Astrophysical Journal最新文献

{"title":"Broadband Radio Study of the North Polar Spur: Origin of the Spectral Turnover with Insights into the X-Ray and Gamma-Ray Spectra","authors":"Ryoji Iwashita, Jun Kataoka, Yoshiaki Sofue","doi":"10.3847/1538-4357/ad0374","DOIUrl":"https://doi.org/10.3847/1538-4357/ad0374","url":null,"abstract":"Abstract The North Polar Spur (NPS) is a giant structure that is clearly visible in both radio and X-ray all-sky maps. We analyzed broadband radio observations covering a range between 22 MHz and 70 GHz to systematically analyze the thermal/nonthermal emissions associated with the NPS. We demonstrate that the radio emission of the NPS comprises synchrotron, free–free, and dust emission; however, synchrotron emissions dominate over other emissions, especially at high Galactic latitudes. Moreover, the synchrotron spectra exhibit a power-law behavior with N ( γ ) ∝ γ − s ( s ≃ 1.8–2.4) up to a few GHz moderated by a turnover at ν brk ≃ 1 GHz, above which the spectral index s decreases by one. Assuming that the turnover is due to the electrons being cooled by synchrotron radiation before escaping (or advecting) from the emission region, the magnetic field strength can be estimated to be B ∼ 8 μ G if the NPS is a distant structure that is near the Galactic center (GC). However, an unreasonably strong B ∼ 114 μ G is required if the NPS is near the local supernova remnant (SNR). The corresponding nonthermal energy stored in the NPS is E n/th ≃ 4.4 × 10 55 erg in the GC scenario, whereas E n/th ≃ 4.1 × 10 52 erg is difficult to explain with a single local SNR. We also estimated the gamma-ray emission associated with the NPS through inverse Comptonization of the cosmic microwave background, which peaks at 100–1000 keV with a flux of ν F ν ∼ 10 −9 erg cm −2 s −1 sr −1 in the GC model, and may be a good candidate for detection by future X-ray/gamma-ray observatories.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135765726","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}

{"title":"Reconstruction of a Scale-dependent Gravitational Phase Transition","authors":"Marzieh Farhang, Nima Khosravi","doi":"10.3847/1538-4357/acfa6e","DOIUrl":"https://doi.org/10.3847/1538-4357/acfa6e","url":null,"abstract":"Abstract In this work we extend our earlier phenomenological model for a gravitational phase transition and its generalization to early times by letting the modifications in the linearly perturbed Einstein equations be scale dependent. These modifications are characterized as deviations of the parameters μ ( z , k ) and γ ( z , k ) from their values in general relativity (GR). The scale-dependent amplitudes of modified μ ( z , k ) and γ ( z , k ) and the parameters defining the phase transition, along with the standard cosmological parameters, are measured by various data combinations. Out of the perturbation parameters, we construct gravity eigenmodes that represent patterns of perturbations best detectable by data. We detect no significant deviation from GR in these parameters. However, the larger parameter space produced due to the new degrees of freedom allows for the reconciliation of various data sets that are in tension in ΛCDM. In particular, we find H 0 = 71.9 ± 9.2 from anisotropies of the cosmic microwave background as measured by Planck (and various measurements of the baryonic acoustic oscillations, in agreement with local Hubble measurements). We also find that the σ 8 tension between the measurements of the Dark Energy Survey and Planck is reduced to less than 1 σ .","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510573","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}

{"title":"Are Switchback Boundaries Observed by Parker Solar Probe Closed?","authors":"Nina Bizien, Thierry Dudok de Wit, Clara Froment, Marco Velli, Anthony W. Case, Stuart D. Bale, Justin Kasper, Phyllis Whittlesey, Robert MacDowall, Davin Larson","doi":"10.3847/1538-4357/acf99a","DOIUrl":"https://doi.org/10.3847/1538-4357/acf99a","url":null,"abstract":"Abstract Switchbacks are sudden and large deflections in the magnetic field that Parker Solar Probe frequently observes in the inner heliosphere. Their ubiquitous occurrence has prompted numerous studies to determine their nature and origin. Our goal is to describe the boundary of these switchbacks using a series of events detected during the spacecraft’s first encounter with the Sun. Using FIELDS and SWEAP data, we investigate different methods for determining the boundary normal. The observed boundaries are arc-polarized structures with a rotation that is always contained in a plane. Classical minimum variance analysis gives misleading results and overestimates the number of rotational discontinuities. We propose a robust geometric method to identify the nature of these discontinuities, which involves determining whether or not the plane that contains them also includes the origin ( B = 0). Most boundaries appear to have the same characteristics as tangential discontinuities in the context of switchbacks, with little evidence for having rotational discontinuities. We find no effect of the size of the Parker spiral deviation. Furthermore, the thickness of the boundary is within MHD scales. We conclude that most of the switchback boundaries observed by Parker Solar Probe are likely to be closed, in contrast to previous studies. Our results suggest that their erosion may be much slower than expected.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135516409","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}

{"title":"Reconstructing Lyα Fields from Low-resolution Hydrodynamical Simulations with Deep Learning","authors":"Cooper Jacobus, Peter Harrington, Zarija Lukić","doi":"10.3847/1538-4357/acfcb5","DOIUrl":"https://doi.org/10.3847/1538-4357/acfcb5","url":null,"abstract":"Abstract Hydrodynamical cosmological simulations are a powerful tool for accurately predicting the properties of the intergalactic medium (IGM) and for producing mock skies that can be compared against observational data. However, the need to resolve density fluctuation in the IGM puts a stringent requirement on the resolution of such simulations, which in turn limits the volumes that can be modeled, even on the most powerful supercomputers. In this work, we present a novel modeling method that combines physics-driven simulations with data-driven generative neural networks to produce outputs that are qualitatively and statistically close to the outputs of hydrodynamical simulations employing eight times higher resolution. We show that the Ly α flux field, as well as the underlying hydrodynamic fields, have greatly improved statistical fidelity over a low-resolution simulation. Importantly, the design of our neural network allows for sampling multiple realizations from a given input, enabling us to quantify the model uncertainty. Using test data, we demonstrate that this model uncertainty correlates well with the true error of the Ly α flux prediction. Ultimately, our approach allows for training on small simulation volumes and applying it to much larger ones, opening the door to producing accurate Ly α mock skies in volumes of Hubble size, as will be probed with DESI and future spectroscopic sky surveys.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135564541","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}

{"title":"Solar Magnetic Polarity Effect on Neutron Monitor Count Rates: Comparing Latitude Surveys and Antarctic Stations","authors":"K. Poopakun, W. Nuntiyakul, S. Khamphakdee, A. Seripienlert, D. Ruffolo, P. Evenson, P. Jiang, P. Chuanraksasat, K. Munakata, M. L. Duldig, J. E. Humble, J. Madsen, B. Soonthornthum, S. Komonjinda","doi":"10.3847/1538-4357/ad02f1","DOIUrl":"https://doi.org/10.3847/1538-4357/ad02f1","url":null,"abstract":"Abstract The Galactic cosmic-ray spectrum manifests pronounced variations over the 11 yr sunspot cycle and more subtle variations over the 22 yr solar magnetic cycle. An important tool to study these variations is repeated latitude surveys with neutron monitors (NMs) on board icebreakers in conjunction with land-based references. We revisit 13 annual latitude surveys from 1994 to 2007 using reference data from the Mawson NM instead of McMurdo NM (which closed in 2017). We then consider two more latitude surveys (2018 and 2019) with a monitor similar to the 3NM64 in the previous surveys but without lead rings around the central tube, a so-called “semi-leaded neutron monitor.” The new surveys extend the linear relationship among data taken at different cutoff rigidity ranges. They also confirm the “crossover” measured near solar minima during epochs of opposite solar magnetic polarity and the absence of a crossover for epochs having the same solar magnetic polarity.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714757","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}

{"title":"NICER Observations of Thermonuclear Bursts from 4U 1728-34: Detection of Oscillations prior to the Onset of Two Bursts","authors":"Z. Funda Bostancı, Tuğba Boztepe, Tolga Güver, Tod E. Strohmayer, Yuri Cavecchi, Ersin Göğüş, Diego Altamirano, Peter Bult, Deepto Chakrabarty, Sebastien Guillot, Gaurava K. Jaisawal, Christian Malacaria, Giulio C. Mancuso, Andrea Sanna, Jean H. Swank","doi":"10.3847/1538-4357/acfc4c","DOIUrl":"https://doi.org/10.3847/1538-4357/acfc4c","url":null,"abstract":"Abstract We present temporal and time-resolved spectral analyses of all the thermonuclear X-ray bursts observed from the neutron star low-mass X-ray binary 4U 1728−34 with NICER from 2017 June to 2019 September. In total, we detected 11 X-ray bursts from the source and performed time-resolved spectroscopy. Unlike some of the earlier results for other bursting sources from NICER, our spectral results indicate that the use of a scaling factor for the persistent emission is not statistically necessary. This is primarily a result of the strong interstellar absorption in the line of sight toward 4U 1728−34, which causes the count rates to be significantly lower at low energies. We also searched for burst oscillations and detected modulations in six different bursts at around the previously known burst oscillation frequency of 363 Hz. Finally, we report the detection of oscillations prior to two bursts at 356 and 359 Hz, respectively. This is the first time in the literature where burst oscillations are detected before the rapid rise in X-ray flux, from any known burster. These oscillations disappear as soon as the burst starts to rise and occur at a somewhat lower frequency than the oscillations we detect during the bursts.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714981","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}

{"title":"Nitrogen-enriched, Highly Pressurized Nebular Clouds Surrounding a Super Star Cluster at Cosmic Noon","authors":"Massimo Pascale, Liang Dai, Christopher F. McKee, Benny T.-H. Tsang","doi":"10.3847/1538-4357/acf75c","DOIUrl":"https://doi.org/10.3847/1538-4357/acf75c","url":null,"abstract":"Abstract Strong lensing offers a precious opportunity for studying the formation and early evolution of super star clusters that are rare in our cosmic backyard. The Sunburst Arc, a lensed Cosmic Noon galaxy, hosts a young super star cluster with escaping Lyman continuum radiation. Analyzing archival Hubble Space Telescope images and emission line data from Very Large Telescope/MUSE and X-shooter, we construct a physical model for the cluster and its surrounding photoionized nebula. We confirm that the cluster is ≲4 Myr old, is extremely massive M ⋆ ∼ 10 7 M ⊙ , and yet has a central component as compact as several parsecs, and we find a gas-phase metallicity Z = (0.22 ± 0.03) Z ⊙ . The cluster is surrounded by ≳10 5 M ⊙ of dense clouds that have been pressurized to P ∼ 10 9 K cm −3 by perhaps stellar radiation at within 10 pc. These should have large neutral columns N HI &gt; 10 22.8 cm −2 to survive rapid ejection by radiation pressure. The clouds are likely dusty as they show gas-phase depletion of silicon, and may be conducive to secondary star formation if N HI &gt; 10 24 cm −2 or if they sink farther toward the cluster center. Detecting strong [N iii ] λ λ 1750,1752, we infer heavy nitrogen enrichment <?CDATA $mathrm{log}({rm{N}}/{rm{O}})=-{0.21}_{-0.11}^{+0.10}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>log</mml:mi> <mml:mo stretchy=\"false\">(</mml:mo> <mml:mi mathvariant=\"normal\">N</mml:mi> <mml:mrow> <mml:mo stretchy=\"true\">/</mml:mo> </mml:mrow> <mml:mi mathvariant=\"normal\">O</mml:mi> <mml:mo stretchy=\"false\">)</mml:mo> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.21</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . This requires efficiently retaining ≳500 M ⊙ of nitrogen in the high-pressure clouds from massive stars heavier than 60 M ⊙ up to 4 Myr. We suggest a physical origin of the high-pressure clouds from partial or complete condensation of slow massive star ejecta, which may have an important implication for the puzzle of multiple stellar populations in globular clusters.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372183","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}

{"title":"New and Improved Lyα Reconstructions for M and K Dwarfs","authors":"Angeli Sandoval, Allison Youngblood, R. O. Parke Loyd, Kevin France","doi":"10.3847/1538-4357/acf6c0","DOIUrl":"https://doi.org/10.3847/1538-4357/acf6c0","url":null,"abstract":"The Lyα emission line is the brightest UV emission line in M and K dwarf spectra and serves as an important tool for studies of stellar chromospheres, the interstellar medium, and exoplanet atmospheres. However, Lyα observations have proven difficult due to the strong absorption by the interstellar medium, necessitating a reconstruction of the intrinsic stellar line from the observed spectrum. We have performed new Lyα reconstructions on the MUSCLES Treasury Survey stars, incorporating improved parameterizations for the intrinsic line wings and line core. We present an analysis of how the updated Lyα fluxes could impact photochemical and atmospheric escape studies and flux–flux scaling relations with other chromospheric emission lines such as Ca ii H and K. We find the overall intrinsic Lyα flux of our star sample decreases by as little as 10% to as much as ∼5× fainter compared to previous findings. The exception to this flux decrease is the M dwarf GJ 581, whose Lyα flux increased by 4%. These results will likely have a limited impact on the aforementioned studies that rely on Lyα fluxes.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372419","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}

{"title":"Radial and Local Density Dependence of Star Formation Properties in Galaxy Clusters from the Hyper Suprime-Cam Survey","authors":"Hung-Yu Jian, Lihwai Lin, Bau-Ching Hsieh, Keiichi Umetsu, Carlos Lopez-Coba, Masamune Oguri, Connor Bottrell, Yoshiki Toba, Yusei Koyama, Yu-Yen Chang, Tadayuki Kodama, Yutaka Komiyama, Surhud More, Kai-Yang Lin, Atsushi J. Nishizawa, Ichi Tanaka","doi":"10.3847/1538-4357/acfc22","DOIUrl":"https://doi.org/10.3847/1538-4357/acfc22","url":null,"abstract":"Abstract This study examines the impact of cluster environments on galaxy properties using data from the Hyper Suprime-Cam Subaru Strategic Program and an optically selected CAMIRA cluster sample. Specifically, the study analyzes the fractions of quiescent and green valley galaxies with stellar masses above 10 8.6 M ⊙ at z ∼ 0.2 and 10 9.8 M ⊙ at z ∼ 1.1, investigating their trends in radius and density. The results indicate that a slow quenching mechanism is at work, as evidenced by a radially independent specific star formation rate reduction of 0.1 dex for star-forming galaxies in a cluster environment. The study also finds that slow quenching dominates fast quenching only for low-mass galaxies (<10 9.2 M ⊙ ) near the cluster edge, based on their contributions to the quiescent fraction. After controlling for M * , z , and local overdensity, the study still finds a significant radial gradient in the quiescent fraction, indicating active ram pressure stripping in dense environments. That said, analyzing the density trend of the quiescent fraction with other fixed parameters suggests that radial and density-related quenching processes are equally crucial for low-mass cluster galaxies. The study concludes that ram pressure stripping is the primary environmental quenching mechanism for high stellar mass galaxies in clusters. By contrast, ram pressure stripping and density-related quenching processes act comparably for low-mass cluster galaxies around the center. Near the cluster boundary, starvation and harassment become the leading quenching processes for low stellar mass galaxies.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372613","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}

{"title":"TRAO Survey of Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). III. Filaments and Dense Cores in the NGC 2068 and NGC 2071 Regions of Orion B","authors":"Hyunju Yoo, Chang Won Lee, Eun Jung Chung, Shinyoung Kim, Mario Tafalla, Paola Caselli, Philip C. Myers, Kyoung Hee Kim, Tie Liu, Woojin Kwon, Archana Soam, Jongsoo Kim","doi":"10.3847/1538-4357/acf8c2","DOIUrl":"https://doi.org/10.3847/1538-4357/acf8c2","url":null,"abstract":"Abstract We present the results of molecular line observations performed toward the NGC 2068 and NGC 2071 regions of the Orion B cloud as the TRAO-FUNS project to study the roles of the filamentary structure in the formation of dense cores and stars in the clouds. Gaussian decomposition for the C 18 O spectra with multiple velocity components and the application of a friends-of-friends algorithm for the decomposed components allowed us to identify a few tens of velocity-coherent filaments. We also identified 48 dense cores from the observations of N 2 H + using a core finding tool, FellWalker. We performed a virial analysis for these filaments and dense cores, finding that the filaments with N 2 H + dense core are thermally supercritical, and the filaments with a larger ratio between the line mass and the thermal critical line mass tend to have more dense cores. We investigated the contribution of the nonthermal motions in dense cores and filaments, showing the dense cores are mostly in transonic/subsonic motions while their natal filaments are mostly in supersonic motions. This may indicate that gas turbulent motions in the filaments have been dissipated at the core scale to form the dense cores there. The filaments with (dynamically evolved) dense cores in infalling motions or with NH 2 D bright (or chemically evolved) dense cores are all found to be gravitationally critical. Therefore, the criticality of the filament is thought to provide a key condition for its fragmentation, the formation of dense cores, and their kinematical and chemical evolution.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135410326","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}