bluuebunny/crossref_metadata_2025 huggingface dataset:
The T Tauri star V410 Tau in the eyes of SPIRou and TESS
Authors: Finociety B , Donati J-F , Klein B , Zaire B , Lehmann L , Moutou C , Bouvier J , Alencar S H P , Yu L , Grankin K , Artigau É , Doyon R , Delfosse X , Fouqué P , Hébrard G , Jardine M , Kóspál Á , Ménard F ,   SLS consortium
Published: September 2021

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star V410 Tau based on data collected mostly with SPIRou, the near-infrared (NIR) spectropolarimeter recently installed at the Canada-France-Hawaii Telescope, as part of the SPIRou Legacy Survey large programme, and with TESS between October and December 2019. Using Zeeman–Doppler Imaging (ZDI), we obtained the first maps of photospheric brightness and large-scale magnetic field at the surface of this young star derived from NIR spectropolarimetric data. For the first time, ZDI is also simultaneously applied to high-resolution spectropolarimetric data and very-high-precision photometry. V410 Tau hosts both dark and bright surface features and magnetic regions similar to those previously imaged with ZDI from optical data, except for the absence of a prominent dark polar spot. The brightness distribution is significantly less contrasted than its optical equivalent, as expected from the difference in wavelength. The large-scale magnetic field (${\sim}410$ G), found to be mainly poloidal, features a dipole of ${\sim}390$ G, again compatible with previous studies at optical wavelengths. NIR data yield a surface differential rotation slightly weaker than that estimated in the optical at previous epochs. Finally, we measured the radial velocity of the star and filtered out the stellar activity jitter using both ZDI and Gaussian Process Regression down to a precision of ${\sim}0.15$ and 0.08 $\mathrm{km}\, \mathrm{s}^{-1}$ RMS, respectively, confirming the previously published upper limit on the mass of a potential close-in massive planet around V410 Tau.
A systematic bias in fitting the surface-density profiles of interstellar filaments
Authors: Whitworth A P , Priestley F D , Arzoumanian D
Published: September 2021

The surface-density profiles (SDPs) of dense filaments, in particular those traced by dust emission, appear to be well fit with Plummer profiles, i.e. Σ(b) = ΣB + ΣO{1 + [b/wO]2}[1 − p]/2. Here, $\, \Sigma _{{\rm B}}$ is the background surface density;  ΣB + ΣO is the surface density on the filament spine;  b is the impact parameter of the line-of-sight relative to the filament spine;  wO is the Plummer scale-length (which for fixed p is exactly proportional to the full width at half-maximum, $w_{{\rm O}}=\rm{\small fwhm}/2\lbrace 2^{2/[p-1]}-1\rbrace ^{1/2}$); and $\, p$ is the Plummer exponent (which reflects the slope of the SDP away from the spine). In order to improve signal to noise, it is standard practice to average the observed surface densities along a section of the filament, or even along its whole length, before fitting the profile. We show that, if filaments do indeed have intrinsic Plummer profiles with exponent pINTRINSIC, but there is a range of wO values along the length of the filament (and secondarily a range of ΣB values), the value of the Plummer exponent, pFIT, estimated by fitting the averaged profile, may be significantly less than pINTRINSIC. The decrease, Δp = pINTRINSIC − pFIT, increases monotonically (i) with increasing pINTRINSIC; (ii) with increasing range of wO values; and (iii) if (but only if) there is a finite range of wO values, with increasing range of ΣB values. For typical filament parameters, the decrease is insignificant if pINTRINSIC = 2 (0.05 ≲ Δp ≲ 0.10), but for pINTRINSIC = 3, it is larger (0.18 ≲ Δp ≲ 0.50), and for pINTRINSIC = 4, it is substantial (0.50 ≲ Δp ≲ 1.15). On its own, this effect is probably insufficient to support a value of pINTRINSIC much greater than pFIT ≃ 2, but it could be important in combination with other effects.
GW190521 formation via three-body encounters in young massive star clusters
Authors: Dall’Amico Marco , Mapelli Michela , Di Carlo Ugo N , Bouffanais Yann , Rastello Sara , Santoliquido Filippo , Ballone Alessandro , Arca Sedda Manuel
Published: September 2021

GW190521 is the most massive binary black hole (BBH) merger observed to date, and its primary component lies in the pair-instability (PI) mass gap. Here, we investigate the formation of GW190521-like systems via three-body encounters in young massive star clusters. We performed 2 × 105 simulations of binary-single interactions between a BBH and a massive $\ge {60}\,$M⊙ black hole (BH), including post-Newtonian terms up to the 2.5 order and a prescription for relativistic kicks. In our initial conditions, we take into account the possibility of forming BHs in the PI mass gap via stellar collisions. If we assume that first-generation BHs have low spins, $\sim {0.17}{{\ \rm per\ cent}}$ of all the simulated BBH mergers have component masses, effective and precessing spin, and remnant mass and spin inside the $90{{\ \rm per\ cent}}$ credible intervals of GW190521. Seven of these systems are first-generation exchanged binaries, while five are second-generation BBHs. We estimate a merger rate density $\mathcal {R}_{\rm GW190521}\sim {0.03}\,$Gpc$^{-3}\,$yr−1 for GW190521-like binaries formed via binary-single interactions in young star clusters. This rate is extremely sensitive to the spin distribution of first-generation BBHs. Stellar collisions, second-generation mergers and dynamical exchanges are the key ingredients to produce GW190521-like systems in young star clusters.
The angular momentum structure of CR-driven galactic outflows triggered by stream accretion
Authors: Peschken N , Hanasz M , Naab T , Wóltański D , Gawryszczak A
Published: September 2021

We investigate the impact of gas accretion in streams on the evolution of disc galaxies, using magnetohydrodynamic simulations including advection and anisotropic diffusion of cosmic rays (CRs) generated by supernovae as the only source of feedback. Stream accretion has been suggested as an important galaxy growth mechanism in cosmological simulations and we vary their orientation and angular momentum in idealized setups. We find that accretion streams trigger the formation of galactic rings and enhanced star formation. The star formation rates and consequently the CR-driven outflow rates are higher for low angular momentum accretion streams, which also result in more compact, lower angular momentum discs. The CR generated outflows show a characteristic structure. At low outflow velocities (<50 km s−1), the angular momentum distribution is similar to the disc and the gas is in a fountain flow. Gas at high outflow velocities (>200 km s−1), penetrating deep into the halo, has close to zero angular momentum, and originates from the centre of the galaxies. As the mass loading factors of the CR-driven outflows are of the order of unity and higher, we conclude that this process is important for the removal of low angular momentum gas from evolving disc galaxies and the transport of, potentially metal enriched, material from galactic centres far into the galactic haloes.
Testing extensions to ΛCDM on small scales with forthcoming cosmic shear surveys
Authors: Stafford Sam G , McCarthy Ian G , Kwan Juliana , Brown Shaun T , Font Andreea S , Robertson Andrew
Published: September 2021

We investigate the constraining power of forthcoming Stage-IV weak lensing surveys (Euclid, lsst, and NGRST) for extensions to the Lambda cold dark matter model on small scales, via their impact on the cosmic shear power spectrum. We use high-resolution cosmological simulations to calculate how warm dark matter (WDM), self-interacting dark matter (SIDM), and a running of the spectral index affect the non-linear matter power spectrum, P(k), as a function of scale and redshift. We evaluate the cosmological constraining power using synthetic weak lensing observations derived from these power spectra and that take into account the anticipated source densities, shape noise, and cosmic variance errors of upcoming surveys. We show that upcoming Stage-IV surveys will be able to place useful, independent constraints on both WDM models (ruling out models with a particle mass of ≲0.5 keV) and SIDM models (ruling out models with a velocity-independent cross-section of ≳10 cm2 g−1) through their effects on the small-scale cosmic shear power spectrum. Similarly, they will be able to strongly constrain cosmologies with a running spectral index. Finally, we explore the error associated with the cosmic shear cross-spectrum between tomographic bins, finding that it can be significantly affected by Poisson noise (the standard assumption is that the Poisson noise cancels between tomographic bins). We provide a new analytic form for the error on the cross-spectrum that accurately captures this effect.
Charting nearby stellar systems: the intensity of Galactic cosmic rays for a sample of solar-type stars
Authors: Rodgers-Lee D , Vidotto A A , Mesquita A L
Published: September 2021

Cosmic rays can penetrate planetary atmospheres driving the formation of prebiotic molecules, which are important for the origin of life. We calculate the Galactic cosmic ray fluxes in the habitable zone (HZ) of five nearby, well-studied solar-type stars and at the orbits of two known exoplanets. We model the propagation of Galactic cosmic rays through the stellar winds using a combined 1.5D stellar wind and 1D cosmic ray transport model. We find that the HZ of 61 Cyg A has comparable Galactic cosmic ray fluxes to present-day Earth values. For the other four systems (ϵ Eri, ϵ Ind, ξ Boo B, and π1 UMa), the fluxes are orders of magnitude smaller than Earth values. Thus, it is unlikely that any as-of-yet undetected Earth-like planets in their HZs would receive a higher radiation dose than is received on Earth. $\epsilon \,$Ind b, a Jupiter-like planet orbiting at ∼11 au, receives higher Galactic cosmic ray fluxes than Earth. We find the suppression of Galactic cosmic rays is influenced by whether diffusion or advection dominates at GeV energies and at distances where the wind has reached its’ terminal velocity. For advectively dominated winds (∼younger systems), varying the astrospheric size influences the suppression significantly. For diffusion-dominated systems (∼older systems), the astrospheric size, and therefore knowledge of the interstellar medium properties, are not very important. This reduces the Galactic cosmic ray flux uncertainties in the HZ for diffusion-dominated systems. Whether a system is advection- or diffusion-dominated can be determined from the stellar wind properties.
SDSS-IV MaNGA: the physical origin of off-galaxy H α blobs in the local Universe
Authors: Ji Xihan , Li Cheng , Yan Renbin , Mo Houjun , Lin Lihwai , Zou Hu , Lian Jianhui , Stark David V , Riffel Rogemar A , Pan Hsi-An , Bizyaev Dmitry , Bundy Kevin
Published: September 2021

H α blobs are off-galaxy emission-line regions with weak or no optical counterparts. They are mostly visible in H α line, appearing as concentrated blobs. Such unusual objects have been rarely observed and studied, and their physical origin is still unclear. We have identified 13 H α blobs in the public data of MaNGA survey, by visually inspecting both the optical images and the spatially resolved maps of H α line for ∼4600 galaxy systems. Among the 13 H α blobs, 2 were reported in previously MaNGA-based studies and 11 are newly discovered. This sample, though still small in size, is by far the largest sample with both deep imaging and integral field spectroscopy. Therefore, for the first time we are able to perform statistical studies to investigate the physical origin of H α blobs. We examine the physical properties of these H α blobs and their associated galaxies, including their morphology, environments, gas-phase metallicities, kinematics of ionized gas, and ionizing sources. We find that the H α blobs in our sample can be broadly divided into two groups. One is associated with interacting/merging galaxy systems, of which the ionization is dominated by shocks or diffuse ionized gas. It is likely that these H α blobs used to be part of their nearby galaxies, but were stripped away at some point due to tidal interactions. The other group is found in gas-rich systems, appearing as low-metallicity star-forming regions that are visually detached from the main galaxy. These H α blobs could be associated with faint discs, spiral arms, or dwarf galaxies.
On the equations of warped disc dynamics
Authors: Dullemond C P , Kimmig C N , Zanazzi J J
Published: September 2021

The 1D evolution equations for warped discs come in two flavours: For very viscous discs, the internal torque vector $\boldsymbol {G}$ is uniquely determined by the local conditions in the disc, and warps tend to damp out rapidly if they are not continuously driven. For very inviscid discs, on the other hand, $\boldsymbol {G}$ becomes a dynamic quantity, and a warp will propagate through the disc as a wave. The equations governing both regimes are usually treated separately. A unified set of equations was postulated recently by Martin et al., but not yet derived from the underlying physics. The standard method for deriving these equations is based on a perturbation series expansion, which is a powerful, but somewhat abstract technique. A more straightforward method is to employ the warped shearing box framework of Ogilvie & Latter, which so far has not yet been used to derive the equations for the wave-like regime. The goal of this paper is to analyse the warped disc equations in both regimes using the warped shearing box framework, to derive a unified set of equations, valid for small warps, and to discuss how our results can be interpreted in terms of the affine tilted-slab approach of Ogilvie.
Residual velocities of Small Magellanic Cloud star clusters
Authors: Piatti Andrés E
Published: September 2021

We analysed the largest Small Magellanic Cloud (SMC) cluster sample (32) with proper motions and radial velocity measurements, from which we obtained their space velocity components. By adopting as a reference, the recent best-fitting rotating disc of SMC star clusters as a function of the position angle, we computed their residual velocity vectors, and compared their magnitudes ($\Delta \, V$) with that of a cluster with residual velocity components equal to the velocity dispersions along the three independent SMC rotating disc axes of motion ($\Delta \, V$ = 60 km s−1). We found that clusters that belong to SMC tidally induced structures have $\Delta \, V\, \gt $ 50 km s−1, which suggests that space velocities of clusters in the process of escaping the rotating disc kinematics are measurably different. Studied clusters pertaining to a northern branch of the Magellanic Bridge, the main Magellanic Bridge, the Counter-Bridge, and the West Halo give support these findings. NGC 121, the oldest known SMC cluster, does not belong to any SMC tidal feature, and has $\Delta \, V$ = 64  km s−1, slightly above the boundary between bound and kinematically perturbed clusters.
Pisces VII: discovery of a possible satellite of Messier 33 in the DESI legacy imaging surveys
Authors: Martínez-Delgado David , Karim Noushin , Charles Emily J E , Boschin Walter , Monelli Matteo , Collins Michelle L M , Donatiello Giuseppe , Alfaro Emilio J
Published: September 2021

We report deep imaging observations with DOLoRes@TNG of an ultra-faint dwarf satellite candidate of the Triangulum galaxy (M33) found by visual inspection of the public imaging data release of the DESI Legacy Imaging Surveys. Pisces VII/Triangulum (Tri) III is found at a projected distance of $72\, {\rm kpc}$ from M33, and using the tip of the red giant branch method, we estimate a distance of $D=1.0^{+0.3}_{-0.2}\, {\rm Mpc}$, meaning the galaxy could either be an isolated ultra-faint or the second known satellite of M33. We estimate an absolute magnitude of MV = −6.1 ± 0.2 if Pisces VII/Tri II is at the distance of M33, or as bright as MV = −6.8 ± 0.2 if the galaxy is isolated. At the isolated distance, it has a physical half-light radius of $r_{\rm h}=131\pm 61\, {\rm pc}$ consistent with similarly faint galaxies around the Milky Way. As the tip of the red giant branch is sparsely populated, constraining a precision distance is not possible, but if Pisces VII/Tri III can be confirmed as a true satellite of M33, it is a significant finding. With only one potential satellite detected around M33 previously (Andromeda XXII/Tri I), it lacks a significant satellite population in stark contrast to the similarly massive Large Magellanic Cloud. The detection of more satellites in the outskirts of M33 could help to better illuminate if this discrepancy between expectation and observations is due to a poor understanding of the galaxy formation process, or if it is due to the low luminosity and surface brightness of the M33 satellite population which has thus far fallen below the detection limits of previous surveys. If it is truly isolated, it would be the faintest known field dwarf detected to date.
Large binocular telescope observations of new six compact star-forming galaxies with [Ne v] λ3426 Å emission
Authors: Izotov Y I , Thuan T X , Guseva N G
Published: September 2021

We report the discovery of [Ne v] λ3426 emission, in addition to He ii λ4686 emission, in six compact star-forming galaxies. These observations considerably increase the sample of eight such galaxies discovered earlier by our group. For four of the new galaxies, the optical observations are supplemented by near-infrared spectra. All galaxies, but one, have H ii regions that are dense, with electron number densities of ∼ 300–700 cm−3. They are all characterized by high H β equivalent widths EW(H β) ∼ 190–520 Å and high O32 = [O iii] λ5007/[O ii] λ3727 ratios of 10–30, indicating young starburst ages and the presence of high ionization radiation. All are low-metallicity objects with 12 + logO/H = 7.46–7.88. The spectra of all galaxies show a low-intensity broad component of the H α line and five of six objects show Wolf–Rayet features. Comparison with photoionization models shows that pure stellar ionization radiation from massive stars is not hard enough to produce such strong [Ne v] and He ii emission in our galaxies. The [Ne v] λ3426/He ii λ4686 flux ratio of ∼1.2 in J1222+3602 is consistent with some contribution of active galactic nucleus ionizing radiation. However, in the remaining five galaxies, this ratio is considerably lower, $\lesssim$ 0.4. The most plausible models are likely to be non-uniform in density, where He ii and [Ne v] lines are emitted in low-density channels made by outflows and illuminated by harder ionizing radiation from radiative shocks propagating through these channels, whereas [O iii] emission originates in denser regions exposed to softer stellar ionizing sources.
The effects of varying colour–luminosity relations on Type Ia supernova science
Authors: González-Gaitán S , de Jaeger T , Galbany L , Mourão A , Paulino-Afonso A , Filippenko A V
Published: September 2021

The success of Type Ia supernova (SN Ia) distance standardization for cosmology relies on a single global linear relationship between their peak luminosity and colour, the β parameter. However, there are several pieces of evidence and physical reasons to believe that this relation is not universal and may change within different subgroups, or even among individual objects. In this work, we allow β to vary among subpopulations with different observed properties in the cosmological fits. Although the inferred cosmological parameters are consistent with previous studies that assume a single colour–luminosity relation, we find that the SN data favour non-universal distributions of β when split according to SN colour and/or host-galaxy mass. For galaxy mass, we obtain a β-step relation in which low β values occur in more massive galaxies, a trend that can be explained by differing dust reddening laws for two types of environments. For colour, we find that bluer/redder SNe Ia are consistent with a lower/larger β. This trend is explained with β being a combination of a low intrinsic colour–luminosity relation dominant in bluer SNe and a higher extrinsic reddening relation dominant at redder colours. The host-galaxy mass-step correction always provides better distance calibration, regardless of the multiple β approaches, and we suggest that it may come from a difference in intrinsic colour–luminosity properties of SNe Ia in two types of environments. Additionally, we find that blue SNe in low-mass environments are better standard candles than the others.
A method to distinguish between micro- and macro-granular surfaces of small Solar system bodies
Authors: Bischoff D , Gundlach B , Blum J
Published: September 2021

The surface granularity of small Solar system bodies is diverse through the different types of planetary bodies and even for specific objects it is often not known in detail. One of the physical properties that strongly depends on the surface structure is the surface temperature. In highly porous media with large voids, radiation can efficiently transport heat, whereas more compact, micro-porous structures transport the heat primarily by conduction through the solid material. In this work, we investigate under which conditions a macro-porous surface can be distinguished from a micro-porous one by simply measuring the surface temperature. In our numerical simulations, we included circular and elliptical orbits with and without obliquity and varied the rotation period of the considered objects. We found that daily temperature cycles are rather insensitive to the specific surface granularity. However, the surface temperature at sunrise shows significant dependence on the material structure and this effect becomes even more pronounced when the solar intensity increases. By measuring the sunrise temperature as a function of insolation at noon, a differentiation between micro- and macro-granular surface structures is possible. In this paper, we provide a strategy on how remote sensing can be used to derive the surface structure of small Solar system bodies.
Minute-cadence Observations of the LAMOST Fields with the TMTS: I. Methodology of Detecting Short-period Variables and Results from the first-year Survey
Authors: Lin Jie , Wang Xiaofeng , Mo Jun , Xi Gaobo , Zhang Jicheng , Jiang Xiaojun , Shi Jianrong , Zhang Xiaobin , Zhang Xiaoming , Wei Zixuan , Ye Limeng , Wu Chengyuan , Yan Shengyu , Chen Zhihao , Li Wenxiong , Li Xue , Lin Weili , Lin Han , Sai Hanna , Xiang Danfeng , Zhang Xinghan
Published: September 2021

Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), located at Xinglong Station of NAOC, has a field of view up to 18 deg2. The TMTS has started to monitor the LAMOST sky areas since 2020, with the uninterrupted observations lasting for about 6 hours on average for each sky area and a cadence of about 1 minute. Here we introduce the data analysis and preliminary scientific results for the first-year observations, which covered 188 LAMOST plates (≈1970 deg2). These observations have generated over 4.9 million uninterrupted light curves, with at least 100 epochs for each of them. These light curves correspond to 4.26 million Gaia-DR2 sources, among which 285 thousand sources are found to have multi-epoch spectra from the LAMOST. By analysing these light curves with the Lomb-Scargle periodograms, we identify more than 3700 periodic variable star candidates with periods below ≈7.5 hours, primarily consisting of eclipsing binaries and δ Scuti stars. Those short-period binaries will provide important constraints on theories of binary evolution and possible sources for space gravitational wave experiments in the future. Moreover, we also identified 42 flare stars by searching rapidly-evolving signals in the light curves. The densely-sampled light curves from the TMTS allow us to better quantify the shapes and durations for these flares.
Preliminary clustering properties of the DESI BGS bright targets using DR9 Legacy Imaging Surveys
Authors: Zarrouk Pauline , Ruiz-Macias Omar , Cole Shaun , Norberg Peder , Baugh Carlton , Brooks David , Gaztañaga Enrique , Kitanidis Ellie , Kehoe Robert , Landriau Martin , Moustakas John , Prada Francisco , Tarlé Gregory
Published: September 2021

We characterize the selection cuts and clustering properties of a magnitude-limited sample of bright galaxies that is part of the Bright Galaxy Survey (BGS) of the Dark Energy Spectroscopic Instrument (DESI) using the ninth data release of the Legacy Imaging Surveys (DR9). We describe changes in the DR9 selection compared to the DR8 one and we also compare the DR9 selection in three distinct regions: BASS/MzLS in the north Galactic Cap (NGC), DECaLS in the NGC, and DECaLS in the south Galactic Cap (SGC). We investigate the systematics associated with the selection and assess its completeness by matching the BGS targets with the Galaxy and Mass Assembly (GAMA) survey. We measure the angular clustering for the overall bright sample (rmag ≤ 19.5) and as function of apparent magnitude and colour. This enables to determine the clustering strength r0 and slope γ by fitting a power-law model that can be used to generate accurate mock catalogues for this tracer. We use a counts-in-cells technique to explore higher order statistics and cross-correlations with external spectroscopic data sets in order to check the evolution of the clustering with redshift and the redshift distribution of the BGS targets using clustering redshifts. While this work validates the properties of the BGS bright targets, the final target selection pipeline and clustering properties of the entire DESI BGS will be fully characterized and validated with the spectroscopic data of Survey Validation.
The high-redshift tail of stellar reionization in LCDM is beyond the reach of the low-ℓ CMB
Authors: Wu Xiaohan , McQuinn Matthew , Eisenstein Daniel , Iršič Vid
Published: September 2021

The first generation (Pop-III) stars can ionize 1–10 per cent of the universe by z = 15, when the metal-enriched (Pop-II) stars may contribute negligibly to the ionization. This low ionization tail might leave detectable imprints on the large-scale CMB E-mode polarization. However, we show that physical models for reionization are unlikely to be sufficiently extended to detect any parameter beyond the total optical depth through reionization. This result is driven in part by the total optical depth inferred by Planck, indicating a reionization midpoint around z = 8, which in combination with the requirement that reionization completes by z ≈ 5.5 limits the amplitude of an extended tail. To demonstrate this, we perform semi-analytic calculations of reionization including Pop-III star formation in minihalos with Lyman-Werner feedback. We find that standard Pop-III models need to produce very extended reionization at z > 15 to be distinguishable at 2-σ from Pop-II-only models, assuming a cosmic variance-limited measurement of the low-ℓ EE power spectrum. However, we show that unless there is a late-time quenching mechanism such as from strong X-ray feedback or some other extreme Pop-III scenario, structure formation makes it quite challenging to produce high enough Thomson scattering optical depth from z > 15, τ(z > 15), and still be consistent with other observational constraints on reionization.
Exploring black hole scaling relations via the ensemble variability of active galactic nuclei
Authors: Georgakakis A , Papadakis I , Paolillo M
Published: September 2021

An empirical model is presented that links, for the first time, the demographics of active galactic nuclei (AGN) to their ensemble X-ray variability properties. Observations on the incidence of AGN in galaxies are combined with (i) models of the power spectrum density (PSD) of the flux variations of AGN and (ii) parametrizations of the black hole mass versus stellar mass scaling relation to predict the mean excess variance of active black hole populations in cosmological volumes. We show that the comparison of the model with observational measurements of the ensemble excess variance as a function of X-ray luminosity provides a handle on both the PSD models and the black hole mass versus stellar mass relation. We find strong evidence against a PSD model that is described by a broken power law and a constant overall normalization. Instead, our analysis indicates that the amplitude of the PSD depends on the physical properties of the accretion events, such as the Eddington ratio and/or the black hole mass. We also find that current observational measurements of the ensemble excess variance are consistent with the black hole mass versus stellar mass relation of local spheroids based on dynamically determined black hole masses. We also discuss future prospects of the proposed approach to jointly constrain the PSD of AGN and the black hole mass versus stellar mass relation as a function of redshift.
Impact of relativistic jets on the star formation rate: a turbulence-regulated framework
Authors: Mandal Ankush , Mukherjee Dipanjan , Federrath Christoph , Nesvadba Nicole P H , Bicknell Geoffrey V , Wagner Alexander Y , Meenakshi Moun
Published: September 2021

We apply a turbulence-regulated model of star formation to calculate the star formation rate (SFR) of dense star-forming clouds in simulations of jet–interstellar medium (ISM) interactions. The method isolates individual clumps and accounts for the impact of virial parameter and Mach number of the clumps on the star formation activity. This improves upon other estimates of the SFR in simulations of jet–ISM interactions, which are often solely based on local gas density, neglecting the impact of turbulence. We apply this framework to the results of a suite of jet–ISM interaction simulations to study how the jet regulates the SFR both globally and on the scale of individual star-forming clouds. We find that the jet strongly affects the multiphase ISM in the galaxy, inducing turbulence and increasing the velocity dispersion within the clouds. This causes a global reduction in the SFR compared to a simulation without a jet. The shocks driven into clouds by the jet also compress the gas to higher densities, resulting in local enhancements of the SFR. However, the velocity dispersion in such clouds is also comparably high, which results in a lower SFR than would be observed in galaxies with similar gas mass surface densities and without powerful radio jets. We thus show that both local negative and positive jet feedback can occur in a single system during a single jet event, and that the SFR in the ISM varies in a complicated manner that depends on the strength of the jet–ISM coupling and the jet break-out time-scale.
Gas-phase formation of cationic fullerene/9-aminoanthracene clusters: an indicator for interstellar dust growth
Authors: Hu Xiaoyi , Zhang Deping , Zhang Congcong , Yang Yuanyuan , Chen Yang , Zhen Junfeng , Qin Liping
Published: September 2021

Growth of clusters by adduction of monomers – as the first step in dust particle growth – is an area of much interest in astronomy. We focus on the fullerene/9-aminoanthracene cluster species, to illustrate the competition between the van der Waals bonding growth and the covalent bonding growth model versus the charge transfer model in the large cluster formation process. The experimental results show that fullerene-fragment (C56 and C58)/9-aminoanthracene cluster cations, e.g. [(C14H11N)nC56]+ and [(C14H11N)nC58]+, n = [1,7], are efficiently formed, while C$_{60}^+$ is insensitive to the cluster’s formation. With laser irradiation, all the fullerene/9-aminoanthracene clusters dissociate into 9-aminoanthracene and fullerene cations. The mechanisms for the reactions of fullerene cations and 9-aminoanthracene were investigated by theoretical calculations, under the assumption that the molecular geometries found for the formed complexes correspond to the global energy minima: the absence of C$_{60}^+$ clusters is mainly due to the charge transfer channel’s competition; [(C14H11N)C58]+ has three types of isomers, with van der Waals or covalent bonds, mainly depending on the reaction sites of fullerene cations. Importantly, in the size grown process, for the fullerene/9-aminoanthracene cluster there exists a geometry configuration conversion between the van der Waals and covalent bonding modes. The largest fullerene/9-aminoanthracene clusters, e.g. [(C14H11N)7C58]+ (240 atoms, ∼4 nm in size), are likely in a multishelled geometry, i.e. seven 9-aminoanthracene molecules surrounding fullerene cations in two layers, which can directly build the relationship between molecular clusters and carbonaceous grains. Nitrogen matters! The specific side chains (e.g. –NH2) play an important role in the growth of interstellar dust.
Molecular gas along the old radio jets of the cluster-central type 2 quasar IRAS 09104+4109
Authors: O’Sullivan Ewan , Combes Françoise , Babul Arif , Chapman Scott , Phadke Kedar A , Schellenberger Gerrit , Salomé Philippe
Published: September 2021

We present Northern Extended Millimeter Array (NOEMA) CO(2–1) maps of the z = 0.4418 cluster-central quasi-stellar object (QSO) IRAS 09104+4109, which trace ∼4.5 × 1010 M⊙ of molecular gas in and around the galaxy. As in many low-redshift cool-core clusters, the molecular gas is located in a series of clumps extending along the old radio jets and lobes. It has a relatively low velocity dispersion [336$^{+39}_{-35}$ km s−1 full width at half-maximum (FWHM)] and shows no velocity gradients indicative of outflow or infall. Roughly half the gas is located in a central clump on the north-east side of the galaxy, overlapping a bright ionized gas filament and a spur of excess X-ray emission, suggesting that this is a location of rapid cooling. The molecular gas is unusually extended, out to ∼55 kpc radius, comparable to the scale of the filamentary nebula in the Perseus cluster, despite the much higher redshift of this system. The extent falls within the thermal instability radius of the intracluster medium (ICM), with tcool/$t_{\rm ff} \lt 25$ and tcool/$t_{\rm eddy} \sim 1$ within ∼70 kpc. Continuum measurements at 159.9 GHz from NOEMA and 850 $\mu$m from the James Clerk Maxwell Telescope (JCMT) Submillimeter Common-User Bolometer Array 2 (SCUBA-2) show excess far-infrared emission, which we interpret as free–free emission arising from the ongoing starburst. These observations suggest that ICM cooling is not strongly affected by the buried QSO, and that cooling from the ICM can build gas reservoirs sufficient to fuel quasar-mode activity and drive the reorientation of the central active galactic nuclei (AGN).
Non-radial modes in classical Cepheids: what to look for in spectroscopy?
Authors: Netzel H , Kolenberg K
Published: September 2021

Recent photometric observations of first-overtone classical Cepheids and RR Lyrae stars have led to the discovery of additional frequencies showing a characteristic period ratio of 0.60–0.65 with the main pulsation mode. In a promising model proposed by Dziembowski (2016), these signals are suggested to be due to the excitation of non-radial modes with degrees 7, 8, and 9 (Cepheids) or 8 and 9 (RR Lyrae). Such modes usually have low amplitudes in photometric data. Spectroscopic time series offer an unexplored and promising way forward. We simulated time series of synthetic line profiles for a representative first-overtone classical Cepheid model and added a low-amplitude non-radial mode. We studied sets of spectra with dense sampling and without noise, so-called ’perfect’ cases, as well as more realistic samplings and signal-to-noise levels. Besides the first-overtone mode and the non-radial mode, also the harmonics of both modes and combination signals were often detected, but a sufficiently high sampling and signal-to-noise ratio prove essential. The amplitudes of the non-radial mode and its harmonic depend on the azimuthal order m. The inclination is also an important factor determining the detectability of the non-radial mode and/or its harmonic. We compared the results obtained for the predicted high degrees with those for lower-degree modes. Finally, we studied the sampling requirements for detecting the non-radial mode. Our findings can be used to plan a spectroscopic observing campaign tailored to uncover the nature of these mysterious modes.
Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background search
Authors: Chen S , Caballero R N , Guo Y J , Chalumeau A , Liu K , Shaifullah G , Lee K J , Babak S , Desvignes G , Parthasarathy A , Hu H , van der Wateren E , Antoniadis J , Bak Nielsen A-S , Bassa C G , Berthereau A , Burgay M , Champion D J , Cognard I , Falxa M , Ferdman R D , Freire P C C , Gair J R , Graikou E , Guillemot L , Jang J , Janssen G H , Karuppusamy R , Keith M J , Kramer M , Liu X J , Lyne A G , Main R A , McKee J W , Mickaliger M B , Perera B B P , Perrodin D , Petiteau A , Porayko N K , Possenti A , Samajdar A , Sanidas S A , Sesana A , Speri L , Stappers B W , Theureau G , Tiburzi C , Vecchio A , Verbiest J P W , Wang J , Wang L , Xu H
Published: September 2021

We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 yr. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, ENTERPRISE, and TEMPONEST+FORTYTWO, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power law with $A = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95 per cent credible regions). Fixing the spectral index to γ = 13/3 as expected from the GWB by circular, inspiralling supermassive black hole binaries results in an amplitude of $A =2.95_{-0.72}^{+0.89} \times 10^{-15}$. We implement three different models, BAYESEPHEM, LINIMOSS, and EPHEMGP, to address possible Solar system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension.
NGC 6124: a young open cluster with anomalous- and fast-rotating giant stars
Authors: Holanda N , Drake N A , Corradi W J B , Ferreira F A , Maia F , Magrini L , da Silva J R P , Pereira C B
Published: September 2021

We present the results of a chemical analysis of fast and anomalous rotator giants members of the young open cluster NGC 6124. For this purpose, we carried out abundances of the mixing sensitive species such as Li, C, N, Na, and 12C/13C isotopic ratio, as well as other chemical species for a sample of four giants among the seven observed ones. This study is based on standard spectral analysis technique using high-resolution spectroscopic data. We also performed an investigation of the rotational velocity ($v\, \sin \, i$) once this sample exhibits abnormal values – giant stars commonly present rotational velocities of few km s−1. In parallel, we have performed a membership study, making use of the third data release from ESA Gaia mission. Based on these data, we estimated a distance of d = 630 pc and an age of 178 Myr through isochrone fitting. After that procedure, we matched all the information raised and investigated the evolutionary stages and thermohaline mixing model through of spectroscopic Teff and $\log \, g$ and mixing tracers, such as 12C/13C and Na, of the studied stars. We derived a low mean metallicity of [Fe/H] = −0.13 ± 0.05 and a modest enhancement of the elements created by the s-process, such as Y, Zr, La, Ce, and Nd, which is in agreement with what has already been reported in the literature for young clusters. The giants analysed have homogeneous abundances, except for lithium abundance [$\log \, \epsilon$(Li)NLTE = 1.08 ± 0.42] and this may be associated with a combination of mechanisms that act increasing or decreasing lithium abundances in stellar atmospheres.
Gravitational fragmentation of extremely metal-poor circumstellar discs
Authors: Shima Kazuhiro , Hosokawa Takashi
Published: September 2021

We study the gravitational fragmentation of circumstellar discs accreting extremely metal-poor ($Z \le 10^{-3}\, \mathrm{Z}_{\odot }$) gas, performing a suite of 3D hydrodynamic simulations using the adaptive mesh refinement code enzo. We systematically follow the long-term evolution for 2 × 103 yr after the first protostar’s birth, for the cases of Z = 0, 10−5, 10−4, and $10^{-3}\, \mathrm{Z}_{\odot }$. We show that evolution of number of self-gravitating clumps qualitatively changes with Z. Vigorous fragmentation induced by dust cooling occurs in the metal-poor cases, temporarily providing ∼10 self-gravitating clumps at Z = 10−5 and $10^{-4}\, \mathrm{Z}_{\odot }$. However, we also show that the fragmentation is a very sporadic process; after an early episode of the fragmentation, the number of clumps continuously decreases as they merge away in these cases. The vigorous fragmentation tends to occur later with the higher Z, reflecting that the dust-induced fragmentation is most efficient at the lower density. At $Z = 10^{-3}\, \mathrm{Z}_{\odot }$, as a result, the clump number stays smallest until the disc fragmentation starts in a late stage. We also show that the clump mass distribution depends on the metallicity. A single or binary clump substantially more massive than the others appear only at $Z = 10^{-3}\, \mathrm{Z}_{\odot }$, whereas they are more evenly distributed in mass at the lower metallicities. We suggest that the disc fragmentation should provide the stellar multiple systems, but their properties drastically change with a tiny amount of metals.
Fractal dimension of optical cirrus in Stripe82
Authors: Marchuk Alexander A , Smirnov Anton A , Mosenkov Aleksandr V , Il’in Vladimir B , Gontcharov George A , Savchenko Sergey S , Román Javier
Published: September 2021

The geometric characteristics of dust clouds provide important information on the physical processes that structure such clouds. One of such characteristics is the 2D fractal dimension D of a cloud projected on to the sky plane. In previous studies, which were mostly based on infrared (IR) data, the fractal dimension of individual clouds was found to be in a range from 1.1 to 1.7 with a preferred value of 1.2–1.4. In this work, we use data from Stripe82 of the Sloan Digital Sky Survey to measure the fractal dimension of the cirrus clouds. This is done here for the first time for optical data with significantly better resolution as compared to IR data. To determine the fractal dimension, the perimeter-area method is employed. We also consider IR (IRAS and Herschel) counterparts of the corresponding optical fields to compare the results between the optical and IR. We find that the averaged fractal dimension across all clouds in the optical is $\langle D \rangle =1.69^{+0.05}_{-0.05}$ which is significantly larger than the fractal dimension of its IR counterparts $\langle D\rangle =1.38^{+0.07}_{-0.06}$. We examine several reasons for this discrepancy (choice of masking and minimal contour level, image and angular resolution, etc.) and find that for approximately half of our fields the different angular resolution (point spread function) of the optical and IR data can explain the difference between the corresponding fractal dimensions. For the other half of the fields, the fractal dimensions of the IR and visual data remain inconsistent, which can be associated with physical properties of the clouds, but further physical simulations are required to prove it.
Testing the consistency of dust laws in SN Ia host galaxies: a BayeSN examination of Foundation DR1
Authors: Thorp Stephen , Mandel Kaisey S , Jones David O , Ward Sam M , Narayan Gautham
Published: September 2021

We apply BayeSN, our new hierarchical Bayesian model for the SEDs of Type Ia supernovae (SNe Ia), to analyse the griz light curves of 157 nearby SNe Ia (0.015 < z < 0.08) from the public Foundation Supernova Survey data set. We train a new version of BayeSN, continuous from 0.35 to 0.95 μm, which we use to model the properties of SNe Ia in the rest-frame z-band, study the properties of dust in their host galaxies, and construct a Hubble diagram of SN Ia distances determined from full griz light curves. Our griz Hubble diagram has a low total RMS of 0.13 mag using BayeSN, compared to 0.16 mag using SALT2. Additionally, we test the consistency of the dust law RV between low- and high-mass host galaxies by using our model to fit the full time- and wavelength-dependent SEDs of SNe Ia up to moderate reddening (peak apparent B − V ≲ 0.3). Splitting the population at the median host mass, we find RV = 2.84 ± 0.31 in low-mass hosts, and RV = 2.58 ± 0.23 in high-mass hosts, both consistent with the global value of RV = 2.61 ± 0.21 that we estimate for the full sample. For all choices of mass split we consider, RV is consistent across the step within ≲ 1.2σ. Modelling population distributions of dust laws in low- and high-mass hosts, we find that both subsamples are highly consistent with the full sample’s population mean μ(RV) = 2.70 ± 0.25 with a 95 per cent upper bound on the population σ(RV) < 0.61. The RV population means are consistent within ≲ 1.2σ. We find that simultaneous fitting of host-mass-dependent dust properties within our hierarchical model does not account for the conventional mass step.
Ultraluminous X-ray sources in seven edge-on spiral galaxies
Authors: Dage Kristen C , Vowell Noah , Thygesen Erica , Bahramian Arash , Haggard Daryl , Kovlakas Konstantinos , Kundu Arunav , Maccarone Thomas J , Strader Jay , Urquhart Ryan , Zepf Stephen E
Published: September 2021

We investigate a sample of seven edge-on spiral galaxies using Chandra observations. Edge-on spiral galaxies allow us to clearly separate source associated with their star-forming regions versus the outer edges of the system, offering a clear advantage over other systems. We uncover a number of X-ray point sources across these galaxies, and after eliminating contaminating foreground and background sources, we identify 12 candidate ultraluminous X-ray sources (ULXs). All of these sources are projected on to the central regions, implying that the majority of ULXs in this sample of spiral galaxies are disc/bulge, and thus not halo sources. This also includes two transient ULXs, which may be long-duration transients and low-mass X-ray binaries. This finding illustrates the need for further studies of transient ULXs.