Pub Date : 2024-10-15DOI: 10.3847/1538-4357/ad77c6
Zulema Abraham, Pedro P. B. Beaklini, Isabel Aleman, Raghvendra Sahai, Albert Zijlstra, Stavros Akras, Denise R. Gonçalves and Toshiya Ueta
The hydrogen recombination lines H30α, H40α, H42α, H50β, and H57γ and the underlying bremsstrahlung continuum emission were detected with ALMA in the bipolar nebula Mz3. The source was not spatially resolved, but the velocity profile of the H30α line shows clear indication of maser amplification, confirming previous reports of laser amplification in the far-infrared H recombination lines observed with Herschel Space Observatory. Comparison between the flux densities of the H50β, H40α, and H42α lines show overcooling, or darkness amplification by stimulated absorption (dasar effect) at the LSR velocity of about −25 km s−1, which constrains the density of the absorbing region to about 103 cm−3. The H30α line, on the other hand, presents maser lines at LSR velocities of −69 and −98 km s−1, which indicates ionized gas with densities close to 107 cm−3. Although the source of emission was not resolved, it was possible to find the central position of the images for each velocity interval, which resulted in a well defined position–velocity distribution.
利用ALMA在双极星云Mz3中探测到了氢重组线H30α、H40α、H42α、H50β和H57γ以及其下的轫致辐射。虽然没有对光源进行空间分辨，但 H30α 线的速度剖面显示出明显的 maser 放大迹象，这证实了之前关于赫歇尔空间天文台观测到的远红外 H 重组线激光放大的报告。H50β、H40α和H42α线的通量密度比较显示，在大约-25 km s-1的LSR速度下，存在过冷或受激吸收的黑暗放大现象（达萨效应），这将吸收区域的密度限制在大约103 cm-3。另一方面，H30α 线在 LSR 速度为 -69 和 -98 km s-1 时呈现出 maser 线，这表明电离气体的密度接近 107 cm-3。虽然没有分辨出发射源，但可以找到每个速度区间图像的中心位置，从而得到明确的位置-速度分布。
{"title":"ALMA Detection of Masers and Dasars in the Hydrogen Recombination Lines of the Planetary Nebula Mz3","authors":"Zulema Abraham, Pedro P. B. Beaklini, Isabel Aleman, Raghvendra Sahai, Albert Zijlstra, Stavros Akras, Denise R. Gonçalves and Toshiya Ueta","doi":"10.3847/1538-4357/ad77c6","DOIUrl":"https://doi.org/10.3847/1538-4357/ad77c6","url":null,"abstract":"The hydrogen recombination lines H30α, H40α, H42α, H50β, and H57γ and the underlying bremsstrahlung continuum emission were detected with ALMA in the bipolar nebula Mz3. The source was not spatially resolved, but the velocity profile of the H30α line shows clear indication of maser amplification, confirming previous reports of laser amplification in the far-infrared H recombination lines observed with Herschel Space Observatory. Comparison between the flux densities of the H50β, H40α, and H42α lines show overcooling, or darkness amplification by stimulated absorption (dasar effect) at the LSR velocity of about −25 km s−1, which constrains the density of the absorbing region to about 103 cm−3. The H30α line, on the other hand, presents maser lines at LSR velocities of −69 and −98 km s−1, which indicates ionized gas with densities close to 107 cm−3. Although the source of emission was not resolved, it was possible to find the central position of the images for each velocity interval, which resulted in a well defined position–velocity distribution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He iλ4471 and He iiλ4686 to He iλ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of ne ∼ 103−4 cm−3 much larger than local values at low O/H, . In contrast, we obtain low He/H and ne values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or ne–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.
我们介绍了三个詹姆斯-韦伯太空望远镜星系（GS-NDG-9422、RXCJ2248-ID和GLASS150008）的He i/Hβ通量和He/H丰度比，这些星系对N/O丰度比具有重要的约束，其z∼ 6的光谱覆盖范围从He iλ4471 和He iiλ4686 到He iλ7065，并与68个本地矮星系进行了比较。我们发现，这些高兹星系有很强的 He i 辐射，He i/Hβ 通量比普遍大于本地矮星系。我们利用所有探测到的 Hei、He ii 和 2-3 条氢巴尔默线推导出 He/H，其方法与为宇宙学研究而进行的本地 He/H 测定相同。这些高赫兹星系显示出 He/H ≳0.10 的过量或 ne ∼ 103-4 cm-3 的高电子密度，远大于低 O/H 时的本地值。与此相反，我们用同样的技术和同样的氦线和氢线得到了本地矮星系的低He/H和ne值，证实了高兹星系和本地矮星系之间的差异不是由系统学模拟的。虽然没有明确得出(1)氦过剩和(2)电子密度过高这两种情况的结论，但我们发现通过对比高兹星系和本地矮星系，氦/氢-N/O平面或氖-N/O平面之间存在正相关。方案（1）表明，过量的氦和氮不是由核心坍缩超新星的标准化学富集来解释的，而是分别由CNO循环产物和平衡比来解释的。方案（2）表明，强氦线源自高兹星系中心致密云的过度碰撞激发。
{"title":"Strong He i Emission Lines in High N/O Galaxies at z ∼ 6 Identified in JWST Spectra: High He/H Abundance Ratios or High Electron Densities?","authors":"Hiroto Yanagisawa, Masami Ouchi, Kuria Watanabe, Akinori Matsumoto, Kimihiko Nakajima, Hidenobu Yajima, Kentaro Nagamine, Koh Takahashi, Minami Nakane, Nozomu Tominaga, Hiroya Umeda, Hajime Fukushima, Yuichi Harikane, Yuki Isobe, Yoshiaki Ono, Yi Xu and Yechi Zhang","doi":"10.3847/1538-4357/ad72ec","DOIUrl":"https://doi.org/10.3847/1538-4357/ad72ec","url":null,"abstract":"We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He iλ4471 and He iiλ4686 to He iλ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of ne ∼ 103−4 cm−3 much larger than local values at low O/H, . In contrast, we obtain low He/H and ne values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or ne–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.3847/1538-4357/ad701d
Luis A. Zapata, Manuel Fernández-López, Patricio Sanhueza, Josep M. Girart, Luis F. Rodríguez, Paulo Cortés, Patrick Koch, Maria T. Beltrán, Kate Pattle, Henrik Beuther, Piyali Saha, Wenyu Jiao, Fengwei Xu, Xing Walker Lu, Fernando Olguin, Shanghuo Li, Ian W. Stephens, Ji-hyun Kang, Yu Cheng, Spandan Choudhury, Kaho Morii, Eun Jung Chung, Jia-Wei Wang, Jihye Hwang, A-Ran Lyo, Q. Zhang and Huei-Ru Vivien Chen
The formation of the massive stars, and in particular, the role that the magnetic fields play in their early evolutionary phase is still far from being completely understood. Here, we present the Atacama Large Millimeter/submillimeter Array 1.2 mm full polarized continuum and H13CO+(3−2), CS(5−4), and HN13C(3−2) line observations with a high angular resolution (∼0.″4 or 1100 au). In the 1.2 mm continuum emission, we reveal a dusty envelope surrounding the massive protostars, IRAS16547-E and IRAS16547-W, with dimensions of ∼10,000 au. This envelope has a biconical structure likely carved by the powerful thermal radio jet present in region. The magnetic field vectors follow very well the biconical envelope. The polarization fraction is ∼2.0% in this region. Some of these vectors seem to converge to IRAS 16547-E and IRAS 16547-W, the most massive protostars. Moreover, the velocity fields revealed from the spectral lines H13CO+(3−2) and HN13C(3−2) show velocity gradients with a good correspondence with the magnetic fields, which maybe are tracing the cavities of molecular outflows or maybe infalling in some parts. We derived a magnetic field strength in some filamentary regions that goes from 2 to 6.1 mG. We also find that the CS(5−4) molecular line emission reveals multiple outflow cavities or bow shocks with different orientations, some of which seem to follow the NW–SE radio thermal jet.
{"title":"Magnetic Fields in Massive Star-forming Regions (MagMaR). IV. Tracing the Magnetic Fields in the O-type Protostellar System IRAS 16547–4247","authors":"Luis A. Zapata, Manuel Fernández-López, Patricio Sanhueza, Josep M. Girart, Luis F. Rodríguez, Paulo Cortés, Patrick Koch, Maria T. Beltrán, Kate Pattle, Henrik Beuther, Piyali Saha, Wenyu Jiao, Fengwei Xu, Xing Walker Lu, Fernando Olguin, Shanghuo Li, Ian W. Stephens, Ji-hyun Kang, Yu Cheng, Spandan Choudhury, Kaho Morii, Eun Jung Chung, Jia-Wei Wang, Jihye Hwang, A-Ran Lyo, Q. Zhang and Huei-Ru Vivien Chen","doi":"10.3847/1538-4357/ad701d","DOIUrl":"https://doi.org/10.3847/1538-4357/ad701d","url":null,"abstract":"The formation of the massive stars, and in particular, the role that the magnetic fields play in their early evolutionary phase is still far from being completely understood. Here, we present the Atacama Large Millimeter/submillimeter Array 1.2 mm full polarized continuum and H13CO+(3−2), CS(5−4), and HN13C(3−2) line observations with a high angular resolution (∼0.″4 or 1100 au). In the 1.2 mm continuum emission, we reveal a dusty envelope surrounding the massive protostars, IRAS16547-E and IRAS16547-W, with dimensions of ∼10,000 au. This envelope has a biconical structure likely carved by the powerful thermal radio jet present in region. The magnetic field vectors follow very well the biconical envelope. The polarization fraction is ∼2.0% in this region. Some of these vectors seem to converge to IRAS 16547-E and IRAS 16547-W, the most massive protostars. Moreover, the velocity fields revealed from the spectral lines H13CO+(3−2) and HN13C(3−2) show velocity gradients with a good correspondence with the magnetic fields, which maybe are tracing the cavities of molecular outflows or maybe infalling in some parts. We derived a magnetic field strength in some filamentary regions that goes from 2 to 6.1 mG. We also find that the CS(5−4) molecular line emission reveals multiple outflow cavities or bow shocks with different orientations, some of which seem to follow the NW–SE radio thermal jet.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.3847/1538-4357/ad74fb
Tian-Yu Tu, 天宇 涂, Prathap Rayalacheruvu, Liton Majumdar, Yang Chen, 阳 陈, Ping Zhou, 平 周 and Miguel Santander-García
Cosmic rays (CRs) have strong influences on the chemistry of dense molecular clouds (MCs). To study the detailed chemistry induced by CRs, we conducted a Yebes W-band line survey towards an unshocked MC (which we named 3C391:NML) associated with supernova remnant 3C 391. We detected emission lines of 18 molecular species in total and estimated their column densities with local thermodynamic equilibrium (LTE) and non-LTE analysis. Using the abundance ratio N(HCO+)/N(CO) and an upper limit of N(DCO+)/N(HCO+), we estimated that the CR ionization rate of 3C391:NML is ζ ≳ 2.7 × 10−14 s−1 with an analytic method. However, we caution against adopting this value because chemical equilibrium, which is a prerequisite of using the equations, is not necessarily reached in 3C391:NML. We observed lower N(HCO+)/N(HOC+), higher N(HCS+)/N(CS), and higher X(l-C3H+) by an order of magnitude in 3C391:NML than the typical values in quiescent dense MCs. We found that an enhanced CR ionization rate (of order ∼10−15 or ∼10−14 s−1) is needed to reproduce the observation with a chemical model. This is higher than the values found in typical MCs by 2–3 orders of magnitude.
{"title":"A Yebes W-band Line Survey towards an Unshocked Molecular Cloud of Supernova Remnant 3C 391: Evidence of Cosmic-Ray-Induced Chemistry","authors":"Tian-Yu Tu, 天宇 涂, Prathap Rayalacheruvu, Liton Majumdar, Yang Chen, 阳 陈, Ping Zhou, 平 周 and Miguel Santander-García","doi":"10.3847/1538-4357/ad74fb","DOIUrl":"https://doi.org/10.3847/1538-4357/ad74fb","url":null,"abstract":"Cosmic rays (CRs) have strong influences on the chemistry of dense molecular clouds (MCs). To study the detailed chemistry induced by CRs, we conducted a Yebes W-band line survey towards an unshocked MC (which we named 3C391:NML) associated with supernova remnant 3C 391. We detected emission lines of 18 molecular species in total and estimated their column densities with local thermodynamic equilibrium (LTE) and non-LTE analysis. Using the abundance ratio N(HCO+)/N(CO) and an upper limit of N(DCO+)/N(HCO+), we estimated that the CR ionization rate of 3C391:NML is ζ ≳ 2.7 × 10−14 s−1 with an analytic method. However, we caution against adopting this value because chemical equilibrium, which is a prerequisite of using the equations, is not necessarily reached in 3C391:NML. We observed lower N(HCO+)/N(HOC+), higher N(HCS+)/N(CS), and higher X(l-C3H+) by an order of magnitude in 3C391:NML than the typical values in quiescent dense MCs. We found that an enhanced CR ionization rate (of order ∼10−15 or ∼10−14 s−1) is needed to reproduce the observation with a chemical model. This is higher than the values found in typical MCs by 2–3 orders of magnitude.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.3847/1538-4357/ad779b
M. C. Li and W. Li
Nitrogen lines are widely observed in astrophysical spectra and provide important diagnostics for plasma properties. In this work, we present extended calculations for accurate energy levels, electric dipole radiative transition parameters, and lifetimes for the lowest 102 states of the 2s22p2, 2s2p3, 2s2p23s, 2s22p{n1l, n2d, 4f}(n1 = 3–5, l = s, p, n2 = 3, 4), and 2p4 configurations of N ii within the framework of the fully relativistic multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods. These data are useful for modeling astrophysical spectra, for example, for nitrogen abundance determinations in early B-type stars, and for studying the compositions and plasma properties of H ii regions and planetary nebulae. Our computed transition parameters are compared with available experimental and theoretical data. The accuracy of the calculations is also assessed via a statistical analysis of the differences between the transition rates in the Babushkin and Coulomb gauges and by consideration of cancellation factors. In this way, 201 of the 1656 transitions computed in this work are estimated to be from accurate to better than 3%, corresponding to an accuracy class of A.
氮线在天体物理光谱中被广泛观测到，并为等离子体特性提供了重要的诊断依据。在这项工作中，我们在完全相对论多构型 Dirac-Hartree-Fock 和相对论构型相互作用方法的框架内，对 N ii 的 2s22p2、2s2p3、2s2p23s、2s22p{n1l, n2d, 4f}(n1 = 3-5, l = s, p, n2 = 3, 4) 和 2p4 构型的最低 102 态的精确能级、电偶极子辐射转变参数和寿命进行了扩展计算。这些数据有助于建立天体物理光谱模型，例如，用于确定早期 B 型恒星的氮丰度，以及研究 H ii 区域和行星状星云的成分和等离子体特性。我们将计算出的过渡参数与现有的实验和理论数据进行了比较。计算的准确性还通过对巴布什金量规和库仑量规中转变率之间差异的统计分析以及对抵消因素的考虑进行了评估。这样，在这项工作中计算出的 1656 个转变中，估计有 201 个转变的精确度在 3% 以上，相当于 A 级精确度。
{"title":"Atomic Data for Astrophysically Important Spectral Lines of Singly Ionized Nitrogen","authors":"M. C. Li and W. Li","doi":"10.3847/1538-4357/ad779b","DOIUrl":"https://doi.org/10.3847/1538-4357/ad779b","url":null,"abstract":"Nitrogen lines are widely observed in astrophysical spectra and provide important diagnostics for plasma properties. In this work, we present extended calculations for accurate energy levels, electric dipole radiative transition parameters, and lifetimes for the lowest 102 states of the 2s22p2, 2s2p3, 2s2p23s, 2s22p{n1l, n2d, 4f}(n1 = 3–5, l = s, p, n2 = 3, 4), and 2p4 configurations of N ii within the framework of the fully relativistic multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods. These data are useful for modeling astrophysical spectra, for example, for nitrogen abundance determinations in early B-type stars, and for studying the compositions and plasma properties of H ii regions and planetary nebulae. Our computed transition parameters are compared with available experimental and theoretical data. The accuracy of the calculations is also assessed via a statistical analysis of the differences between the transition rates in the Babushkin and Coulomb gauges and by consideration of cancellation factors. In this way, 201 of the 1656 transitions computed in this work are estimated to be from accurate to better than 3%, corresponding to an accuracy class of A.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.3847/1538-4357/ad71c5
Barnali Das, Poonam Chandra and Véronique Petit
Main-sequence radio pulse emitters (MRPs) are magnetic early-type stars that produce coherent radio emission observed in the form of periodic radio pulses. The emission mechanism behind this is the electron-cyclotron maser emission (ECME). Among all kinds of magnetospheric emission, ECME is unique due to its high directivity and intrinsically narrow bandwidth. The emission is also highly circularly polarized and the sign of polarization is opposite for the two magnetic hemispheres. This combination of properties makes ECME highly sensitive to the three-dimensional structures in the stellar magnetospheres. This is especially significant for late-B and A-type magnetic stars that do not emit other types of magnetospheric emission such as Hα, the key probe used to trace magnetospheric densities. In this paper, we use an ultra-wideband observation (0.4–2 GHz) of a late B-type MRP HD 133880 to demonstrate how we can extract information on plasma distribution from ECME. We achieve this by examining the differences in pulse arrival times (“lags”) as a function of frequencies and qualitatively comparing those with lags obtained by simulating ECME ray paths in hot stars’ magnetospheres. This reveals that the stellar magnetosphere has a disk-like overdensity inclined to the magnetic equator with a centrally concentrated density that primarily affects the intermediate frequencies (400–800 MHz). This result, which is consistent with the recent density model proposed for hotter centrifugally supported magnetospheres, lends support to the idea of a unifying model for magnetospheric operations in early-type stars, and also provides further motivation to fully characterize the ECME phenomenon in large-scale stellar magnetospheres.
{"title":"Coherent Radio Emission from “Main-sequence Radio Pulse Emitters”: A New Stellar Diagnostic to Probe 3D Magnetospheric Structures","authors":"Barnali Das, Poonam Chandra and Véronique Petit","doi":"10.3847/1538-4357/ad71c5","DOIUrl":"https://doi.org/10.3847/1538-4357/ad71c5","url":null,"abstract":"Main-sequence radio pulse emitters (MRPs) are magnetic early-type stars that produce coherent radio emission observed in the form of periodic radio pulses. The emission mechanism behind this is the electron-cyclotron maser emission (ECME). Among all kinds of magnetospheric emission, ECME is unique due to its high directivity and intrinsically narrow bandwidth. The emission is also highly circularly polarized and the sign of polarization is opposite for the two magnetic hemispheres. This combination of properties makes ECME highly sensitive to the three-dimensional structures in the stellar magnetospheres. This is especially significant for late-B and A-type magnetic stars that do not emit other types of magnetospheric emission such as Hα, the key probe used to trace magnetospheric densities. In this paper, we use an ultra-wideband observation (0.4–2 GHz) of a late B-type MRP HD 133880 to demonstrate how we can extract information on plasma distribution from ECME. We achieve this by examining the differences in pulse arrival times (“lags”) as a function of frequencies and qualitatively comparing those with lags obtained by simulating ECME ray paths in hot stars’ magnetospheres. This reveals that the stellar magnetosphere has a disk-like overdensity inclined to the magnetic equator with a centrally concentrated density that primarily affects the intermediate frequencies (400–800 MHz). This result, which is consistent with the recent density model proposed for hotter centrifugally supported magnetospheres, lends support to the idea of a unifying model for magnetospheric operations in early-type stars, and also provides further motivation to fully characterize the ECME phenomenon in large-scale stellar magnetospheres.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.3847/1538-4357/ad7019
Jihye Hwang, Chang Won Lee, Jongsoo Kim, Eun Jung Chung and Kee-Tae Kim
Measuring the strength of a three-dimensional (3D) magnetic field vector is challenging as it is not easy to recognize whether its line-of-sight (LOS) and plane-of-sky (POS) components are obtained from the same region. CN (N = 1–0) emission has been used to get the LOS component of a magnetic field (BLOS) from its Zeeman splitting lines, while dust continuum emission has been used to get the POS component of a magnetic field (BPOS). We use the CN (N = 1–0) data observed with the Taeduk Radio Astronomy Observatory 14 m telescope and the dust continuum data from the Herschel archive toward six high-mass star-forming regions in order to test whether CN line and dust continuum emission can trace a similar region and thus can be used for inferring 3D magnetic field strength. Our comparison between CN and H2 column densities for all targets indicates that CN line emission tends to be strong toward bright continuum regions. The positions of peak CN column densities are particularly well correlated with those of peak H2 column densities, at least over the H2 column density of 8.0 × 1022 cm−2 within one or two telescope beam sizes in all targets, implying that CN-line- and dust-continuum-emitting regions are likely spatially coincident. This enabled us to make the reliable measurement of the 3D magnetic field strengths of five targets by taking a vector sum of their BLOS and BPOS, helping to decide the magnetical criticality of the targets as supercritical or transcritical.
{"title":"The Spatial Correlation between CN-line- and Dust-continuum-emitting Regions in High-mass Star-forming Clouds","authors":"Jihye Hwang, Chang Won Lee, Jongsoo Kim, Eun Jung Chung and Kee-Tae Kim","doi":"10.3847/1538-4357/ad7019","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7019","url":null,"abstract":"Measuring the strength of a three-dimensional (3D) magnetic field vector is challenging as it is not easy to recognize whether its line-of-sight (LOS) and plane-of-sky (POS) components are obtained from the same region. CN (N = 1–0) emission has been used to get the LOS component of a magnetic field (BLOS) from its Zeeman splitting lines, while dust continuum emission has been used to get the POS component of a magnetic field (BPOS). We use the CN (N = 1–0) data observed with the Taeduk Radio Astronomy Observatory 14 m telescope and the dust continuum data from the Herschel archive toward six high-mass star-forming regions in order to test whether CN line and dust continuum emission can trace a similar region and thus can be used for inferring 3D magnetic field strength. Our comparison between CN and H2 column densities for all targets indicates that CN line emission tends to be strong toward bright continuum regions. The positions of peak CN column densities are particularly well correlated with those of peak H2 column densities, at least over the H2 column density of 8.0 × 1022 cm−2 within one or two telescope beam sizes in all targets, implying that CN-line- and dust-continuum-emitting regions are likely spatially coincident. This enabled us to make the reliable measurement of the 3D magnetic field strengths of five targets by taking a vector sum of their BLOS and BPOS, helping to decide the magnetical criticality of the targets as supercritical or transcritical.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.3847/1538-4357/ad6f9b
Xiaowei Ou, 筱葳 欧, Alexander P. Ji, Anna Frebel, Rohan P. Naidu and Guilherme Limberg
Neutron star mergers (NSMs) produce r-process elements after a time-delayed inspiral process. Once a significant number of NSMs are present in a galaxy, r-process elements, such as Eu, are expected to significantly increase with time. Yet, there have been limited observational data in support of Eu increasing within Local Group galaxies. We have obtained high-resolution Magellan/MIKE observations of 43 metal-poor stars in the Gaia-Sausage/Enceladus (GSE) tidally disrupted galaxy with −2.5 < [Fe/H] < −1. For the first time, we find a clear rise in [Eu/Mg] with increasing [Mg/H] within one galaxy. We use a simple chemical evolution model to study how such a rise can result from the interplay of prompt and delayed r-process enrichment events. Delayed r-process sources are required to explain the rise and subsequent leveling off of [Eu/Mg] in this disrupted galaxy. However, the rise may be explained by delayed r-process sources with either short (∼10 Myr) or long (∼500 Myr) minimum delay times. Future studies on the nature of r-process sources and their enrichment processes in the GSE will require additional stars in the GSE at even lower metallicities than the present study.
{"title":"The Rise of the r-process in the Gaia-Sausage/Enceladus Dwarf Galaxy ∗","authors":"Xiaowei Ou, 筱葳 欧, Alexander P. Ji, Anna Frebel, Rohan P. Naidu and Guilherme Limberg","doi":"10.3847/1538-4357/ad6f9b","DOIUrl":"https://doi.org/10.3847/1538-4357/ad6f9b","url":null,"abstract":"Neutron star mergers (NSMs) produce r-process elements after a time-delayed inspiral process. Once a significant number of NSMs are present in a galaxy, r-process elements, such as Eu, are expected to significantly increase with time. Yet, there have been limited observational data in support of Eu increasing within Local Group galaxies. We have obtained high-resolution Magellan/MIKE observations of 43 metal-poor stars in the Gaia-Sausage/Enceladus (GSE) tidally disrupted galaxy with −2.5 < [Fe/H] < −1. For the first time, we find a clear rise in [Eu/Mg] with increasing [Mg/H] within one galaxy. We use a simple chemical evolution model to study how such a rise can result from the interplay of prompt and delayed r-process enrichment events. Delayed r-process sources are required to explain the rise and subsequent leveling off of [Eu/Mg] in this disrupted galaxy. However, the rise may be explained by delayed r-process sources with either short (∼10 Myr) or long (∼500 Myr) minimum delay times. Future studies on the nature of r-process sources and their enrichment processes in the GSE will require additional stars in the GSE at even lower metallicities than the present study.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.3847/1538-4357/ad64d3
Akash Anumarlapudi, Dougal Dobie, David L. Kaplan, Tara Murphy, Assaf Horesh, Emil Lenc, Laura Driessen, Stefan W. Duchesne, Hannah Dykaar, B. M. Gaensler, Timothy J. Galvin, Joe Grundy, George Heald, Aidan W. Hotan, Minh Huynh, James K. Leung, David McConnell, Vanessa A. Moss, Joshua Pritchard, Wasim Raja, Kovi Rose, Gregory Sivakoff, Yuanming Wang, Ziteng Wang, Mark H. Wieringa and Matthew T. Whiting
Late-time (∼a year) radio follow-up of optically discovered tidal disruption events (TDEs) is increasingly resulting in detections at radio wavelengths, and there is growing evidence for this late-time radio activity to be common to the broad class of subrelativistic TDEs. Detailed studies of some of these TDEs at radio wavelengths are also challenging the existing models for radio emission. Using all-sky multiepoch data from the Australian Square Kilometre Array Pathfinder (ASKAP), taken as a part of the Rapid ASKAP Continuum Survey (RACS), we searched for radio counterparts to a sample of optically discovered TDEs. We detected late-time emission at RACS frequencies (742–1032 MHz) in five TDEs, reporting the independent discovery of radio emission from TDE AT 2019ahk and extending the time baseline out to almost 3000 days for some events. Overall, we find that at least of the population of optically discovered TDEs has detectable radio emission in the RACS survey, while also noting that the true fraction can be higher given the limited cadence (two epochs separated by ∼3 yr) of the survey. Finally, we project that the ongoing higher-cadence (∼2 months) ASKAP Variable and Slow Transients survey can detect ∼20 TDEs in its operational span (4 yr), given the current rate from optical surveys.
{"title":"Radio Afterglows from Tidal Disruption Events: An Unbiased Sample from ASKAP RACS","authors":"Akash Anumarlapudi, Dougal Dobie, David L. Kaplan, Tara Murphy, Assaf Horesh, Emil Lenc, Laura Driessen, Stefan W. Duchesne, Hannah Dykaar, B. M. Gaensler, Timothy J. Galvin, Joe Grundy, George Heald, Aidan W. Hotan, Minh Huynh, James K. Leung, David McConnell, Vanessa A. Moss, Joshua Pritchard, Wasim Raja, Kovi Rose, Gregory Sivakoff, Yuanming Wang, Ziteng Wang, Mark H. Wieringa and Matthew T. Whiting","doi":"10.3847/1538-4357/ad64d3","DOIUrl":"https://doi.org/10.3847/1538-4357/ad64d3","url":null,"abstract":"Late-time (∼a year) radio follow-up of optically discovered tidal disruption events (TDEs) is increasingly resulting in detections at radio wavelengths, and there is growing evidence for this late-time radio activity to be common to the broad class of subrelativistic TDEs. Detailed studies of some of these TDEs at radio wavelengths are also challenging the existing models for radio emission. Using all-sky multiepoch data from the Australian Square Kilometre Array Pathfinder (ASKAP), taken as a part of the Rapid ASKAP Continuum Survey (RACS), we searched for radio counterparts to a sample of optically discovered TDEs. We detected late-time emission at RACS frequencies (742–1032 MHz) in five TDEs, reporting the independent discovery of radio emission from TDE AT 2019ahk and extending the time baseline out to almost 3000 days for some events. Overall, we find that at least of the population of optically discovered TDEs has detectable radio emission in the RACS survey, while also noting that the true fraction can be higher given the limited cadence (two epochs separated by ∼3 yr) of the survey. Finally, we project that the ongoing higher-cadence (∼2 months) ASKAP Variable and Slow Transients survey can detect ∼20 TDEs in its operational span (4 yr), given the current rate from optical surveys.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.3847/1538-4357/ad7377
Nushkia Chamba, Pamela M. Marcum, Amélie Saintonge, Alejandro S. Borlaff, Matthew J. Hayes, Valentin J. M. Le Gouellec, S. Drew Chojnowski and Michael N. Fanelli
Mapping stars and gas in nearby galaxies is fundamental for understanding their growth and the impact of their environment. This issue is addressed by comparing the stellar “edges” of galaxies Dstellar, defined as the outermost diameter where in situ star formation significantly drops, with the gaseous distribution parameterized by the neutral atomic hydrogen diameter measured at 1 M⊙ pc−2, DHI. By sampling a broad H i mass range 105M⊙ < MHI < 1011M⊙, we find several dwarf galaxies with MHI < 109M⊙ from the field and Fornax Cluster that are distinguished by Dstellar ≫ DHI. For the cluster dwarfs, the average H i surface density near Dstellar is ∼0.3 M⊙ pc−2, reflecting the impact of quenching and outside-in gas removal from ram pressure and tidal interactions. In comparison, Dstellar/DHI ranges between 0.5 and 2 in dwarf field galaxies, consistent with the expectations from stellar feedback. Only more massive disk galaxies in the field can thus be characterized by the common assumption that Dstellar ≲ DHI. We discover a break in the Dstellar–M⋆ relation at mbreak ∼ 4 × 108M⊙ that potentially differentiates the low-mass regime, where the influence of stellar feedback and environmental processes more prominently regulates the sizes of nearby galaxies. Our results highlight the importance of combining deep optical and H i imaging for understanding galaxy evolution.
{"title":"A Break in the Size–Stellar Mass Relation: Evidence for Quenching and Feedback in Dwarf Galaxies","authors":"Nushkia Chamba, Pamela M. Marcum, Amélie Saintonge, Alejandro S. Borlaff, Matthew J. Hayes, Valentin J. M. Le Gouellec, S. Drew Chojnowski and Michael N. Fanelli","doi":"10.3847/1538-4357/ad7377","DOIUrl":"https://doi.org/10.3847/1538-4357/ad7377","url":null,"abstract":"Mapping stars and gas in nearby galaxies is fundamental for understanding their growth and the impact of their environment. This issue is addressed by comparing the stellar “edges” of galaxies Dstellar, defined as the outermost diameter where in situ star formation significantly drops, with the gaseous distribution parameterized by the neutral atomic hydrogen diameter measured at 1 M⊙ pc−2, DHI. By sampling a broad H i mass range 105M⊙ < MHI < 1011M⊙, we find several dwarf galaxies with MHI < 109M⊙ from the field and Fornax Cluster that are distinguished by Dstellar ≫ DHI. For the cluster dwarfs, the average H i surface density near Dstellar is ∼0.3 M⊙ pc−2, reflecting the impact of quenching and outside-in gas removal from ram pressure and tidal interactions. In comparison, Dstellar/DHI ranges between 0.5 and 2 in dwarf field galaxies, consistent with the expectations from stellar feedback. Only more massive disk galaxies in the field can thus be characterized by the common assumption that Dstellar ≲ DHI. We discover a break in the Dstellar–M⋆ relation at mbreak ∼ 4 × 108M⊙ that potentially differentiates the low-mass regime, where the influence of stellar feedback and environmental processes more prominently regulates the sizes of nearby galaxies. Our results highlight the importance of combining deep optical and H i imaging for understanding galaxy evolution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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