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The Astrophysical Journal (ApJ)

Resumen/Descripción – provisto por la editorial en inglés
The Astrophysical Journal is an open access journal devoted to recent developments, discoveries, and theories in astronomy and astrophysics. Publications in ApJ constitute significant new research that is directly relevant to astrophysical applications, whether based on observational results or on theoretical insights or modeling.
Palabras clave – provistas por la editorial

astronomy; astrophysics

Disponibilidad
Institución detectada Período Navegá Descargá Solicitá
No detectada desde jul. 1995 / hasta dic. 2023 IOPScience

Información

Tipo de recurso:

revistas

ISSN impreso

0004-637X

ISSN electrónico

1538-4357

Editor responsable

American Astronomical Society (AAS)

Idiomas de la publicación

  • inglés

País de edición

Reino Unido

Información sobre licencias CC

Creative Commons Atribución No comercial No obras derivadas Compartir igual

https://creativecommons.org/licenses/by/4.0/

Cobertura temática

Tabla de contenidos

Parallel Electron Heating through Landau Resonance with Lower Hybrid Waves at the Edge of Reconnection Ion Jets

Yong Ren; Lei DaiORCID; Chi Wang; Benoit LavraudORCID

<jats:title>Abstract</jats:title> <jats:p>We investigate lower hybrid waves in magnetic reconnection at the flank magnetopause using Magnetospheric Multiscale data. Intense emissions of lower hybrid waves are observed at the density boundary of the reconnection ion jet. Associated with the lower hybrid waves, electrons exhibit signatures of heating in the direction parallel to the magnetic field. Near the Landau resonance energy, the electron fluxes parallel to the magnetic field show oscillations at the same frequency as the lower hybrid waves. The electron flux oscillations are in phase or antiphase with the wave parallel electric field. These observations provide direct evidence for Landau resonance. Our analysis indicates that the density gradient at the edge of the ion jets provides free energy for the lower hybrid waves that further contribute to electron heating through Landau damping. These results shed light on the role of wave−particle interactions in the energy conversion chain of reconnection ion jets.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 5

Effects of Small-scale Absorption Systems on Neutral Islands during the Late Epoch of Reionization

Peng-Ju WuORCID; Yidong XuORCID; Xin ZhangORCID; Xuelei ChenORCID

<jats:title>Abstract</jats:title> <jats:p>The reionization process is expected to be prolonged by the small-scale absorbers (SSAs) of ionizing photons, which have been seen as Lyman-limit systems in quasar absorption line observations. We use a set of semi-numerical simulations to investigate the effects of absorption systems on the reionization process, especially their impacts on the neutral islands during the late epoch of reionization (EoR). Three models are studied, i.e., the extreme case of no-SSA model with a high level of ionizing background, the moderate-SSA model with a relatively high level of ionizing background, and the dense-SSA model with a low level of ionizing background. We find that while the characteristic scale of neutral regions decreases during the early and middle stages of reionization, it stays nearly unchanged at about 10 co-moving Mpc during the late stage for the no-SSA and moderate-SSA models. However, in the case of weak ionizing background in the dense-SSA model, the characteristic island scale shows obvious evolution, as large islands break into many small ones that are slowly ionized. The evolutionary behavior of neutral islands during the late EoR thus provides us with a novel way to constrain the abundance of SSAs. We discuss the 21 cm observation with the upcoming Square Kilometre Array. The different models can be distinguished by either the 21 cm imaging or the 21 cm power spectrum measurements.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 5

Machine Learning Classification to Identify Catastrophic Outlier Photometric Redshift Estimates

J. SingalORCID; G. Silverman; E. JonesORCID; T. Do; B. Boscoe; Y. Wan

<jats:title>Abstract</jats:title> <jats:p>We present results of using a basic binary classification neural network model to identify likely catastrophic outlier photometric redshift estimates of individual galaxies, based only on the galaxies’ measured photometric band magnitude values. We find that a simple implementation of this classification can identify a significant fraction of galaxies with catastrophic outlier photometric redshift estimates while falsely categorizing only a much smaller fraction of non-outliers. These methods have the potential to reduce the errors introduced into science analyses by catastrophic outlier photometric redshift estimates.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 6

Measuring Spin from Relative Photon-ring Sizes

Avery E. BroderickORCID; Paul TiedeORCID; Dominic W. PesceORCID; Roman GoldORCID

<jats:title>Abstract</jats:title> <jats:p>The direct detection of a bright, ring-like structure in horizon-resolving images of M87* by the Event Horizon Telescope (EHT) is a striking validation of general relativity. The angular size and shape of the ring is a degenerate measure of the location of the emission region, mass, and spin of the black hole. However, we show that the observation of multiple rings, corresponding to the low-order photon rings, can break this degeneracy and produce mass and spin measurements independent of the shape of the rings. We describe two potential experiments that would measure the spin. In the first, observations of the direct emission and <jats:italic>n</jats:italic> = 1 photon ring are made at multiple epochs with different emission locations. This method is conceptually similar to spacetime constraints that arise from variable structures (or hot spots) in that it breaks the near-perfect degeneracy between emission location, mass, and spin for polar observers using temporal variability. In the second, observations of the direct emission and <jats:italic>n</jats:italic> = 1 and <jats:italic>n</jats:italic> = 2 photon rings are made during a single epoch. For both schemes, additional observations comprise a test of general relativity. Thus, comparisons of EHT observations in 2017 and 2018 may be capable of producing the first horizon-scale spin estimates of M87* inferred from strong lensing alone. Additional observation campaigns from future high-frequency, Earth-sized, and space-based radio interferometers can produce high-precision tests of general relativity.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 6

Density Profile of the Ambient Circumnuclear Medium in Seyfert 1 Galaxies

Yijun WangORCID; Zhicheng HeORCID; Junjie Mao; Jelle Kaastra; Yongquan XueORCID; Missagh MehdipourORCID

<jats:title>Abstract</jats:title> <jats:p>The shape of the ambient circumnuclear medium (ACM) density profile can probe the history of accretion onto the central supermassive black holes in galaxies and the circumnuclear environment. However, due to the limitations of instrument resolution, the density profiles of the ACM for most galaxies remain largely unknown. In this work, we propose a novel method to measure the ACM density profile of active galactic nuclei (AGNs) by the equilibrium between the radiation pressure on the warm absorbers (WAs, a type of AGN outflow) and the drag pressure from the ACM. We study the correlation between the outflow velocity and ionization parameter of WAs in each of the five Seyfert 1 galaxies (NGC 3227, NGC 3783, NGC 4051, NGC 4593, and NGC 5548), inferring that the density profile of the ACM is between <jats:italic>n</jats:italic> ∝ <jats:italic>r</jats:italic> <jats:sup>−1.7</jats:sup> and <jats:italic>n</jats:italic> ∝ <jats:italic>r</jats:italic> <jats:sup>−2.15</jats:sup> (<jats:italic>n</jats:italic> is number density and <jats:italic>r</jats:italic> is distance) from 0.01 pc to parsec scales in these five AGNs. Our results indicate that the ACM density profile in Seyfert 1 galaxies is steeper than the prediction by the spherically symmetric Bondi accretion model and the simulated results of the hot accretion flow, but more in line with the prediction by the standard thin-disk model.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 7

First Images of Phosphorus Molecules toward a Protosolar Analog

Jennifer B. BergnerORCID; Andrew M. BurkhardtORCID; Karin I. ÖbergORCID; Thomas S. RiceORCID; Edwin A. BerginORCID

<jats:title>Abstract</jats:title> <jats:p>The chemistry of phosphorus in star- and planet-forming regions is poorly understood, despite the central role of phosphorus in terrestrial biochemistry. We present Atacama Large Millimeter/submillimeter Array band 3 and 4 observations of PO and PN toward the Class I protostar B1-a, representing the first spatially resolved observations of phosphorus carriers toward a solar-type star-forming region. The phosphorus molecules emit from two distinct clumps, which coincide with regions where the protostellar outflow (traced by SiO) interacts with a filament of dense gas (traced by CCS). Thus, the gas-phase phosphorus seems to originate from the shocking of dense interstellar clumps. Based on the observed emission patterns, PO and PN appear to be daughter products of a solid phosphorus carrier with an intermediate volatility between ices and silicate grains. Interstellar shocks may therefore play an important role in converting semi-refractory phosphorus to a more volatile form prior to incorporation into cometary ices. Indeed, the (PO+PN)/CH<jats:sub>3</jats:sub>OH ratio is similar in B1-a and comet 67P, implying a comparable reservoir of volatile phosphorus. The PO/PN ratio ranges from ∼1–8 across B1-a. The northern emission clump exhibits a lower PO/PN ratio and weaker <jats:sup>13</jats:sup>CH<jats:sub>3</jats:sub>OH emission than southern clump, indicating distinct shock physics and chemistry at the two positions. Resolved observations of P carriers toward additional sources are needed to better understand what regulates such variations in the PO/PN ratio in protostellar environments.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 7

New Time-resolved, Multi-band Flares in the GJ 65 System with gPhoton

Scott W. FlemingORCID; Chase MillionORCID; Rachel A. OstenORCID; Dmitrii Y. KolotkovORCID; C. E. BrasseurORCID

<jats:title>Abstract</jats:title> <jats:p>Characterizing the distribution of flare properties and occurrence rates is important for understanding habitability of M-dwarf exoplanets. The Galaxy Evolution Explorer (GALEX) space telescope observed the GJ 65 system, composed of the active, flaring M stars BL Cet and UV Cet, for 15,900 s (∼4.4 hr) in two ultraviolet (UV) bands. The contrast in flux between flares and the photospheres of cool stars is maximized at UV wavelengths, and GJ 65 is the brightest and nearest flaring M-dwarf system with significant GALEX coverage. It therefore represents the best opportunity to measure low-energy flares with GALEX. We construct high-cadence lightcurves from calibrated photon events and find 13 new flare events with near-UV (NUV) energies ranging from 10<jats:sup>28.5</jats:sup>–10<jats:sup>29.5</jats:sup> erg and recover one previously reported flare with an energy of 10<jats:sup>31</jats:sup> erg. The newly reported flares are among the smallest M-dwarf flares observed in the UV with sufficient time resolution to discern lightcurve morphology. The estimated flare frequency at these low energies is consistent with extrapolation from the distributions of higher-energy flares on active M dwarfs measured by other surveys. The largest flare in our sample is bright enough to exceed the local nonlinearity threshold of the GALEX detectors, which precludes color analysis. However, we detect quasi-periodic pulsations during this flare in both the far-UV and NUV bands at a period of ∼50 s, which we interpret as a modulation of the flare’s chromospheric thermal emission through periodic triggering of reconnection by external MHD oscillations in the corona.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 8

Current Challenges in Cepheid Distance Calibrations Using Gaia Early Data Release 3

Kayla A. OwensORCID; Wendy L. FreedmanORCID; Barry F. MadoreORCID; Abigail J. LeeORCID

<jats:title>Abstract</jats:title> <jats:p>Using parallaxes from Gaia Early Data Release 3 (EDR3), we determine multi-wavelength <jats:italic>BVI</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub>, <jats:italic>JHK</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>, and [3.6] and [4.5] micron absolute magnitudes for 37 nearby Milky Way Cepheids, covering the period range between 5 and 60 days. We apply these period–luminosity relations to Cepheids in the Large and Small Magellanic Clouds and find that the derived distances are significantly discrepant with the geometric distances according to detached eclipsing binaries (DEBs). We explore several potential causes of these issues, including reddening, metallicity, and the existence of an additional zero-point offset, but none provide a sufficient reconciliation with both DEB distances. We conclude that the combination of the systematic uncertainties on the EDR3 parallaxes with the uncertainties on the effect of metallicity on the Cepheid distance scale leads to a systematic error floor of approximately 3%. We therefore find that the EDR3 data are not sufficiently accurate in the regime of these bright Cepheids to determine extragalactic distances precise to the 1% level at this time, in agreement with a number of contemporary studies.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 8

Constraining the Cosmic Baryon Distribution with Fast Radio Burst Foreground Mapping

Khee-Gan LeeORCID; Metin AtaORCID; Ilya S. KhrykinORCID; Yuxin HuangORCID; J. Xavier ProchaskaORCID; Jeff CookeORCID; Jielai ZhangORCID; Adam BattenORCID

<jats:title>Abstract</jats:title> <jats:p>The dispersion measure of fast radio bursts (FRBs) encodes the integrated electron density along the line of sight, which is typically dominated by the intergalactic medium contribution in the case of extragalactic FRBs. In this paper, we show that incorporating wide-field spectroscopic galaxy survey data in the foreground of localized FRBs can significantly improve constraints on the partition of diffuse cosmic baryons. Using mock dispersion measures and realistic light-cone galaxy catalogs derived from the Millennium simulation, we define spectroscopic surveys that can be carried out with 4 and 8 m class wide-field spectroscopic facilities. On these simulated surveys, we carry out Bayesian density reconstructions in order to estimate the foreground matter density field. In comparison with the “true” matter density field, we show that these can help reduce the uncertainties in the foreground structures by ∼2–3× compared to cosmic variance. We calculate the Fisher matrix to forecast that <jats:italic>N</jats:italic> = 30 (96) localized FRBs should be able to constrain the diffuse cosmic baryon fraction to ∼10% (∼5%) and parameters governing the size and baryon fraction of galaxy circumgalactic halos to within ∼20%–25% (∼8%–12%). From the Fisher analysis, we show that the foreground data increase the sensitivity of localized FRBs toward our parameters of interest by ∼25×. We briefly introduce FLIMFLAM, an ongoing galaxy redshift survey that aims to obtain foreground data on ∼30 localized FRB fields.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 9

The Gas–Star Formation Cycle in Nearby Star-forming Galaxies. II. Resolved Distributions of CO and Hα Emission for 49 PHANGS Galaxies

Hsi-An Pan; 璽安 潘ORCID; Eva SchinnererORCID; Annie HughesORCID; Adam LeroyORCID; Brent GrovesORCID; Ashley Thomas BarnesORCID; Francesco BelfioreORCID; Frank BigielORCID; Guillermo A. BlancORCID; Yixian CaoORCID; Mélanie ChevanceORCID; Enrico CongiuORCID; Daniel A. DaleORCID; Cosima Eibensteiner; Eric EmsellemORCID; Christopher M. FaesiORCID; Simon C. O. GloverORCID; Kathryn GrashaORCID; Cinthya N. Herrera; I-Ting HoORCID; Ralf S. KlessenORCID; J. M. Diederik KruijssenORCID; Philipp LangORCID; Daizhong LiuORCID; Rebecca McElroy; Sharon E. MeidtORCID; Eric J. MurphyORCID; Jérôme PetyORCID; Miguel QuerejetaORCID; Alessandro Razza; Erik RosolowskyORCID; Toshiki SaitoORCID; Francesco SantoroORCID; Andreas Schruba; Jiayi SunORCID; Neven TomičićORCID; Antonio UseroORCID; Dyas UtomoORCID; Thomas G. WilliamsORCID

<jats:title>Abstract</jats:title> <jats:p>The relative distribution of molecular gas and star formation in galaxies gives insight into the physical processes and timescales of the cycle between gas and stars. In this work, we track the relative spatial configuration of CO and H<jats:italic>α</jats:italic> emission at high resolution in each of our galaxy targets and use these measurements to quantify the distributions of regions in different evolutionary stages of star formation: from molecular gas without star formation traced by H<jats:italic>α</jats:italic> to star-forming gas, and to H <jats:sc>ii</jats:sc> regions. The large sample, drawn from the Physics at High Angular resolution in Nearby GalaxieS ALMA and narrowband H<jats:italic>α</jats:italic> (PHANGS-ALMA and PHANGS-H<jats:italic>α</jats:italic>) surveys, spans a wide range of stellar masses and morphological types, allowing us to investigate the dependencies of the gas‒star formation cycle on global galaxy properties. At a resolution of 150 pc, the incidence of regions in different stages shows a dependence on stellar mass and Hubble type of galaxies over the radial range probed. Massive and/or earlier-type galaxies in our sample exhibit a significant reservoir of molecular gas without star formation traced by H<jats:italic>α</jats:italic>, while lower-mass galaxies harbor substantial H <jats:sc>ii</jats:sc> regions that may have dispersed their birth clouds or formed from low-mass, more isolated clouds. Galactic structures add a further layer of complexity to the relative distribution of CO and H<jats:italic>α</jats:italic> emission. Trends between galaxy properties and distributions of gas traced by CO and H<jats:italic>α</jats:italic> are visible only when the observed spatial scale is ≪500 pc, reflecting the critical resolution requirement to distinguish stages of the star formation process.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 9