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.
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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.
Saiyang Zhang et al 2024 ApJ 965 121
Supermassive dark stars (SMDS) are luminous stellar objects formed in the early Universe at redshift z ∼ 10–20, made primarily of hydrogen and helium, yet powered by dark matter. We examine the capabilities of the Roman Space Telescope (RST), and find it able to identify ∼106M⊙ SMDSs at redshifts up to z ≃ 14. With a gravitational lensing factor of μ ∼ 100, RST could identify SMDS as small as ∼104M⊙ at z ∼ 12 with ∼106 s exposure. Differentiating SMDSs from early galaxies containing zero metallicity stars at similar redshifts requires spectral, photometric, and morphological comparisons. With only RST, the differentiation of SMDS, particularly those formed via adiabatic contraction with M ≳ 105M⊙ and lensed by μ ≳ 100, is possible due to their distinct photometric signatures from the first galaxies. Those formed via dark matter capture can be differentiated only by image morphology: i.e., point object (SMDSs) versus extended object (sufficiently magnified galaxies). By additionally employing James Webb Space Telescope (JWST) spectroscopy, we can identify the He iiλ1640 absorption line, a smoking gun for SMDS detection. Although RST does not cover the required wavelength band (for zemi ≳ 10), JWST does; hence, the two can be used in tandem to identify SMDS. The detection of SMDS would confirm a new type of star powered by dark matter and may shed light on the origins of the supermassive black holes powering bright quasars observed at z ≳ 6.
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
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.
Xintong Lyu et al 2024 ApJ 964 152
Short-period exoplanets on circular orbits are thought to be tidally locked into synchronous rotation. If tidally locked, these planets must possess permanent day- and night-sides, with extreme irradiation on the dayside and none on the nightside. However, so far the tidal locking hypothesis for exoplanets is supported by little to no empirical evidence. Previous work showed that the super-Earth LHS 3844b likely has no atmosphere, which makes it ideal for constraining the planet's rotation. Here we revisit the Spitzer phase curve of LHS 3844b with a thermal model of an atmosphere-less planet and analyze the impact of nonsynchronous rotation, eccentricity, tidal dissipation, and surface composition. Based on the lack of observed strong tidal heating we rule out rapid nonsynchronous rotation (including a Mercury-like 3:2 spin–orbit resonance) and constrain the planet's eccentricity to less than ∼0.001 (more circular than Io's orbit). In addition, LHS 3844b's phase curve implies that the planet either still experiences weak tidal heating via a small-but-nonzero eccentricity (requiring an undetected orbital companion), or that its surface has been darkened by space weathering; of these two scenarios we consider space weathering more likely. Our results thus support the hypothesis that short-period rocky exoplanets are tidally locked, and further show that space weathering can significantly modify the surfaces of atmosphere-less exoplanets.
Kazuki Tokuda et al 2024 ApJ 965 99
Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations have revealed an increasing number of compact protostellar disks with radii of less than a few tens of astronomical units and that young Class 0/I objects have an intrinsic size diversity. To deepen our understanding of the origin of such tiny disks, we have performed highest-resolution configuration observations with ALMA at a beam size of ∼003 (4 au) on the very low-luminosity Class 0 protostar embedded in the Taurus dense core MC 27/L1521F. The 1.3 mm continuum measurement successfully resolved a tiny, faint (∼1 mJy) disk with a major axis length of ∼10 au, one of the smallest examples in the ALMA protostellar studies. In addition, we detected spike-like components in the northeastern direction at the disk edge. Gravitational instability or other fragmentation mechanisms cannot explain the structures, given the central stellar mass of ∼0.2 M⊙ and the disk mass of ≳10−4M⊙. Instead, we propose that these small spike structures were formed by a recent dynamic magnetic flux transport event due to interchange instability that would be favorable to occur if the parental core has a strong magnetic field. The presence of complex arc-like structures on a larger (∼2000 au) scale in the same direction as the spike structures suggests that the event was not single. Such episodic, dynamical events may play an important role in maintaining the compact nature of the protostellar disk in the complex gas envelope during the main accretion phase.
Marco Martorano et al 2023 ApJ 957 46
We examine the wavelength dependence of radial light profiles based on Sérsic index n measurements of 1067 galaxies with M* ≥ 109.5M⊙ and in the redshift range 0.5 < z < 3. The sample and rest-frame optical light profiles are drawn from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and 3D Hubble Space Telescope (HST); rest-frame near-infrared light profiles are inferred from images collected for the Cosmic Evolution Early Release Science (CEERS) program with the Near Infrared Camera (NIRCam) on board of the James Webb Space Telescope (JWST). n shows only a weak dependence on the wavelength, regardless of the redshift, galaxy mass, and type. On average, star-forming galaxies have n = 1–1.5 and quiescent galaxies have n = 3–4 in the rest-frame optical and near-infrared. The strong correlation at all wavelengths between n and star formation activity implies a physical connection between the radial stellar mass profile and star formation activity. The main caveat is that the current sample is too small to discern trends for the most massive galaxies (M* > 1011M⊙).
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.
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.
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Brian C. Lacki 2024 ApJ 966 183
The search for extraterrestrial intelligence includes efforts to constrain populations of artificial broadcasts in other galaxies. Previous efforts use individualist methods, searching for single broadcasts with high signal-to-noise ratio. These would be detected as observables with extreme values. This approach is limited to very bright broadcasts and also is subject to confusion, where a large number of broadcasts blend together to form a noise continuum. The mean value of the total emission provides an additional collective bound: the luminosity of the transmitters is no higher than the galaxy's observed luminosity. Using the framework developed in Paper I, I evaluate how confusion affects individualist searches. I then compare individualist and collective approaches for radio broadcasts from the Milky Way, M31, and three Virgo Cluster elliptical galaxies. For current observations, confusion blurs narrowband radio broadcasts together in the Virgo ellipticals when there is one broadcast per gigahertz per 1000 stars. The collective bound implies fewer than L-band broadcasts per star per gigahertz in the Milky Way wideband and is about 10 and 400 times stronger in M31 and M59, respectively. Applying the collective bound to the far-infrared–radio correlation yields constraints on radio broadcast populations in star-forming galaxies throughout the Universe. The collective bound allows us to rule out large regions of broadcast population parameter space even for distant galaxies. It also imposes constraints on gamma-ray, neutrino, and gravitational-wave broadcasts in the nearest galaxies.
Brian C. Lacki 2024 ApJ 966 182
Artificial broadcasts from extraterrestrial intelligences are a hypothetical class of celestial phenomena. Unlike known astrophysical objects, the societies that generate them may be able to replicate on galactic scales through interstellar travel. Different galaxies could thus have drastically different populations, with variations in abundance of many orders of magnitude. I present a probabilistic formalism to treat this shared history, in which societies and their broadcasts are described by distributions over basic properties like lifespan and energy released. The framework contains a hierarchy of objects related by a tree structure. Discrete societies, the sources of broadcasts, are organized into potentially interstellar metasocieties. The population of each type of object is represented by a random point process in an abstract parameter hyperspace, a haystack. When a selection like an observation draws a sample, the point process is thinned. Given assumptions of interchangeability and independence, observables are modeled with compound Poisson random variables. I present an example of how selection bias can favor sampling longer-lived objects. I rederive the Drake equation for societies in the limit of no expansion. When interstellar replication is present, however, the mean number of detected broadcasts can depend quadratically on stellar mass, suggesting a search strategy favoring large galaxies.
Crystal L. Martin et al 2024 ApJ 966 190
We present integral field spectroscopy toward and around J1044+0353, a rapidly growing, low-metallicity galaxy that produces extreme [O iii] line emission. A new map of the O32 flux ratio reveals a density-bounded ionization cone emerging from the starburst. The interaction of the hydrogen-ionizing radiation, produced by the very young starburst, with a cavity previously carved out by a galactic outflow, whose apex lies well outside the starburst region, determines the pathway for global Lyman continuum (LyC) escape. In the region within a few hundred parsecs of the young starburst, we demonstrate that superbubble breakthrough and blowout contribute distinct components to the [O iii] line profile: broad and very broad emission line wings, respectively. We draw attention to the large [O iii] luminosity of the broad component and argue that this emission comes from photoionized, superbubble shells rather than a galactic wind as is often assumed. The spatially resolved He iiλ4686 nebula appears to be photoionized by young star clusters. Stellar wind emission from these stars is likely the source of line wings detected on the He ii line profile. This broader He ii component indicates slow stellar winds, consistent with an increase in stellar rotation (and a decrease in effective escape speed) at the metallicity of J1044+0353. At least in J1044+0353, the recent star formation history plays a critical role in generating a global pathway for LyC escape, and the anisotropic escape would likely be missed by direct observations of the LyC.
Jinshi Sai et al 2024 ApJ 966 192
We present the results of our mosaic observations of a single Class 0 protostar IRAS 15398−3359 with the Atacama Compact Array in the CO J = 2–1 line. The new observations covering a square region reveal elongated redshifted and blueshifted components, which are located at distances of ∼30''–75'' on the northern and southern sides of the protostar, respectively, in addition to the previously observed primary and secondary outflows. These elongated components exhibit Hubble-law-like velocity structures, i.e., an increase of velocity with increasing distance from the protostar, suggesting that they comprise the third outflow associated with the protostar. Besides, a new redshifted component is detected at radii of ∼40''–75'' on the northwestern side of the protostar. This redshifted component also exhibits a Hubble-law-like velocity profile, which could be a counterpart of the secondary outflow mostly detected at blueshifted velocities in a previous study. The three outflows are all misaligned by ∼20°–90°, and the dynamical timescale of the primary outflow is shorter than those of the other outflows, approximately by an order of magnitude. These facts hint that the outflow launch direction has significantly changed with time. The outflow direction may change if the rotational axis and the magnetic field are misaligned or if the dense core is turbulent. We favor the second scenario as the origin of the multiple outflows in IRAS 15398−3359, based on a comparison between the observational results and numerical simulations.
Jeehyun Yang and Renyu Hu 2024 ApJ 966 189
With the advent of JWST and the spectroscopic characterization of exoplanet atmospheres in unprecedented detail, there is a demand for more complete pictures of chemical and photochemical reactions and their impacts on atmospheric composition. Traditionally, building reaction networks for (exo)planetary atmospheres involves manually tracking relevant species and reactions, a time-consuming and error-prone process. This approach's applicability is also often limited to specific conditions, making it less versatile for different planetary types (i.e., photochemical networks for Jupiters may not be directly applicable to water-rich exoplanets). We introduce an automated approach using a computer-aided chemical reaction network generator, combined with a 1D photochemical kinetic-transport model, offering significant advantages. This approach automatically selects reaction rates through a rate-based iterative algorithm and multiple refinement steps, enhancing model reliability. Also, this approach allows for the efficient simulation of diverse chemical environments, from hydrogen to water, carbon dioxide, and nitrogen-dominated atmospheres. Using WASP-39b and WASP-80b as examples, we demonstrate our approach's effectiveness, showing good agreement with recent JWST data. Our WASP-39b model aligns with prior studies and JWST observations, capturing photochemically produced sulfur dioxide. The WASP-80b model reveals an atmosphere influenced by deep-interior thermochemistry and vertical mixing, consistent with JWST NIRCam observations. Furthermore, our model identifies a novel initial step for the N2–NH3–HCN pathway that enhances the efficiency of the conversion in high-temperature/high-pressure environments. This automated chemical network generation offers a novel, efficient, and precise framework for studying exoplanetary atmospheres, marking a significant advancement over traditional modeling techniques.