Papers for Wednesday, Apr 12 2023

Pulsar timing arrays (PTAs) provide a way to detect gravitational waves at nanohertz frequencies. In this band, the most likely signals are stochastic, with a power spectrum that rises steeply at lower frequencies. Indeed, the observation of a common red noise process in pulsar-timing data suggests that the first credible detection of nanohertz-frequency gravitational waves could take place within the next few years. The detection process is complicated by the nature of the signals and the noise: the first observational claims will be statistical inferences drawn at the threshold of detectability. To demonstrate that gravitational waves are creating some of the noise in the pulsar-timing data sets, observations must exhibit the Hellings and Downs curve -- the angular correlation function associated with gravitational waves -- as well as demonstrating that there are no other reasonable explanations. To ensure that detection claims are credible, the International Pulsar Timing Array (IPTA) has a formal process to vet results prior to publication. This includes internal sharing of data and processing pipelines between different PTAs, enabling independent cross-checks and validation of results. To oversee and validate any detection claim, the IPTA has also created an eight-member Detection Committee (DC) which includes four independent external members. IPTA members will only publish their results after a formal review process has concluded. This document is the initial DC checklist, describing some of the conditions that should be fulfilled by a credible detection.

We construct a field-based Bayesian Hierarchical Model for cosmic shear that includes, for the first time, the important astrophysical systematics of intrinsic alignments and baryon feedback, in addition to a gravity model. We add to the BORG-WL framework the tidal alignment and tidal torquing model (TATT) for intrinsic alignments and compare them with the non-linear alignment (NLA) model. With synthetic data, we have shown that adding intrinsic alignments and sampling the TATT parameters does not reduce the constraining power of the method and the field-based approach lifts the weak lensing degeneracy. We add baryon effects at the field level using the enthalpy gradient descent (EGD) model. This model displaces the dark matter particles without knowing whether they belong to a halo and allows for self-calibration of the model parameters, which are inferred from the data. We have also illustrated the effects of model misspecification for the baryons. The resulting model now contains the most important physical effects and is suitable for application to data.

AGN have been generally considered to be less frequent in denser environments due to the lower number of galaxy-galaxy interactions and/or the removal of their gas-rich reservoirs by the dense intergalactic medium. However, recent observational and theoretical works suggest that the effect of ram-pressure stripping might reduce the angular momentum of their gas, causing it to infall towards the super massive black hole (SMBH) at their centre, activating the AGN phase. In this work we explore the connection between environment and nuclear activity by evaluating the variation in the incidence of ionized outflows in AGN across different environments. We select a sample of $\sim3300$ optical AGN from the Sloan Digital Sky Survey Data Release 13 that we match with the group catalogue from Lim et al. 2017. We further probe their environment through the projected distance to the central galaxy of the group/cluster and the projected surface density to the 5th neighbour ($\delta_5$). We find that at lower masses ($<10^{10.3}$M$_{\odot}$), the fraction of ionized outflows is significantly lower in satellite ($\sim7$%) than in isolated ($\sim22$%) AGN. The fraction of outflows in all satellite AGN decreases towards closer distances to the central, whereas only the lower-mass ones display a significant decline with $\delta_5$. Although this study does not include AGN in the densest regions of galaxy clusters, our findings suggest that AGN in dense environments accrete less gas than those in the field potentially due to the removal of the gas reservoirs via stripping or starvation, consistent with a negative connection between environment and AGN activity. We propose that the observed change in the incidence of outflows towards denser regions of groups and clusters could contribute to the higher gas metallicities of cluster galaxies compared to field ones, especially at lower masses.

We present a detailed study of the column density and covering fraction profiles of C IV absorption around 86 redshift $z \approx 3.3$ Ly$\alpha$ emitters (LAEs) detected in 8 Multi-Unit Spectroscopic Explorer (MUSE) fields of $1'\times 1'$ centered on 8 bright background quasars as part of the MUSEQuBES survey. Using Voigt profile fitting of all the C IV absorbers detected along these 8 sightlines, we generated a ``blind'' absorbers' catalog consisting of 489 C IV absorption components. We cross-matched this blind C IV catalog with the MUSE-detected LAE catalog and found a significant enhancement of C IV components within $\approx \pm$400 $\rm km\, s^{-1}$ of the systemic redshifts of the LAEs. Neither the C IV column density ($N$) nor the Doppler parameter ($b$) of individual C IV components shows any significant anti-correlation with impact parameter ($\rho$) of the LAEs in the 68 percentile range of $90\leq \rho \leq 230$ physical kpc (pkpc). We find a covering fraction of $\approx 60\%$ for a threshold $N$(C IV) of $10^{12.5}\, \rm \rm cm^{-2}$, which is roughly twice as high as in random regions. The C IV covering fraction remains constant at $\approx50\%$ for impact parameters in the range 150--250~pkpc ($\approx 3-6 R_{200}$). Using the covering fraction profile, we constrained the LAE--C IV absorber two-point correlation function, and obtained $r_0 = 3.2~h^{-1}$ comoving Mpc (cMpc) and $\gamma = 1.2$ for a threshold $N$(C IV) of $10^{13.0}\, \rm cm^{-2}$. The C IV covering fraction is found to be enhanced for the LAEs that are part of a ``pair/group'' compared to the isolated ones.

The Large Array Survey Telescope (LAST) is a wide-field visible-light telescope array designed to explore the variable and transient sky with a high cadence. LAST will be composed of 48, 28-cm f/2.2 telescopes (32 already installed) equipped with full-frame backside-illuminated cooled CMOS detectors. Each telescope provides a field of view (FoV) of 7.4 deg^2 with 1.25 arcsec/pix, while the system FoV is 355 deg^2 in 2.9 Gpix. The total collecting area of LAST, with 48 telescopes, is equivalent to a 1.9-m telescope. The cost-effectiveness of the system (i.e., probed volume of space per unit time per unit cost) is about an order of magnitude higher than most existing and under-construction sky surveys. The telescopes are mounted on 12 separate mounts, each carrying four telescopes. This provides significant flexibility in operating the system. The first LAST system is under construction in the Israeli Negev Desert, with 32 telescopes already deployed. We present the system overview and performances based on the system commissioning data. The Bp 5-sigma limiting magnitude of a single 28-cm telescope is about 19.6 (21.0), in 20 s (20x20 s). Astrometric two-axes precision (rms) at the bright-end is about 60 (30)\,mas in 20\,s (20x20 s), while absolute photometric calibration, relative to GAIA, provides ~10 millimag accuracy. Relative photometric precision, in a single 20 s (320 s) image, at the bright-end measured over a time scale of about 60 min is about 3 (1) millimag. We discuss the system science goals, data pipelines, and the observatory control system in companion publications.

Dark energy is a premier mystery of physics, both theoretical and experimental. As we look to develop plans for high energy physics over the next decade, within a two decade view, we consider benchmarks for revealing the nature of dark energy. We conclude, based on fundamental physical principles detailed below, that understanding will come from experiments reaching key benchmarks: $\bullet\ \sigma(w_a)<2.5\sigma(w_0)$ $\bullet\ \sigma(w_0)<0.02$ $ \bullet\ \sigma(\rho_{\rm de}/\rho_{\rm crit})<(1/3)\rho_\Lambda/\rho_{\rm crit}$ for all redshifts $z<5$ where the dark energy equation of state $w(a)=w_0+w_a(1-a)$. Beyond the cosmic expansion history we also discuss benchmarks for the cosmic growth history appropriate for testing classes of gravity theories. All benchmarks can be achieved by a robust Stage 5 program, using extensions of existing probes plus the highly complementary, novel probe of cosmic redshift drift.

We present a deep-learning based approach for measuring small planetary radial velocities in the presence of stellar variability. We use neural networks to reduce stellar RV jitter in three years of HARPS-N sun-as-a-star spectra. We develop and compare dimensionality-reduction and data splitting methods, as well as various neural network architectures including single line CNNs, an ensemble of single line CNNs, and a multi-line CNN. We inject planet-like RVs into the spectra and use the network to recover them. We find that the multi-line CNN is able to recover planets with 0.2 m/s semi-amplitude, 50 day period, with 8.8% error in the amplitude and 0.7% in the period. This approach shows promise for mitigating stellar RV variability and enabling the detection of small planetary RVs with unprecedented precision.

A significant challenge in radiative transfer theory for atmospheres of exoplanets and brown dwarfs is the derivation of computationally efficient methods that have adequate fidelity to more precise, numerically demanding solutions. In this work, we extend the capability of the first open-source radiative transfer model for computing the reflected light of exoplanets at any phase geometry, PICASO: Planetary Intensity Code for Atmospheric Spectroscopy Observations. Until now, PICASO has implemented two-stream approaches to the solving the radiative transfer equation for reflected light, in particular following the derivations of Toon et al. (1989) (Toon89). In order to improve the model accuracy, we have considered higher-order approximations of the phase functions, namely, we have increased the order of approximation from 2 to 4, using spherical harmonics. The spherical harmonics approximation decouples spatial and directional dependencies by expanding the intensity and phase function into a series of spherical harmonics, or Legendre polynomials, allowing for analytical solutions for low-order approximations to optimize computational efficiency. We rigorously derive the spherical harmonics method for reflected light and benchmark the 4-term method (SH4) against Toon89 and two independent and higher-fidelity methods (CDISORT & doubling-method). On average, the SH4 method provides an order of magnitude increase in accuracy, compared to Toon89. Lastly, we implement SH4 within PICASO and observe only modest increase in computational time, compared to two-stream methods (20% increase).

Approximate methods to estimate solutions to the radiative transfer equation are essential for the understanding of atmospheres of exoplanets and brown dwarfs. The simplest and most popular choice is the "two-stream method" which is often used to produce simple yet effective models for radiative transfer in scattering and absorbing media. Toon et al. (1989) (Toon89) outlined a two-stream method for computing reflected light and thermal spectra and was later implemented in the open-source radiative transfer model PICASO. In Part~I of this series, we developed an analytical spherical harmonics method for solving the radiative transfer equation for reflected solar radiation (Rooney et al. 2023), which was implemented in PICASO to increase the accuracy of the code by offering a higher-order approximation. This work is an extension of this spherical harmonics derivation to study thermal emission spectroscopy. We highlight the model differences in the approach for thermal emission and benchmark the 4-term method (SH4) against Toon89 and a high-stream discrete-ordinates method, CDISORT. By comparing the spectra produced by each model we demonstrate that the SH4 method provides a significant increase in accuracy, compared to Toon89, which can be attributed to the increased order of approximation and to the choice of phase function. We also explore the trade-off between computational time and model accuracy. We find that our 4-term method is twice as slow as our 2-term method, but is up to five times more accurate, when compared with CDISORT. Therefore, SH4 provides excellent improvement in model accuracy with minimal sacrifice in numerical expense.

The direct comparison between hydrodynamical simulations and observations is needed to improve the physics included in the former and test biases in the latter. Post-processing radiative transfer and synthetic observations are now the standard way to do this. We report on the first application of the \texttt{SKIRT} radiative transfer code to simulations of a star-forming cloud. The synthetic observations are then analyzed following traditional observational workflows. We find that in the early stages of the simulation, stellar radiation is inefficient in heating dust to the temperatures observed in Galactic clouds, thus the addition of an interstellar radiation field is necessary. The spectral energy distribution of the cloud settles rather quickly after $\sim3$ Myr of evolution from the onset of star formation, but its morphology continues to evolve for $\sim8$ Myr due to the expansion of \textsc{Hii} regions and the respective creation of cavities, filaments, and ridges. Modeling synthetic \textit{Herschel} fluxes with 1- or 2-component modified black bodies underestimates total dust masses by a factor of $\sim2$. Spatially-resolved fitting recovers up to about $70\%$ of the intrinsic value. This ``missing mass'' is located in a very cold dust component with temperatures below $10$ K, which does not contribute appreciably to the far-infrared flux. This effect could bias real observations if such dust exists in large amounts. Finally, we tested observational calibrations of the SFR based on infrared fluxes and concluded that they are in agreement when compared to the intrinsic SFR of the simulation averaged over $\sim100$ Myr.

The early evolution of the Earth-Moon system prescribes the tidal environment of the Hadean Earth and holds the key to the formation mechanism of the Moon and its thermal evolution. Estimating its early state by backtracking from the present, however, suffers from substantial uncertainties associated with ocean tides. Tidal evolution during the solidification of Earth's magma ocean, on the other hand, has the potential to provide robust constraints on the Earth-Moon system before the appearance of a water ocean. Here we show that energy dissipation in a solidifying magma ocean results in considerably more limited lunar recession than previously thought, and that the Moon was probably still at the distance of $\sim$7-9 Earth radii at the end of solidification. This limited early recession aggravates the often overlooked difficulty of modeling tidal dissipation in Earth's first billion years, but it also offers a new possibility of resolving the lunar inclination problem by allowing the operation of multiple excitation mechanisms.

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.

We analyzed All-Sky Automated Survey for Supernovae (ASAS-SN), Asteroid Terrestrial-impact Last Alert System (ATLAS) and Transiting Exoplanet Survey Satellite (TESS) observations of CM Mic and found that this object belongs to a small group of ER UMa stars showing standstills. In addition to typical ER UMa-type cycles, the object showed standstills between 2017 and 2019 July, and in 2022. The supercycles varied between 49 and 83 d. In 2015, the object showed outbursts with a cycle length of ~35 d. An analysis of TESS observations during the 2020 July outburst detected superhumps with a mean period of 0.080251(6) d (value after the full development of superhumps). We also studied other ER UMa stars showing standstills mainly using Zwicky Transient Facility (ZTF) data. DDE 48, MGAB-V728 and ZTF18abmpkbj mostly showed ER UMa-type supercycles but showed one or two standstills. MGAB-V3488 was mostly in ER UMa states with short (~25 d) supercycles in 2020-2022 similar to RZ LMi. This object also showed long standstills. PS1-3PI J181732.65+101954.6 showed ER UMa-type supercycles up to 2020 May and entered a long standstill. ZTF18abncpgs showed standstills most of the time, but also showed ER UMa-type supercycles occasionally between standstills. ZTF19aarsljl is a likely member of this group. MGAB-V284 showed a pattern similar to ER UMa stars showing standstills but with a longer time-scale of normal outbursts. This object seems to be an ER UMa star with standstills above the period gap. None of the objects we studied showed a superoutburst arising from a long standstill, as recorded in NY Ser in 2018, although the 2019 June-July superoutburst of PS1-3PI J181732.65+101954.6 might have been an exception.

Understanding dark matter is one of the most urgent questions in modern physics. A very interesting candidate is primordial black holes (PBHs; Carr2016). For the mass ranges of $< 10^{-16} M_{\odot}$ and $> 100 M_{\odot}$, PBHs have been ruled out. However, they are still poorly constrained in the mass ranges of $10^{-16} - 100 M_{\odot}$ (Belotsky et al. 2019). Fast radio bursts (FRBs) are millisecond flashes of radio light of unknown origin mostly from outside the Milky Way. Due to their short timescales, gravitationally lensed FRBs, which are yet to be detected, have been proposed as a useful probe for constraining the presence of PBHs in the mass window of $< 100M_{\odot}$ (Mu\~noz et al. 2016). Up to now, the most successful project in finding FRBs has been CHIME. Due to its large field of view (FoV), CHIME is detecting at least 600 FRBs since 2018. However, none of them is confirmed to be gravitationally lensed (Leung et al. 2022). Taiwan plans to build a new telescope, BURSTT dedicated to detecting FRBs. Its survey area will be 25 times greater than CHIME. BURSTT can localize all of these FRBs through very-long-baseline interferometry (VLBI). We estimate the probability to find gravitationally lensed FRBs, based on the scaled redshift distribution from the latest CHIME catalog and the lensing probability function from Mu\~noz et al. (2016). BURSTT-2048 can detect ~ 24 lensed FRBs out of ~ 1,700 FRBs per annum. With BURSTT's ability to detect nanosecond FRBs, we can constrain PBHs to form a part of dark matter down to $10^{-4}M_{\odot}$.

The growth of supermassive black holes (SMBHs) through merging has long been predicted but its detection remains elusive. However, a promising target has been discovered in the Seyfert-1 galaxy J1430+2303. If a binary system truly lies at the center of J1430+2303, the usual symmetry expected from pole-on views in active galactic nuclei (AGNs) responsible for the observed low ($\le$ 1\%) optical linear polarization in the continuum of these objects is expected to be broken. This should lead to higher-than-usual polarization degrees, together with time-dependent variations of the polarization signal. We used the specialized photopolarimeters RoboPol mounted on the 1.3m telescope at the Skinakas Observatory and the Alhambra Faint Object Spectrograph and Camera (ALFOSC) mounted on the 2.56m Nordic Optical Telescope (NOT) at the "Roque de los Muchachos" Observatory to measure the B-, V-, R-, and I-band polarization of J1430+2303. Observations were complemented using the FORS2 spectropolarimeter mounted on the VLT to acquire 3500 -- 8650 Angs polarized spectra. We compared our set of observations to Monte Carlo radiative-transfer predictions to look for the presence of a SMBH binary. The observed linear continuum polarization of J1430+2303 in the V and R bands is $\sim$ 0.4\% with an associated polarization angle of slightly larger than 0$^\circ$. We detected no significant changes in polarization or photometry between May, June, and July of 2022. In addition, there is no significant difference between the polarization of H$\alpha$ and the polarization of the continuum. A single SMBH at the center of an AGN model is able to reproduce the observed spectrum and polarization, while the binary hypothesis is rejected with a probability of $\sim$85\%.

GN-z11 is an unusually luminous high redshift galaxy which was recently observed to have strong nitrogen lines while at the same time lacking traditional signatures of AGN activity. These observations have been interpreted as a super-solar nitrogen abundance which is challenging to explain with standard stellar evolution and supernovae enrichment. We present simulations of four models of metal enriched supermassive stars after the zero age main sequence which produce super-solar nitrogen consistent with the observations of GN-z11. We then show that the most massive model ends its life in a violent explosion which results in even greater nitrogen pollution.

The process of accretion through circumstellar disks in young stellar objects is an integral part of star formation and the $H\alpha$ emission line is a prominent signature of accretion in low-mass stars. We present the detection and characterization of $H\alpha$ emission line sources in the central region of a distant, low-metallicity young stellar cluster - Dolidze 25 (at $\sim$ 4.5 kpc) - using medium-resolution optical spectra (4750-9350 \r{A} ) obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the VLT. We have identified 14 potential accreting sources within a rectangular region of (2$'$ x 1$'$) towards the center of the cluster based on the detection of strong and broad emissions in $H\alpha$ as well as the presence of other emission lines such as [OI] and $H\beta$. Based on their positions in both photometric color-magnitude and color-color diagrams, we have also confirmed that these objects belong to the pre-main sequence phase of star formation. Our results were compared with the disk and diskless members of the cluster previously identified by Guarcello et al. (2021) using near-IR colors, and all sources they had identified as disks were confirmed to be accreting based on the spectroscopic characteristics.

We present the H{\alpha} luminosity function (LF) derived from a large sample of Lyman break galaxies at z {\sim} 4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The H{\alpha} flux is derived from the offset between the continuum flux estimated from the best-fit spectral energy distribution, and the observed photometry in IRAC [3.6]. From these measurements, we build the H{\alpha} LF and study its evolution providing the best constraints of this property at high redshift, where spectroscopy of H{\alpha} is not yet available. Schechter parameterizations of the H{\alpha} LF show a decreasing evolution of {\Phi^\star} with redshift, increasing evolution in L{^\star}, and no significant evolution in the faint-end slope at high z. We find that star formation rates (SFRs) derived from H{\alpha} are higher than those derived from the rest-frame UV for low SFR galaxies but the opposite happens for the highest SFRs. This can be explained by lower mass galaxies (also lower SFR) having, on average, rising star formation histories (SFHs), while at the highest masses the SFHs may be declining. The SFR function is steeper, and because of the excess SFR(H{\alpha}) compared to SFR(UV) at low SFRs, the SFR density estimated from H{\alpha} is higher than the previous estimates based on UV luminosities.

The question of what ingredients characterize the quasi-steady state of fast neutrino-flavor conversion (FFC) is one of the long-standing riddles in neutrino oscillation. Addressing this issue is necessary for accurate modeling of neutrino transport in core-collapse supernova and binary neutron star merger. Recent numerical simulations of FFC have shown, however, that the quasi-steady state is sensitively dependent on boundary conditions in space, and the physical reason for the dependence is not clear at present. In this study, we provide a physical interpretation of this issue based on arguments with stability and conservation laws. The stability can be determined by the disappearance of ELN(electron neutrino-lepton number)-XLN(heavy-leptonic one) angular crossings, and we also highlight two conserved quantities characterizing the quasi-steady state of FFC: (1) lepton number conservation along each neutrino trajectory and (2) conservation law associated with angular moments, depending on boundary conditions, for each flavor of neutrinos. We demonstrate that neutrino distributions in quasi-steady states can be determined in an analytic way regardless of boundary conditions, which are in good agreement with numerical simulations. This study represents a major step forward a unified picture determining asymptotic states of FFCs.

Observations are beginning to constrain the history of the epoch of reionization (EoR). Modeling the reionization process is indispensable to interpret the observations, to infer the properties of ionizing sources, and to probe the various astrophysical processes from the observational data. Here we present an improved version of the semi-numerical simulation islandFAST, by incorporating inhomogeneous recombinations and a corresponding inhomogeneous ionizing background, and simulate the reionization process of neutral islands during the late EoR. We find that the islands are more fragmented in models with inhomogeneous recombinations than the case with a homogeneous recombination number. In order to investigate the effects of basic assumptions in the reionization modeling, we compare the results from islandFAST with those from 21cmFAST for the same assumptions on the ionizing photon sources and sinks, to find how the morphology of the ionization field and the reionization history depend on the different treatments of these two models. Such systematic bias should be noted when interpreting the upcoming observations.

The presence of differential reddening in the direction of Galactic globular clusters (GCs) has proven to be a serious limitation in the traditional colour-magnitude diagram (CMD) analysis. Here, we estimate local reddening variations in the direction of 56 Galactic GCs. To do that, we use the public catalogs derived as part of the Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters, which include photometry in the F275W, F336W, F438W, F606W, and F814W filters. We correct photometry for differential reddening finding that for 21 out of 56 GCs the adopted correction procedure significantly improves the CMDs. Moreover, we measure the reddening law in the direction of these clusters finding that $R_{V}$ exhibits a high level of variability within the Galaxy, ranging from $\sim2.0$ to $\sim4.0$. The updated values of $R_{V}$ have been used to improve the determination of local reddening variations and derive high-resolution reddening maps in the direction of the 21 highly-reddened targets within our sample. To compare the results of the different clusters, we compute the 68$^{\rm th}$ percentile of the differential-reddening distribution, $\sigma_{\Delta A_{\rm F814W}}$. This quantity ranges from 0.003 mag to 0.030 mag and exhibits a significant anti-correlation with the absolute module of the Galactic latitude and a strong correlation with the average reddening in the direction of each cluster. Therefore, highly-reddened GCs located in the proximity of the Galactic plane typically show higher differential-reddening variations across their field of view.

State-of-the-art radio observatories produce large amounts of data which can be used to study the properties of radio galaxies. However, with this rapid increase in data volume, it has become unrealistic to manually process all of the incoming data, which in turn led to the development of automated approaches for data processing tasks, such as morphological classification. Deep learning plays a crucial role in this automation process and it has been shown that convolutional neural networks (CNNs) can deliver good performance in the morphological classification of radio galaxies. This paper investigates two adaptations to the application of these CNNs for radio galaxy classification. The first adaptation consists of using principal component analysis (PCA) during preprocessing to align the galaxies' principal components with the axes of the coordinate system, which will normalize the orientation of the galaxies. This adaptation led to a significant improvement in the classification accuracy of the CNNs and decreased the average time required to train the models. The second adaptation consists of guiding the CNN to look for specific features within the samples in an attempt to utilize domain knowledge to improve the training process. It was found that this adaptation generally leads to a stabler training process and in certain instances reduced overfitting within the network, as well as the number of epochs required for training.

When dust far-infrared spectral energy distributions (SEDs) are fitted with a single modified black body (MBB), the optical depths tend to be underestimated. This is caused by temperature variations, and fits with several temperature components could lead to smaller errors. We want to quantify the performance of the standard model of a single MBB in comparison with some multi-component models. We are interested in both the accuracy and computational cost. We examine some cloud models relevant for interstellar medium studies. Synthetic spectra are fitted with a single MBB, a sum of several MBBs, and a sum of fixed spectral templates, but keeping the dust opacity spectral index fixed. When observations are used at their native resolution, the beam convolution becomes part of the fitting procedure. This increases the computational cost, but the analysis of large maps is still feasible with direct optimisation or even with Markov chain Monte Carlo methods. Compared to the single MBB fits, multi-component models can show significantly smaller systematic errors, at the cost of more statistical noise. The $\chi^2$ values of the fits are not a good indicator of the accuracy of the $\tau$ estimates, due to the potentially dominant role of the model errors. The single-MBB model also remains a valid alternative if combined with empirical corrections to reduce its bias. It is technically feasible to fit multi-component models to maps of millions of pixels. However, the SED model and the priors need to be selected carefully, and the model errors can only be estimated by comparing alternative models.

We found four series of harmonically related lines in IRC\,+10216 with the Yebes\,40m and IRAM\,30m telescopes. The first series corresponds to a molecule with a rotational constant, $B$, of 1448.5994$\pm$0.0013 MHz and a distortion constant, $D$, of 63.45$\pm$1.15 Hz and covers upper quantum numbers from $J_u$=11 up to 33 (B1449). The second series is fitted with $B$=1446.9380$\pm$0.0098 MHz and $D$=91$\pm$23 Hz and covers upper quantum numbers from $J_u$=11 up to 17 (B1447). The third series is fitted with $B$=598.7495$\pm$0.0011 MHz and D=6.13$\pm$0.43 Hz and covers quantum numbers from $J_u$=26 up to 41 (B599). Finally, the frequencies of the last series of lines can be reproduced with $B$=594.3176$\pm$0.0026 MHz and $D$=4.92$\pm$1.16 Hz (B594). The large values of $D$ point toward four metal-bearing carriers. After exploring all plausible candidates containing Na, Al, Mg, and other metals, our ab initio calculations indicate that the cations MgC$_4$H$^+$, MgC$_3$N$^+$, MgC$_6$H$^+$, and MgC$_5$N$^+$ must be the carriers of B1449, B1447, B599, and B594, respectively. These cations could be formed by the radiative association of Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N, respectively. We calculated the radiative association rate coefficient of Mg$^+$ with C$_4$H, C$_3$N, C$_6$H, and C$_5$N and incorporated them in our chemical model. The results confirm that the Mg-bearing cations can be formed through these radiative association reactions in the outer layers of IRC\,+10216. This is the first time that cationic metal-bearing species have been found in space. These results provide a new paradigm on the reactivity of ionized metals with abundant radicals and open the door for further characterization of similar species in metal-rich astrophysical environments.

There have been many efforts in the last three decades to embed the empirical MOND program into a robust theoretical framework. While many such theories can explain the profile of galactic rotation curves, they usually cannot explain the evolution 15 the primordial fluctuations and the formation of large-scale-structures in the Universe. The Aether Scalar Tensor (AeST) theory seems to have overcome this difficulty, thereby providing the first compelling example of an extension of general relativity able to successfully challenge the particle dark matter hypothesis. Here we study the phenomenology of this theory in the quasistatic weak-field regime and specifically for the idealised case of spherical isolated sources. We find the existence of three distinct gravitational regimes, that is, Newtonian, MOND and a third regime characterised by the presence of oscillations in the gravitational potential which do not exist in the traditional MOND paradigm. We identify the transition scales between these three regimes and discuss their dependence on the boundary conditions and other parameters in the theory. Aided by analytical and numerical solutions, we explore the dependence of these solutions on the theory parameters. Our results could help in searching for interesting observable phenomena at low redshift pertaining to galaxy dynamics as well as lensing observations, however, this may warrant proper N-body simulations that go beyond the idealised case of spherical isolated sources.

Koptelova et al. 2022 (K22) recently claimed a new quasar discovery at $z=7.46$. After careful consideration of the publicly-available data underlying K22's claim, we find that the observations were contaminated by a moving Solar System object, likely a main-belt asteroid. In the absence of the contaminated photometry, there is no evidence for the nearby, persistent WISE source being a high-redshift object; in fact, a detection of the source in DELS $z$-band rules out a redshift $z>7.3$. We present our findings as a cautionary tale of the dangers of passing asteroids for photometric selections.

A well-known paradigm about the origin of Galactic cosmic rays (CRs) is that these high-energy particles are accelerated in the process of diffusive shock acceleration (DSA) at collisionless shocks (at least up to the so-called "knee"energy of $10^{15}$ eV). Knowing the details of injection of electrons, protons and heavier nuclei into the DSA, their initial and the resulting spectrum, is extremely important in many "practical" applications of the CR astrophysics, e.g. in modelling of the gamma or synchrotron radio emission of astrophysical sources. In this contribution I we will give an overview of the DSA theory and the results of observations and kinetic Particle-In-Cell (PIC) simulations that support the basic theoretical concepts. PIC simulations of quasi-parallel collisionless shocks show that thermal and supra-thermal proton distribution functions at the shock can be represented by a single quasi-thermal distribution - the $\kappa$-distribution that is commonly observed in out-of-equilibrium space plasmas. Farther downstream, index $\kappa$ increases and the low-energy spectrum tends to Maxwell distribution. On the other hand, higher-energy particles continue through the acceleration process and the non-thermal particle spectrum takes a characteristic power-law form predicted by the linear DSA theory. In the end, I will show what modification of the spectra is expected in the non-linear DSA, when CR back-reaction to the shock is taken into account.

This study provides the results of simultaneous multicolor observations for the first Visorsat (STARLINK-1436) and the ordinary Starlink satellite, STARLINK-1113 in the $U$, $B$, $V$, $g'$, $r$, $i$, $R_{\rm C}$, $I_{\rm C}$, $z$, $J$, $H$, and $K_s$ bands to quantitatively investigate the extent to which Visorsat reduces its reflected light. Our results are as follows: (1) in most cases, Virorsat is fainter than STARLINK-1113, and the sunshade on Visorsat, therefore, contributes to the reduction of the reflected sunlight; (2) the magnitude at 550 km altitude (normalized magnitude) of both satellites often reaches the naked-eye limiting magnitude ($<$ 6.0); (3) from a blackbody radiation model of the reflected flux, the peak of the reflected components of both satellites is around the $z$ band; and (4) the albedo of the near infrared range is larger than that of the optical range. Under the assumption that Visorsat and STARLINK-1113 have the same reflectivity, we estimate the covering factor, $C_{\rm f}$, of the sunshade on Visorsat, using the blackbody radiation model: the covering factor ranges from $0.18 \leq C_{\rm f} \leq 0.92$. From the multivariable analysis of the solar phase angle (Sun-target-observer), the normalized magnitude, and the covering factor, the phase angle versus covering factor distribution presents a moderate anti-correlation between them, suggesting that the magnitudes of Visorsat depend not only on the phase angle but also on the orientation of the sunshade along our line of sight. However, the impact on astronomical observations from Visorsat-designed satellites remains serious. Thus, new countermeasures are necessary for the Starlink satellites to further reduce reflected sunlight.

The efficacy of coronal mass ejection (CME) observations as a key input to space weather forecasting is explored by comparing on and off Sun-Earth line observations from the ESA/NASA SOHO and NASA STEREO spacecraft. A comparison is made of CME catalogues based on L1 coronagraph imagery and off Sun-Earth line coronagraph and heliospheric imager (HI) observations, for the year 2011. Analysis reveals inconsistencies in the identification of a number of potentially Earth-directed CMEs. The catalogues reflect our ability to identify and characterise CMEs, so any discrepancies can impact our prediction of Earth-directed CMEs. We show that 15 CMEs, which were observed by STEREO, that had estimated directions compatible with Earth-directed events, had no identified halo/partial halo counterpart listed in the L1 coronagraph CME catalogue. In-situ data confirms that for 9 of these there was a consistent L1 Interplanetary CME (ICME). The number of such "discrepant" events is significant compared to the number of ICMEs recorded at L1 in 2011, stressing the need to address space weather monitoring capabilities, particularly with the inclusion of off Sun-Earth line observation. While the study provides evidence that some halo CMEs are simply not visible in near-Earth coronagraph imagery, there is evidence that some halo CMEs viewed from L1 are compromised by preceding CME remnants or the presence of multiple-CMEs. This underlines (1) the value of multiple vantage point CME observation, and (2) the benefit of off Sun-Earth line platform heliospheric imaging, and coronagraph imaging, for the efficient identification and tracking of Earth-directed events.

We show that a typical X-ray outburst light curve of Aql X-1 can be reproduced by accretion onto the neutron star in the frame of the disc instability model without invoking partial accretion or propeller effect. The knee and the subsequent sharp decay in the X-ray light curve can be generated naturally by taking into account the weak dependence of the disc aspect ratio, $h/r$, on the disc mass-flow rate, $\dot{M}_\mathrm{in}$, in the X-ray irradiation flux calculation. This $\dot{M}_\mathrm{in}$ dependence of $h/r$ only slightly modifies the irradiation temperature profile along the hot disc in comparison to that obtained with constant $h/r$. Nevertheless, this small difference has a significant cumulative effect on the hot disc radius leading to a much faster decrease in the size of the hot disc, and thereby to a sharper decay in the X-ray outburst light curve. The same model also produces the long-term evolution of the source consistently with its observed outburst recurrence times and typical light curves of Aql X-1. Our results imply that the source accretes matter from the disc in the quiescent state as well. We also estimate that the dipole moment of the source $\mu \lesssim 2 \times 10^{26}$ G cm$^3$.

Flagship near-future surveys targeting $10^8-10^9$ galaxies across cosmic time will soon reveal the processes of galaxy assembly in unprecedented resolution. This creates an immediate computational challenge on effective analyses of the full data-set. With simulation-based inference (SBI), it is possible to attain complex posterior distributions with the accuracy of traditional methods but with a $>10^4$ increase in speed. However, it comes with a major limitation. Standard SBI requires the simulated data to have identical characteristics to the observed data, which is often violated in astronomical surveys due to inhomogeneous coverage and/or fluctuating sky and telescope conditions. In this work, we present a complete SBI-based methodology, ``SBI$^{++}$,'' for treating out-of-distribution measurement errors and missing data. We show that out-of-distribution errors can be approximated by using standard SBI evaluations and that missing data can be marginalized over using SBI evaluations over nearby data realizations in the training set. In addition to the validation set, we apply SBI$^{++}$ to galaxies identified in extragalactic images acquired by the James Webb Space Telescope, and show that SBI$^{++}$ can infer photometric redshifts at least as accurately as traditional sampling methods and crucially, better than the original SBI algorithm using training data with a wide range of observational errors. SBI$^{++}$ retains the fast inference speed of $\sim$1 sec for objects in the observational training set distribution, and additionally permits parameter inference outside of the trained noise and data at $\sim$1 min per object. This expanded regime has broad implications for future applications to astronomical surveys.

In this article, it is shown that the $C_k$ and $LCm$ variables, recently introduced as an effective way to discriminate gamma and proton-induced showers in large wide-field gamma-ray observatories, can be generalised to be used in arrays of different detectors and variable fill factors. In particular, the $C_k$ profile discrimination capabilities are evaluated for scintillator and water Cherenkov detector arrays.

Over the last few years, there has been a large momentum to ensure that the third-generation era of gravitational wave detectors will find its realisation in the next decades, and numerous design studies have been ongoing for some time. Some of the main factors determining the cost of the Einstein Telescope lie in the length of the interferometer arms and its shape: L-shaped detectors versus a single triangular configuration. Both designs are further expected to include a xylophone configuration for improvement on both ends of the frequency bandwidth of the detector. We consider binary neutron star sources in our study, as examples of sources already observed with the current generation detectors and ones which hold most promise given the broader frequency band and higher sensitivity of the third-generation detectors. We estimate parameters of the sources, with different kinds of configurations of the Einstein Telescope detector, varying arm-lengths as well as shapes and alignments. Overall, we find little improvement with respect to changing the shape, or alignment. However, there are noticeable differences in the estimates of some parameters, including tidal deformability, when varying the arm-length of the detectors. In addition, we also study the effect of changing the laser power, and the lower limit of the frequency band in which we perform the analysis.

We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from the Cosmic Evolution Early Release Science Survey (CEERS) NIRCam imaging with photometric redshifts z_phot>8. We measure emission line redshifts of z=7.65 and 8.64 for two galaxies, and z=9.77(+0.37,-0.29) and 10.01(+0.14,-0.19) for two others via the detection of continuum breaks consistent with Lyman-alpha opacity from a mostly neutral intergalactic medium. The presence (absense) of strong breaks (strong emission lines) give high confidence that these two galaxies are at z>9.6, but the break-derived redshifts have large uncertainties given the low spectral resolution and relatively low signal-to-noise of the CEERS NIRSpec prism data. The two z~10 sources are relatively luminous (M_UV<-20), with blue continua (-2.3<beta<-1.9) and low dust attenuation (A_V=0.15(+0.3,-0.1)); and at least one of them has high stellar mass for a galaxy at that redshift (log(M_*/M_sol)=9.3(+0.2,-0.3)). Considered together with spectroscopic observations of other CEERS NIRCam-selected high-z galaxy candidates in the literature, we find a high rate of redshift confirmation and low rate of confirmed interlopers (8.3%). Ten out of 34 z>8 candidates with CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of emission lines in their spectra is consistent with redshifts z>9.6. We find that z>8 photometric redshifts are generally in agreement (within uncertainties) with the spectroscopic values. However, the photometric redshifts tend to be slightly overestimated (average Delta(z)=0.50+/-0.12), suggesting that current templates do not fully describe the spectra of very high-z sources. Overall, our results solidifies photometric evidence for a high space density of bright galaxies at z>8 compared to theoretical model predictions, and further disfavors an accelerated decline in the integrated UV luminosity density at z>8.

We analyze rest-frame ultraviolet to optical spectra of three $z\simeq7.47$ - $7.75$ galaxies whose Ly$\alpha$-emission lines were previously detected with Keck/MOSFIRE observations, using the JWST/NIRSpec observations from the Cosmic Evolution Early Release Science (CEERS) survey. From NIRSpec data, we confirm the systemic redshifts of these Ly$\alpha$ emitters, and emission-line ratio diagnostics indicate these galaxies were highly ionized and metal poor. We investigate Ly$\alpha$ line properties, including the line flux, velocity offset, and spatial extension. For the one galaxy where we have both NIRSpec and MOSFIRE measurements, we find a significant offset in their flux measurements ($\sim5\times$ greater in MOSFIRE) and a marginal difference in the velocity shifts. The simplest interpretation is that the Ly$\alpha$ emission is extended and not entirely encompassed by the NIRSpec slit. The cross-dispersion profiles in NIRSpec reveal that Ly$\alpha$ in one galaxy is significantly more extended than the non-resonant emission lines. We also compute the expected sizes of ionized bubbles that can be generated by the Ly$\alpha$ sources, discussing viable scenarios for the creation of sizable ionized bubbles ($>$1 physical Mpc). The source with the highest-ionization condition is possibly capable of ionizing its own bubble, while the other two do not appear to be capable of ionizing such a large region, requiring additional sources of ionizing photons. Therefore, the fact that we detect Ly$\alpha$ from these galaxies suggests diverse scenarios on escape of Ly$\alpha$ during the epoch of reionization. High spectral resolution spectra with JWST/NIRSpec will be extremely useful for constraining the physics of patchy reionization.

Majorons are (pseudo-)Nambu-Goldstone bosons associated with lepton number symmetry breaking due to the Majorana mass term of neutrinos introduced in the seesaw mechanism. They are good dark matter candidates since their lifetime is suppressed by the lepton number breaking scale. We update constraints and discuss future prospects on majoron dark matter in the singlet majoron models based on neutrino, gamma-ray, and cosmic-ray telescopes in the mass region of MeV--10 TeV.

Light primordial black holes (PBHs) with masses smaller than $10^9$ g ($10^{-24} M_\odot$) evaporate before the onset of Big-Bang nucleosynthesis, rendering their detection rather challenging. If efficiently produced, they may have dominated the universe energy density. We study how such an early matter-dominated era can be probed successfully using gravitational waves (GW) emitted by local and global cosmic strings. While previous studies showed that a matter era generates a single-step suppression of the GW spectrum, we instead find a "double-step" suppression for local-string GW whose spectral shape provides information on the duration of the matter era. The presence of the two steps in the GW spectrum originates from GW being produced through two events separated in time: loop formation and loop decay, taking place either before or after the matter era. The second step - called the "knee" - is a novel feature which is universal to any early matter-dominated era and is not only specific to PBHs. Detecting GWs from cosmic strings with LISA, ET, or BBO would set constraints on PBHs with masses between $10^6$ and $10^9$ g for local strings with tension $G\mu = 10^{-11}$, and PBHs masses between $10^4$ and $10^9$ g for global strings with symmetry-breaking scale $\eta = 10^{15}~\mathrm{GeV}$. Effects from the spin of PBHs are discussed.

When gravitational waves pass by a massive object on its way to the Earth, strong gravitational lensing effect will happen. Thus the GW signal will be amplified, deflected, and delayed in time. Through analysing the lensed GW waveform, physical properties of the lens can be inferred. On the other hand, neglecting lensing effects in the analysis of GW data may induce systematic errors in the estimating of source parameters. As a space-borne GW detector, TianQin will be launched in the 2030s. It is expected to detect dozens of MBHBs merger as far as z = 15, and thus will have high probability to detect at least one lensed event during the mission lifetime. In this article, we discuss the capability of TianQin to detect lensed MBHBs signals. Three lens models are considered in this work: the point mass model, the SIS model, and the NFW model. The sensitive frequency band for space-borne GW detectors is around milli-hertz, and the corresponding GW wavelength could be comparable to the lens gravitational length scale, which requires us to account for wave diffraction effects. In calculating lensed waveforms, we adopt the approximation of geometric optics at high frequencies to accelerate computation, while precisely evaluate the diffraction integral at low frequencies. Through a Fisher analysis, we analyse the accuracy to estimate the lens parameters. We find that the accuracy can reach to the level of 10^-3 for the mass of point mass and SIS lens, and to the level of 10^-5 for the density of NFW lens. We also assess the impact on the accurate of estimating the source parameters, and find that the improvement of the accuracy is dominated by the increasing of SNR.

We present analytical and numerical progress on black-hole binary spin precession at second post-Newtonian order using multi-timescale methods. In addition to the commonly used effective spin which acts as a constant of motion, we exploit the weighted spin difference and show that such reparametrization cures the coordinate singularity that affected the previous formulation for the case of equal-mass binaries. The dynamics on the precession timescale is written down in closed form in both coprecessing and inertial frames. Radiation-reaction can then be introduced in a quasi-adiabatic fashion such that, at least for binaries on quasi-circular orbits, gravitational inspirals reduce to solving a single ordinary differential equation. We provide a broad review of the resulting phenomenology and re-write the relevant physics in terms of the newly adopted parametrization. This includes the spin-orbit resonances, the up-down instability, spin propagation at past time infinity, and new precession estimators to be used in gravitational-wave astronomy. Our findings are implemented in version 2 of the public Python module PRECESSION. Performing a precession-averaged post-Newtonian evolution from/to arbitrarily large separation takes $\lesssim 0.1$ s on a single off-the-shelf processor. This allows for a wide variety of applications including propagating gravitational-wave posterior samples as well as population-synthesis predictions of astrophysical nature.

Domain wall networks are two-dimensional topological defects generally predicted in many beyond standard model physics. In this Letter, we propose to solve the domain wall problem with the first-order phase transition. We numerically study the phase transition dynamics, and for the first time show that the domain walls reached scaling regime can be diluted through the interaction with vacuum bubbles during the first-order phase transition. We find that the amplitude of the gravitational waves produced by the second-stage first-order phase transition is several orders higher than that from the domain walls evolution in the scaling regime. The scale of the first-order phase transition that dilute the domain walls can be probed through gravitational waves detection.