, Ayumu Shoshi, Masahiro N. Machida","doi":"10.3847/2041-8213/acfca9","DOIUrl":"https://doi.org/10.3847/2041-8213/acfca9","url":null,"abstract":"Abstract Transferring a significant fraction of the magnetic flux from a dense cloud core is essential in the star formation process. A ringlike structure produced by magnetic flux loss has been predicted theoretically, but no observational identification has been presented. We have performed ALMA observations of the Class I protostar IRS 2 in the Corona Australis star-forming region and resolved a distinctive gas ring in the C 18 O ( J = 2–1) line emission. The center of this gas ring is ∼5000 au away from the protostar, with a diameter of ∼7000 au. The radial velocity of the gas is ≲ 1 km s −1 blueshifted from that of the protostar, with a possible expanding feature judged from the velocity-field (moment 1) map and position–velocity diagram. These features are either observationally new or have been discovered but not discussed in depth because they are difficult to explain by well-studied protostellar phenomena such as molecular outflows and accretion streamers. A plausible interpretation is a magnetic wall created by the advection of magnetic flux, which is theoretically expected in the Class 0/I phase during star formation as a removal mechanism of magnetic flux. Similar structures reported in the other young stellar sources could likely be candidates formed by the same mechanism, encouraging us to revisit the issue of magnetic flux transport in the early stages of star formation from an observational perspective.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135607004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfd1d
Yoonyoung Kim, David Jewitt
Abstract The collision of the NASA DART spacecraft with asteroid Dimorphos resulted in the formation of a distinctive and long-lived debris trail, formed by the action of solar radiation pressure on ejected particles. This trail briefly displayed a double appearance, which has been interpreted as the result of a double ejection. We present a model that can produce a transient double trail without the need to assume a double ejection. Our model explains the appearance of the double trail as a projection of the cone walls when viewed from a large angle to the cone axis and avoids the problem of producing dust in two epochs from a single, instantaneous impact. The particles follow a broken power-law size distribution, with differential indices q = 2.7 ± 0.2 (1 μ m ≤ a ≤ 2 mm), 3.9 ± 0.1 (2 mm < a ≤ 1 cm), and 4.2 ± 0.2 (1 cm < a ≤ 20 cm). We find that the total trail mass in particles from 1 μ m to 20 cm in size (for an assumed density 3500 kg m −3 ) is ∼1.7 × 10 7 kg, rising to 2.2 × 10 7 kg, when extended to boulders up to 3.5 m in radius. This corresponds to 0.4%–0.6% of the mass of Dimorphos.
美国宇航局DART航天器与小行星Dimorphos的碰撞导致形成了一条独特且长寿命的碎片轨迹，这是由太阳辐射压力对喷射粒子的作用形成的。这条轨迹短暂地呈现出双重外观，这被解释为双重喷射的结果。我们提出了一个可以产生瞬态双尾的模型，而不需要假设双弹射。我们的模型解释了双轨迹的外观，当从大角度观察到锥轴时，作为锥壁的投影，并避免了单一瞬时撞击在两个时期产生灰尘的问题。颗粒粒径呈幂律破碎分布，微分指数q = 2.7±0.2 (1 μ m≤a≤2 mm)， 3.9±0.1 (2 mm <A≤1cm)， 4.2±0.2 (1cm <A≤20cm)。我们发现，1 μ m到20 cm大小的颗粒(假设密度为3500 kg m - 3)的总尾迹质量为1.7 × 10.7 kg，当扩展到半径为3.5 m的巨石时，尾迹质量上升到2.2 × 10.7 kg。这相当于Dimorphos质量的0.4%-0.6%。
{"title":"A Single Ejection Model of the DART/Dimorphos Debris Trail","authors":"Yoonyoung Kim, David Jewitt","doi":"10.3847/2041-8213/acfd1d","DOIUrl":"https://doi.org/10.3847/2041-8213/acfd1d","url":null,"abstract":"Abstract The collision of the NASA DART spacecraft with asteroid Dimorphos resulted in the formation of a distinctive and long-lived debris trail, formed by the action of solar radiation pressure on ejected particles. This trail briefly displayed a double appearance, which has been interpreted as the result of a double ejection. We present a model that can produce a transient double trail without the need to assume a double ejection. Our model explains the appearance of the double trail as a projection of the cone walls when viewed from a large angle to the cone axis and avoids the problem of producing dust in two epochs from a single, instantaneous impact. The particles follow a broken power-law size distribution, with differential indices q = 2.7 ± 0.2 (1 μ m ≤ a ≤ 2 mm), 3.9 ± 0.1 (2 mm < a ≤ 1 cm), and 4.2 ± 0.2 (1 cm < a ≤ 20 cm). We find that the total trail mass in particles from 1 μ m to 20 cm in size (for an assumed density 3500 kg m −3 ) is ∼1.7 × 10 7 kg, rising to 2.2 × 10 7 kg, when extended to boulders up to 3.5 m in radius. This corresponds to 0.4%–0.6% of the mass of Dimorphos.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135705700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2023-10-01DOI: 10.3847/2041-8213/acfaec
Amy J. Louca, Yamila Miguel, Daria Kubyshkina
Abstract The recent observations on WASP-39 b by JWST have revealed hints of high metallicity within the atmosphere compared to its host star. There are various theories on how these high metallic atmospheres emerge. In this study, we closely investigate the impact of extreme escape in the form of hydrodynamic escape to see its impact on atmospheric metallicity and spectral features such as CH 4 , CO 2 and SO 2 . We perform a grid simulation, with an adapted version of MESA that includes hydrodynamic escape to fully evolve planets with similar masses and radii to the currently observed WASP-39 b estimates. By making use of (photo)chemical kinetics and radiative transfer codes, we evaluate the transmission spectra at various time intervals throughout the simulation. Our results indicate that the massive size of WASP-39 b limits the metal enhancement to a maximum of ∼1.23× the initial metallicity. When incorporating metal drag, this enhancement factor is repressed to an even greater degree, resulting in an enrichment of at most ∼0.4%. As a consequence, when assuming an initial solar metallicity, metal-enriched spectral features like SO 2 are still missing after ∼9 Gyr into the simulation. This paper, thus, demonstrates that hydrodynamic escape cannot be the primary process behind the high metallicity observed in the atmosphere of WASP-39 b, suggesting instead that a metal-enhanced atmosphere was established during its formation.
{"title":"Metallicity and Spectral Evolution of WASP 39b: The Limited Role of Hydrodynamic Escape","authors":"Amy J. Louca, Yamila Miguel, Daria Kubyshkina","doi":"10.3847/2041-8213/acfaec","DOIUrl":"https://doi.org/10.3847/2041-8213/acfaec","url":null,"abstract":"Abstract The recent observations on WASP-39 b by JWST have revealed hints of high metallicity within the atmosphere compared to its host star. There are various theories on how these high metallic atmospheres emerge. In this study, we closely investigate the impact of extreme escape in the form of hydrodynamic escape to see its impact on atmospheric metallicity and spectral features such as CH 4 , CO 2 and SO 2 . We perform a grid simulation, with an adapted version of MESA that includes hydrodynamic escape to fully evolve planets with similar masses and radii to the currently observed WASP-39 b estimates. By making use of (photo)chemical kinetics and radiative transfer codes, we evaluate the transmission spectra at various time intervals throughout the simulation. Our results indicate that the massive size of WASP-39 b limits the metal enhancement to a maximum of ∼1.23× the initial metallicity. When incorporating metal drag, this enhancement factor is repressed to an even greater degree, resulting in an enrichment of at most ∼0.4%. As a consequence, when assuming an initial solar metallicity, metal-enriched spectral features like SO 2 are still missing after ∼9 Gyr into the simulation. This paper, thus, demonstrates that hydrodynamic escape cannot be the primary process behind the high metallicity observed in the atmosphere of WASP-39 b, suggesting instead that a metal-enhanced atmosphere was established during its formation.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"129 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135655570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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