The primary purpose of this paper is to see how well a recently proposed new model fits (a) the position of the baryon acoustic oscillation (BAO) features observed in the large-scale distribution of galaxies and (b) the angular size measured for the sound horizon due to BAO imprinted in the cosmic microwave background (CMB) anisotropy. The new model is a hybrid model that combines the tired light (TL) theory with a variant of the ΛCDM model in which the cosmological constant is replaced with a covarying coupling constants' (CCC) parameter α. This model, dubbed the CCC+TL model, can fit the Type Ia supernovae Pantheon+ data as accurately as the ΛCDM model, and also fit the angular size of cosmic dawn galaxies observed by the James Webb Space Telescope, which is in tension with the ΛCDM model. The results we obtained are 151.0 (±5.1) Mpc for the absolute BAO scale at the current epoch, and the angular size of the sound horizon θsh = 060, matching Planck's observations at the surface of the last scattering when the baryon density is set to 100% of the matter density and ∣α∣ is increased by 5.6%. It remains to be seen if the new model is consistent with the CMB power spectrum, the Big Bang nucleosynthesis of light elements, and other critical observations.
The American Astronomical Society (AAS), established in 1899 and based in Washington, DC, is the major organization of professional astronomers in North America. Its membership of about 7,000 individuals also includes physicists, mathematicians, geologists, engineers, and others whose research and educational interests lie within the broad spectrum of subjects comprising contemporary astronomy. The mission of the AAS is to enhance and share humanity's scientific understanding of the universe.
The Institute of Physics (IOP) is a leading scientific society promoting physics and bringing physicists together for the benefit of all. It has a worldwide membership of around 50 000 comprising physicists from all sectors, as well as those with an interest in physics. It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. Its publishing company, IOP Publishing, is a world leader in professional scientific communications.
ISSN: 1538-4357
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.
Remembering Judy Pipher (1940–2022)
GOLD OPEN ACCESS FROM 1 JANUARY 2022
Open all abstracts, in this tab
Rajendra P. Gupta 2024 ApJ 964 55
Olivia A. Greene et al 2021 ApJ 910 162
Post-starburst galaxies are crucial to disentangling the effect of star formation and quenching on galaxy demographics. They comprise, however, a heterogeneous population of objects, described in numerous ways. To obtain a well-defined and uncontaminated sample, we take advantage of spatially resolved spectroscopy to construct an unambiguous sample of E + A galaxies—post-starburst systems with no observed ongoing star formation. Using data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Survey, in the fourth generation of the Sloan Digital Sky Survey (SDSS-IV), we have identified 30 E + A galaxies that lie within the green valley of color–stellar mass space. We first identified E + A candidates by their central, single-fiber spectra and (u–r) color from SDSS DR15, and then further required each galaxy to exhibit E + A properties throughout the entirety of the system to three effective radii. We describe our selection criteria in detail, note common pitfalls in E + A identification, and introduce the basic characteristics of the sample. We will use this E + A sample, which has been assembled with stringent criteria and thus re-establishes a well-defined subpopulation within the broader category of post-starburst galaxies, to study the evolution of galaxies and their stellar populations in the time just after star formation within them is fully quenched.
Minghao Yue et al 2024 ApJ 966 176
We report JWST/NIRCam measurements of quasar host galaxy emissions and supermassive black hole (SMBH) masses for six quasars at 5.9 < z < 7.1 in the Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization (EIGER) project. We obtain deep NIRCam imaging in the F115W, F200W, and F356W bands, as well as F356W grism spectroscopy of the quasars. We use bright unsaturated stars to construct models of the point-spread functions (PSFs) and estimate the errors of these PSFs. We then measure or constrain the fluxes and morphology of the quasar host galaxies by fitting the quasar images as a point source plus an exponential disk. We successfully detect the host galaxies of three quasars, which have host-to-quasar-flux ratios of ∼1%–5%. Spectral energy distribution fitting suggests that these quasar host galaxies have stellar masses of M* ≳ 1010M⊙. For quasars with host galaxy nondetections, we estimate the upper limits of their stellar masses. We use the grism spectra to measure the Hβ line profile and the continuum luminosity, then estimate the SMBH masses for the quasars. Our results indicate that the positive relation between SMBH masses and host galaxy stellar masses already exists at redshift z ≳ 6. The quasars in our sample show a high BH-to-stellar-mass ratio of MBH/M* ∼ 0.15, which is about ∼2 dex higher than local relations. We find that selection effects only contribute partially to the high MBH/M* ratios of high-redshift quasars. This result hints at a possible redshift evolution of the MBH–M* relation.
J. Xu and J. L. Han 2024 ApJ 966 240
The magnetic fields in our Milky Way can be revealed by the distribution of Faraday rotation measures (RMs) of radio sources behind the Galaxy and of radio pulsars inside the Galaxy. Based on the antisymmetry of the Faraday sky in the inner Galaxy to the Galactic coordinates, the magnetic field toroids above and below the Galactic plane with reversed field directions exist in the Galactic halo and have been included in almost all models for the global magnetic structure in the Milky Way. However, the quantitative parameters—such as the field strength, the scale height, and the scale radius of the toroids—are hard to determine from observational data. It has long been argued that the RM antisymmetry could be dominated by the local contributions of the interstellar medium. Here, we get the local-discounted RM contributions from the RM sky and RMs of pulsars and get the first quantitative estimate of the sizes of the magnetic toroids in the Galactic halo. They are huge, starting from a Galactocentric radius of less than 2 kpc and extending to at least 15 kpc, without field direction reversals. Such magnetic toroids in the Galactic halo should naturally constrain the physical processes in galaxies.
A. S. Hales et al 2024 ApJ 966 96
We present Atacama Large Millimeter/submillimeter Array 12-m, 7-m, and Total Power Array observations of the FU Orionis outbursting system, covering spatial scales ranging from 160 to 25,000 au. The high-resolution interferometric data reveal an elongated 12CO(2–1) feature previously observed at lower resolution in 12CO(3–2). Kinematic modeling indicates that this feature can be interpreted as an accretion streamer feeding the binary system. The mass infall rate provided by the streamer is significantly lower than the typical stellar accretion rates (even in quiescent states), suggesting that this streamer alone is not massive enough to sustain the enhanced accretion rates characteristic of the outbursting class prototype. The observed streamer may not be directly linked to the current outburst, but rather a remnant of a previous, more massive streamer that may have contributed enough to the disk mass to render it unstable and trigger the FU Orionis outburst. The new data detect, for the first time, a vast, slow-moving carbon monoxide molecular outflow emerging from this object. To accurately assess the outflow properties (mass, momentum, and kinetic energy), we employ 13CO(2–1) data to correct for optical depth effects. The analysis indicates that the outflow corresponds to swept-up material not associated with the current outburst, similar to the slow molecular outflows observed around other FUor and Class I protostellar objects.
R. Brent Tully et al 2023 ApJ 954 169
Theory of the physics of the early hot universe leads to a prediction of baryon acoustic oscillations (BAOs) that has received confirmation from the pairwise separations of galaxies in samples of hundreds of thousands of objects. Evidence is presented here for the discovery of a remarkably strong individual contribution to the BAO signal at z = 0.068, an entity that is given the name Ho'oleilana. The radius of the 3D structure is Mpc. At its core is the Boötes supercluster. The Sloan Great Wall, Center for Astrophysics Great Wall, and Hercules complex all lie within the BAO shell. The interpretation of Ho'oleilana as a BAO structure with our preferred analysis implies a value of the Hubble constant of
Yusuke Sakai et al 2023 ApJ 951 59
Richardson–Lucy (RL) deconvolution is one of the classical methods widely used in X-ray astronomy and other areas. Amid recent progress in image processing, RL deconvolution still leaves much room for improvement under realistic situations. One direction is to include the positional dependence of a point-spread function (PSF), so-called RL deconvolution with a spatially variant PSF (RLsv). Another is the method of estimating a reliable number of iterations and their associated uncertainties. We developed a practical method that incorporates the RLsv algorithm and the estimation of uncertainties. As a typical example of bright and high-resolution images, the Chandra X-ray image of the supernova remnant Cassiopeia A was used in this paper. RLsv deconvolution enables us to uncover the smeared features in the forward/backward shocks and jet-like structures. We constructed a method to predict the appropriate number of iterations using statistical fluctuation of the observed images. Furthermore, the uncertainties were estimated by error propagation from the last iteration, which was phenomenologically tested with the observed data. Thus, our method is a practically efficient framework to evaluate the time evolution of the remnants and their fine structures embedded in high-resolution X-ray images.
Željko Ivezić et al 2019 ApJ 873 111
We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2 field of view, a 3.2-gigapixel camera, and six filters (ugrizy) covering the wavelength range 320–1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ∼ 27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.
Jon Hakkila et al 2024 ApJ 966 13
We propose that gamma-ray burst (GRB) pulses are produced when highly relativistic jets sweep across an observer's line of sight. We hypothesize that axisymmetric jet profiles, coupled with special relativistic effects, produce the time-reversed properties of GRB pulses. Curvature resulting from rapid jet expansion is responsible for much of the observed pulse asymmetry and hard-to-soft evolution. The relative obliqueness with which the jet crosses the line of sight explains the known GRB pulse morphological types. We explore two scenarios: one in which a rigid/semirigid jet moves laterally and another in which a ballistic jet sprays material from a laterally moving nozzle. The ballistic jet model is favored based upon its consistency with standard emission mechanisms.
Jacob Pilawa et al 2024 ApJ 966 205
Evidence for the majority of the supermassive black holes in the local Universe has been obtained dynamically from stellar motions with the Schwarzschild orbit superposition method. However, there have been only a handful of studies using simulated data to examine the ability of this method to reliably recover known input black hole masses MBH and other galaxy parameters. Here, we conduct a comprehensive assessment of the reliability of the triaxial Schwarzschild method at simultaneously determining MBH, stellar mass-to-light ratio M*/L, dark matter mass, and three intrinsic triaxial shape parameters of simulated galaxies. For each of 25 rounds of mock observations using simulated stellar kinematics and the TriOS code, we derive best-fitting parameters and confidence intervals after a full search in the 6D parameter space with our likelihood-based model inference scheme. The two key mass parameters, MBH and M*/L, are recovered within the 68% confidence interval, and other parameters are recovered between the 68% and 95% confidence intervals. The spatially varying velocity anisotropy of the stellar orbits is also well recovered. We explore whether the goodness-of-fit measure used for galaxy model selection in our pipeline is biased by variable complexity across the 6D parameter space. In our tests, adding a penalty term to the likelihood measure either makes little difference, or worsens the recovery in some cases.
Open all abstracts, in this tab
Intae Jung et al 2024 ApJ 967 73
We analyze rest-frame ultraviolet to optical spectra of three z ≃ 7.47–7.75 galaxies whose Lyα emission lines were previously detected with Keck/MOSFIRE observations, using the JWST/NIRSpec observations from the Cosmic Evolution Early Release Science survey. From NIRSpec data, we confirm the systemic redshifts of these Lyα emitters, and emission-line ratio diagnostics indicate these galaxies were highly ionized and metal-poor. We investigate Lyα line properties, including the line flux, velocity offset, and spatial extent. For the one galaxy where we have both NIRSpec and MOSFIRE measurements, we find a significant offset in their flux measurements (∼1.3–5× greater in MOSFIRE) and a marginal difference in the velocity shifts. The simplest interpretation is that the Lyα emission is extended and not entirely encompassed by the NIRSpec slit. The cross-dispersion profiles in NIRSpec reveal that Lyα in one galaxy is significantly more extended than the nonresonant emission lines. We also compute the expected sizes of ionized bubbles that can be generated by the Lyα sources and discuss viable scenarios for the creation of sizable ionized bubbles (>1 physical Mpc). The source with the highest-ionization condition is possibly capable of ionizing its own bubble, while the other two do not appear to be capable of ionizing such a large region, but require additional sources of ionizing photons. Therefore, the fact that we detect Lyα from these galaxies suggests diverse scenarios for the escape of Lyα during the epoch of reionization. High-spectral-resolution spectra with JWST/NIRSpec will be extremely useful for constraining the physics of patchy reionization.
Georgios Zacharegkas et al 2024 ApJ 967 71
The nonresonant streaming instability (Bell instability) plays a pivotal role in the acceleration and confinement of cosmic rays (CRs), yet the exact mechanism responsible for its saturation and the magnitude of the final amplified magnetic field have not been assessed from first principles. Using a survey of hybrid simulations (with kinetic ions and fluid electrons), we study the evolution of the Bell instability as a function of the parameters of the CR population. We find that at saturation, the magnetic pressure in the amplified field is comparable with the initial CR anisotropic pressure, rather than with the CR energy flux, as previously argued. These results provide a predictive prescription for the total magnetic field amplification expected in the many astrophysical environments where the Bell instability is important.
Sean M. Ressler et al 2024 ApJ 967 70
Perturber objects interacting with supermassive black hole accretion disks are often invoked to explain observed quasiperiodic behavior in active galactic nuclei (AGN). We present global, 3D general relativistic magnetohydrodynamic (GRMHD) simulations of black holes on inclined orbits colliding with magnetically arrested thick AGN disks using a binary black hole spacetime with mass ratio 0.1. We do this by implementing an approximate time-dependent binary black hole metric into the GRMHD Athena++ code. The secondary enhances the unbound mass outflow rate 2–4 times above that provided by the disk in quasiperiodic outbursts, eventually merging into a more continuous outflow at larger distances. We present a simple analytic model that qualitatively agrees well with this result and can be used to extrapolate to unexplored regions of parameter space. We show self-consistently for the first time that spin–orbit coupling between the primary black hole spin and the binary orbital angular momentum causes the accretion disk and jet directions to precess significantly (by 60°–80°) on long timescales (e.g., ∼20 times the binary orbital period). Because this effect may be the only way for thick AGN disks to consistently precess, it could provide strong evidence of a secondary black hole companion if observed in such a system. Besides this new phenomenology, the time-average properties of the disk and accretion rates onto the primary are only marginally altered by the presence of the secondary, consistent with our estimate for a perturbed thick disk. This situation might drastically change in cooled thin disks.
S. Jane Arthur et al 2024 ApJ 967 69
The kinetic energy in tidal flows, when converted into heat, can affect the internal structure of a star and shift its location on a color–magnitude diagram from that of standard models. In this paper we explore the impact of injecting heat into stars with masses near the main-sequence turnoff mass (1.26 M⊙) of the open cluster M67. The heating rate is obtained from the tidal shear energy dissipation rate, which is calculated from first principles by simultaneously solving the equations that describe orbital motion and the response of a star's layers to the gravitational, Coriolis, centrifugal, gas pressure, and viscous forces. The stellar structure models are computed with MESA. We focus on the effects of injecting heat in pulses lasting 0.01 Gyr, a time frame consistent with the synchronization timescale in binary systems. We find that the location of the tidally perturbed stars in the M67 color–magnitude diagram is shifted to significantly higher luminosities and effective temperatures than predicted by the standard model isochrone and includes locations corresponding to some of the blue straggler stars. Because tidal heating takes energy from the orbit, causing it to shrink, blue straggler stars could be merger or mass transfer progenitors, as well as products of these processes.
Claudio Hernández-Vera et al 2024 ApJ 967 68
H2CO is a small organic molecule widely detected in protoplanetary disks. As a precursor to grain-surface formation of CH3OH, H2CO is considered an important precursor of O-bearing organic molecules that are locked in ices. Still, since gas-phase reactions can also form H2CO, there remains an open question on the channels by which organics form in disks, and how much the grain versus the gas pathways impact the overall organic reservoir. We present spectrally and spatially resolved Atacama Large Millimeter/submillimeter Array observations of several ortho- and para-H2CO transitions toward the bright protoplanetary disk around the Herbig Ae star HD 163296. We derive column density, excitation temperature, and ortho-to-para ratio (OPR) radial profiles for H2CO, as well as disk-averaged values of NT ∼ 4 × 1012 cm−2, Tex ∼ 20 K, and OPR ∼ 2.7, respectively. We empirically determine the vertical structure of the emission, finding vertical heights of z/r ∼ 0.1. From the profiles, we find a relatively constant OPR ∼ 2.7 with radius, but still consistent with 3.0 among the uncertainties, a secondary increase of NT in the outer disk, and low Tex values that decrease with disk radius. Our resulting radial, vertical, and OPR constraints suggest an increased UV penetration beyond the dust millimeter edge, consistent with an icy origin but also with cold gas-phase chemistry. This Herbig disk contrasts previous results for the T Tauri disk, TW Hya, which had a larger contribution from cold gas-phase chemistry. More observations of other sources are needed to disentangle the dominant formation pathway of H2CO in protoplanetary disks.