Models Of Star Formation Research Articles

Interstellar Planetesimals: Potential Seeds for Planet Formation?

Abstract We investigate the trapping of interstellar objects during the early stages of star and planet formation. Our results show a very wide range of possible values that will be narrowed down as the population of interstellar objects becomes better characterized. When assuming a background number density of 2 · 1015 pc−3 (based on 1I’s detection), a velocity dispersion of 30 km s−1, and an equilibrium size distribution, the number of interstellar objects captured by a molecular cloud and expected to be incorporated to each protoplanetary disk during its formation is O(109) (50 cm–5 m), O(105) (5–50 m), O(102) (50–500 m), O(10−2) (500 m–5 km). After the disk has formed, the number of interstellar objects it can capture from the ISM during its lifetime is 6 · 1011 (50 cm–5 m), 2 · 108 (5–50 m), 6 · 104 (50–500 m), 20 (500 m–5 km); in an open cluster where 1% of stars have undergone planet formation, these values increase by a factor of O(102–103). These trapped interstellar objects might be large enough to rapidly grow into larger planetesimals via the direct accretion of the subcm-sized dust grains in the protoplanetary disk before they drift in due to gas drag, helping overcome the meter-size barrier, acting as “seeds” for planet formation. They should be considered in future star and planet formation models, as well as in the potential spread of biological material across the Galaxy.

Dynamically regulated star formation in the strongly interacting Taffy galaxies

The Taffy system stands out as one of the strongest gas-rich galaxy mergers with little star formation (SF) activity. We study the causes of this SF inefficiency by observing with the IRAM 30m telescope the line emission of several species in 6 positions. We report clear detections of tracers of bulk (12CO and 13CO) and dense (HCN and HCO+) molecular gas in all regions, as well as evidence for shocks (SiO J=2–1) over the intergalactic bridge. Our observations not only confirm the SF inefficiency of the bulk gas, but they also show that the SF efficiency of the dense gas phase is abnormally low too (∼1 dex below ULIRGs). The dense gas fraction (∝ HCN/CO) only shows small variations across the entire system, with a typical value of 4%. Although this fraction is somewhat low compared to other interacting/merging systems, it is similar to the values measured in the disk of nearby, normal star-forming galaxies. Finally, we use the outstanding properties of the Taffy system to place constraints on some of the turbulence-regulated SF models from the literature.

Populations of Ultraluminous X-ray Sources in Galaxies: Origin and Evolution

A model of the population of ultraluminous X-ray sources (ULXs) in binary systems with black hole (BH) accretors is constructed by hybrid population synthesis and is compared with the model of the population of ULXs with magnetized neutron stars (NSs) that can be observed as pulsating ULXs (Kuranov et al. 2020). A model of the formation of BHs whereby their mass is determined by the mass of the CO core immediately before its collapse ( $$M_{\mathrm{CO}}$$ ) and ‘‘delayed’’ and ‘‘rapid’’ collapse models (Fryer et al. 2012) are considered. The possible transiency of ULXs due to accretion disk instability is taken into account. The parameters and evolution of ULXs in galaxies with a constant star formation rate (SFR) and in those with an old stellar population after an instantaneous star formation burst are computed. The maximum number of ULXs with BHs ( $${\sim}10$$ ) is reached in galaxies with a stationary $$SFR=10M_{\odot}$$ yr $${}^{-1}$$ $${\sim}1$$ Gyr after the beginning of star formation. ULXs observed after the end of star formation are close binary systems in which BHs and/or NSs formed before the end of star formation, while long-lived donors with a mass $${\sim}M_{\odot}$$ continue to overflow their Roche lobes after its end or have filled their Roche lobes even later. Several Gyr after the end of star formation the number of ULXs in galaxies with a mass $$M_{G}=10^{10}M_{\odot}$$ is no more than 0.1, most of them are ULXs with NSs. Persistent sources with a Roche-lobe-overflowing optical star dominate in ULXs with NSs, irrespective of the adopted star formation model. The transient sources are an order of magnitude fewer. The ULXs accreting from the stellar wind of the optical component are an order of magnitude fewer than the sources with accretion via Roche lobe overflow.

A low-frequency pilot survey of southern H ii regions in the vela constellation

ABSTRACT Atomic ionized regions with strong continuum emission are often associated with regions of high-mass star formation and low-frequency (<2 GHz) observations of these regions are needed to help build star formation models. The region toward the Vela Supernova Remnant is particularly interesting as it is a complex structure of recent supernova explosions and molecular clouds containing a number of H ii regions that are not well characterized. We searched publicly available catalogues for H ii regions, both candidate and identified, which also have low-frequency emission. In the area of ∼400 square degrees toward the Vela Supernova remnant, we found 10 such H ii regions, some of which have multiple components in catalogues. In this work we use data from the Australian Square Kilometre Array Pathfinder and previously unpublished data from the Murchison Widefield Array and the Australian Telescope Compact Array to analyse these sources. The high-mass star forming region RCW 38, with observations specifically targeted on the source, is used as a pilot study to demonstrate how low-frequency, wide-field continuum observations can identify and study H ii regions in our Galaxy. For the nine other H ii regions, we discuss their properties; including information about which clouds are interacting, their ages, whether they are dominated by infrared or optical H α lines, distances, ionizing photon flux, and upper limits on the infrared luminosity. In future work, these nine regions will be analysed in more detail, similar to the result for RCW 38 presented here.

GASP XXXV: Characteristics of the Diffuse Ionised Gas in Gas-stripped Galaxies

Abstract Diffuse ionized gas (DIG) is an important component of the interstellar medium that can provide insights into the different physical processes affecting the gas in galaxies. We utilize optical IFU observations of 71 gas-stripped and control galaxies from the Gas Stripping Phenomena in galaxies (GASP) survey, to analyze the gas properties of dense ionized gas and DIG, such as metallicity, ionization parameter log(q), and the difference between the measured log[O i]/Hα and the value predicted by star-forming models given the measured log[Oiii]/Hβ (Δ log[O i]/Hα). We compare these properties at different spatial scales, among galaxies at different gas-stripping stages, and between disks and tails of the stripped galaxies. The metallicity is similar between the dense gas and DIG at a given galactocentric radius. The log(q) is lower for DIG compared to dense gas. The median values of log(q) correlate best with stellar mass and the most massive galaxies show an increase in log(q) toward their galactic centers. The DIG clearly shows higher Δ log[O i]/Hα values compared to the dense gas, with much of the spaxels having LIER/LINER-like emission. The DIG regions in the tails of highly stripped galaxies show the highest Δ log[O i]/Hα, exhibit high values of log(q), and extend to large projected distances from star-forming areas (up to 10 kpc). We conclude that the DIG in the tails is at least partly ionized by a process other than star formation, probably by mixing, shocks, and accretion of inter-cluster and interstellar medium gas.

The challenge of simulating the star cluster population of dwarf galaxies with resolved interstellar medium

ABSTRACT We present results on the star cluster properties from a series of high resolution smoothed particles hydrodynamics (SPH) simulations of isolated dwarf galaxies as part of the griffin project. The simulations at sub-parsec spatial resolution and a minimum particle mass of 4 M⊙ incorporate non-equilibrium heating, cooling, and chemistry processes, and realize individual massive stars. The simulations follow feedback channels of massive stars that include the interstellar-radiation field variable in space and time, the radiation input by photo-ionization and supernova explosions. Varying the star formation efficiency per free-fall time in the range ϵff = 0.2–50${{\ \rm per\ cent}}$ neither changes the star formation rates nor the outflow rates. While the environmental densities at star formation change significantly with ϵff, the ambient densities of supernovae are independent of ϵff indicating a decoupling of the two processes. At low ϵff, gas is allowed to collapse more before star formation, resulting in more massive, and increasingly more bound star clusters are formed, which are typically not destroyed. With increasing ϵff, there is a trend for shallower cluster mass functions and the cluster formation efficiency Γ for young bound clusters decreases from $50 {{\ \rm per\ cent}}$ to $\sim 1 {{\ \rm per\ cent}}$ showing evidence for cluster disruption. However, none of our simulations form low mass (<103 M⊙) clusters with structural properties in perfect agreement with observations. Traditional star formation models used in galaxy formation simulations based on local free-fall times might therefore be unable to capture star cluster properties without significant fine tuning.

Testing Models of Triggered Star Formation with Young Stellar Objects in Cepheus OB4

Abstract OB associations are home to newly formed massive stars, whose turbulent winds and ionizing flux create H ii regions rich with star formation. Studying the distribution and abundance of young stellar objects (YSOs) in these ionized bubbles can provide essential insight into the physical processes that shape their formation, allowing us to test competing models of star formation. In this work, we examined one such OB association, Cepheus OB4 (Cep OB4)—a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created a photometric catalog from Spitzer/Infrared Array Camera (IRAC) mosaics in bands 1 (3.6 μm) and 2 (4.5 μm). We supplemented the catalog with photometry from the Wide-field Infrared Survey Explorer, the Two Micron All Sky Survey, IRAC bands 3 (5.8 μm) and 4 (8.0 μm), MIPS 24 μm, and MMIRS near-infrared data. We used color–color selections to identify 821 YSOs, which we classified using the IR slope of the YSOs’ spectral energy distributions, finding 67 Class I, 103 flat spectrum, 569 Class II, and 82 Class III YSOs. We conducted a clustering analysis of the Cep OB4 YSOs and fit their spectral energy distributions. We found many young Class I objects distributed in the surrounding shell and pillars as well as a relative age gradient of unclustered sourcesin the bubble surrounding the OB association, with YSOs generally decreasing in age with distance from the central cluster. Both of these results indicate that the expansion of the H ii region may have triggered star formation in CepOB4.

Exploring the voids: Luminosity functions and magnetic field

We present semi-analytical models for magnetisation of the void inter-galactic medium (IGM) by outflows from void galaxies. The number density of dark matter haloes in an under-dense region (i.e., void) is obtained using the excursion set method extended for such low density environment. The star formation in such haloes has been estimated, taking account of the negative feedback by supernovae. The galaxy formation/evolution model is tuned to provide the r-band luminosity function, the stellar mass function and also the color of void galaxies as obtained from recent observations. This star formation model is used to study possible outflows from void galaxies driven by the hot thermal gas and cosmic ray pressures. These outflows drag the magnetic fields present in those galaxies to the void IGM. We show that such a model can magnetise ∼30% of the void IGM with the magnetic field strength of 10−12−10−10 G while considering only magnetic flux freezing condition. Along with this, the megapersec size of individual outflows can explain the non-detection of GeV photons in TeV blazars that put a lower limit of 10−16 G for void IGM magnetic field with a Mpc coherent length scale.

Regulation of star formation by large-scale gravitoturbulence

ABSTRACT A simple model for star formation based on supernova (SN) feedback and gravitational heating via the collapse of perturbations in gravitationally unstable discs reproduces the Schmidt–Kennicutt relation between the star formation rate (SFR) per unit area, ΣSFR, and the gas surface density, Σg, remarkably well. The gas velocity dispersion, σg, is derived self-consistently in conjunction with ΣSFR and is found to match the observations. Gravitational instability triggers ‘gravitoturbulence’ at the scale of the least stable perturbation mode, boosting σg at $\Sigma _{g}\gtrsim \, \Sigma _{g}^\textrm {thr}=50\, {\rm M}_\odot \, {\rm pc}^{-2}$, and contributing to the pressure needed to carry the disc weight vertically. ΣSFR is reduced to the observed level at $\Sigma _{g}\gtrsim \, \Sigma _{g}^\textrm {thr}$, whereas at lower surface densities, SN feedback is the prevailing energy source. Our proposed star formation recipes require efficiencies of the order of 1 per cent, and the Toomre parameter, Q, for the joint gaseous and stellar disc is predicted to be close to the critical value for marginal stability for $\Sigma _{g}\lesssim \, \Sigma _{g}^\textrm {thr}$, spreading to lower values and larger gas velocity dispersion at higher Σg.

Extended Hernquist–Springel formalism for cosmic star formation

ABSTRACT We present a revised and extended version of the analytical model for cosmic star formation originally given by Hernquist and Springel in 2003. The key assumption of this formalism is that star formation proceeds from cold gas, at a rate that is limited by an internal consumption time-scale at early times, or by the rate of generation of gas via cooling at late times. These processes are analysed as a function of the mass of dark matter haloes and integrated over the halo population. We modify this approach in two main ways to make it more general: (1) halo collapse times are included explicitly, so that the behaviour is physically reasonable at late times; (2) allowance is made for a mass-dependent baryon fraction in haloes, which incorporates feedback effects. This model reproduces the main features of the observed baryonic Tully–Fisher relationship, and is consistent with observational estimates of the baryon mass fraction in the intergalactic medium. With minimal adjustment of parameters, our approach reproduces the observed history of cosmic star formation within a factor of 2 over the redshift range of 0 < z < 10. This level of agreement is comparable to that achieved by state-of-the-art cosmological simulations. Our simplified apparatus has pedagogical value in illuminating the results of such detailed calculations, and also serves as a means for rapid approximate exploration of non-standard cosmological models.

Evolution of the Gas Density in a Simulated Star-forming Cloud with Stellar Feedback

Abstract Star formation involves gravity, turbulence, magnetic fields, and feedback from new stars through jets, radiation and winds. The evolution of the density probability distribution function (ρ-PDF) is directly related to the star formation rate (SFR), forming the basis of several star formation models. We utilize two runs from the STARFORGE simulation suite that follow the evolution of molecular clouds, while resolving individual stars and including all gas and feedback physics. The two runs have different initial conditions, one is a periodic box with driven turbulence (Box), while the other is an isolated cloud without turbulent driving (Sphere). We find that the ρ-PDF for both runs is initially well-fit by a log-normal (LN) plus a power-law (PL) function. However, as the SFR peaks, the PDF for the Sphere run becomes well-fit by just a wide LN. Conversely, the Box run PDF remains well-fit by a LN+PL function for the entirety of the run.

Impact of relativistic jets on the star formation rate: a turbulence-regulated framework

ABSTRACT 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.

Revealing the formation histories of the first stars with the cosmic near-infrared background

ABSTRACT The cosmic near-infrared background (NIRB) offers a powerful integral probe of radiative processes at different cosmic epochs, including the pre-reionization era when metal-free, Population III (Pop III) stars first formed. While the radiation from metal-enriched, Population II (Pop II) stars likely dominates the contribution to the observed NIRB from the reionization era, Pop III stars – if formed efficiently – might leave characteristic imprints on the NIRB, thanks to their strong Lyα emission. Using a physically motivated model of first star formation, we provide an analysis of the NIRB mean spectrum and anisotropy contributed by stellar populations at z > 5. We find that in circumstances where massive Pop III stars persistently form in molecular cooling haloes at a rate of a few times $10^{-3}\, \mathrm{ M}_\odot \ \mathrm{yr}^{-1}$, before being suppressed towards the epoch of reionization (EoR) by the accumulated Lyman–Werner background, a unique spectral signature shows up redward of $1\, \mu$m in the observed NIRB spectrum sourced by galaxies at z > 5. While the detailed shape and amplitude of the spectral signature depend on various factors including the star formation histories, initial mass function, LyC escape fraction and so forth, the most interesting scenarios with efficient Pop III star formation are within the reach of forthcoming facilities, such as the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer. As a result, new constraints on the abundance and formation history of Pop III stars at high redshifts will be available through precise measurements of the NIRB in the next few years.

Find the Gap: Black Hole Population Analysis with an Astrophysically Motivated Mass Function

Abstract We introduce a novel black hole mass function that realistically models the physics of pair-instability supernovae with a minimal number of parameters. Applying this to all events in the LIGO-Virgo Gravitational-Wave Transient Catalog 2 (GWTC-2), we detect a peak at M BHMG = 46 − 6 + 17 M ⊙ . Repeating the analysis without the black holes from the event GW190521, we find this feature at M BHMG = 54 ± 6 M ⊙. These results establish the edge of the anticipated “black hole mass gap” at a value compatible with the expectation from standard stellar structure theory. The mass gap manifests itself as a discontinuity in the mass function and is populated by a distinct, less-abundant population of higher-mass black holes. We find that the primary black hole population scales with power-law index −1.95 ± 0.51 (−1.97 ± 0.44) with (without) GW190521, consistent with models of star formation. Using Bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as pre-existing phenomenological mass functions. We also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics.

A Deep Census of Outlying Star Formation in the M101 Group

Abstract We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying H ii regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O iii], to detect potential outlying star-forming regions. Our survey covers ∼6 deg2 around M101, and we detect objects in emission down to an Hα flux level of 5.7 × 10−17 erg s−1 cm−2 (equivalent to a limiting star formation rate of 1.7 × 10−6 M ⊙ yr−1 at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands and 8 objects in emission in Hα and [O iii]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying H ii regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93%) are consistent with being M101 outer-disk H ii regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486 and a faint outlying H ii region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless H i clouds near M101. The lack of any hidden population of low-luminosity star-forming dwarfs around M101 suggests a rather shallow faint-end slope (as flat as α ∼ −1.0) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally triggered star formation models and the interaction history of the M101 Group.

An observational testbed for cosmological zoom-in simulations: constraining stellar migration in the solar cylinder using asteroseismology

ABSTRACT Large-scale stellar surveys coupled with recent developments in magneto-hydrodynamical simulations of the formation of Milky Way-mass galaxies provide an unparalleled opportunity to unveil the physical processes driving the evolution of the Galaxy. We developed a framework to compare a variety of parameters with their corresponding predictions from simulations in an unbiased manner, taking into account the selection function of a stellar survey. We applied this framework to a sample of over 7000 stars with asteroseismic, spectroscopic, and astrometric data available, together with six simulations from the Auriga project. We found that some simulations are able to produce abundance dichotomies in the [Fe/H]−[α/Fe] plane which look qualitatively similar to observations. The peak of their velocity distributions match the observed data reasonably well; however, they predict hotter kinematics in terms of the tails of the distributions and the vertical velocity dispersion. Assuming our simulation sample is representative of Milky Way-like galaxies, we put upper limits of 2.21 and 3.70 kpc on radial migration for young (<4 Gyr) and old (∈[4, 8] Gyr) stellar populations in the solar cylinder. Comparison between the observed and simulated metallicity dispersion as a function of age further constrains migration to about 1.97 and 2.91 kpc for the young and old populations. These results demonstrate the power of our technique to compare numerical simulations with high-dimensional data sets, and paves the way for using the wider field TESS asteroseismic data together with the future generations of simulations to constrain the sub-grid models for turbulence, star formation, and feedback processes.

A Spitzer survey for dust-obscured supernovae

ABSTRACT Supernova (SN) rates serve as an important probe of star formation models and initial mass functions. Near-infrared seeing-limited ground-based surveys typically discover a factor of 3–10 fewer SNe than predicted from far-infrared luminosities owing to sensitivity limitations arising from both a variable point-spread function (PSF) and high dust extinction in the nuclear regions of star-forming galaxies. This inconsistency has potential implications for our understanding of star-formation rates and massive-star evolution, particularly at higher redshifts, where star-forming galaxies are more common. To resolve this inconsistency, a successful SN survey in the local universe must be conducted at longer wavelengths and with a space-based telescope, which has a stable PSF to reduce the necessity for any subtraction algorithms and thus residuals. Here, we report on a 2-yr Spitzer/IRAC 3.6 $\mu$m survey for dust-extinguished SNe in the nuclear regions of forty luminous infrared galaxies (LIRGs) within 200 Mpc. The asymmetric Spitzer PSF results in worse than expected subtraction residuals when implementing standard template subtraction. Forward-modelling techniques improve our sensitivity by several ∼1.5 mag. We report the detection of 9 SNe, five of which were not discovered by optical surveys. After adjusting our predicted rates to account for the sensitivity of our survey, we find that the number of detections is consistent with the models. While this search is none the less hampered by a difficult-to-model PSF and the relatively poor resolution of Spitzer, it will benefit from future missions, such as Roman and the James Webb Space Telescope, with higher resolution and more symmetric PSFs.

Probing Feedback via IGM tomography and the Lyα Forest with Subaru PFS, TMT/ELT, and JWST

Abstract In preparation for the tomography study of the intergalactic medium (IGM) by Subaru Prime Focus Spectrograph (PFS) survey and other large future telescopes such as TMT/ELT/GMT, we present the results of our pilot study on Lyα forest and IGM tomography statistics using the GADGET3-Osaka cosmological smoothed particle hydrodynamical simulation. Our simulation includes models for star formation and supernova feedback, which enables more realistic cross-correlation studies between galaxies, neutral hydrogen (H i), and metals in circumgalactic and intergalactic medium. We create a light-cone data set at z = 2–3 from our simulations and generate mock Lyα forest data. As a first step, in this paper, we focus on the distribution of H i and galaxies, and present statistical results on 1D flux probability distribution function, 1D power spectrum, flux contrast versus impact parameter, and H i–galaxy cross-correlations. Our results show overall agreement with current observational data, with some interesting discrepancies on small scales that are due to either feedback effects or varying observational conditions. Our simulation shows stronger H i absorption with decreasing transverse distance from galaxies. We find that massive galaxies with M ⋆ ≥ 1010 M ⊙ contribute strongly to the flux contrast signal, and that lower-mass galaxies with M ⋆ ∼ 108–1010 M ⊙ tend to dilute the flux contrast signal from massive galaxies. On large scales, the average flux contrast smoothly connects to the IGM level, supporting the concordance Λ cold dark matter model. We also find an increase in the H i absorption toward the center of a protocluster.

SIRIUS project. I. Star formation models for star-by-star simulations of star clusters and galaxy formation

Abstract Most stars are formed as star clusters in galaxies, which then disperse into galactic disks. Upcoming exascale supercomputational facilities will enable simulations of galaxies and their formation by resolving individual stars (star-by-star simulations). This will substantially advance our understanding of star formation in galaxies, star cluster formation, and assembly histories of galaxies. In previous galaxy simulations, a simple stellar population approximation was used. It is, however, difficult to improve the mass resolution with this approximation. Therefore, a model for forming individual stars that can be used in simulations of galaxies must be established. In this first paper of a series from the SIRIUS (SImulations Resolving IndividUal Stars) project, we demonstrate a stochastic star formation model for star-by-star simulations. An assumed stellar initial mass function (IMF) is randomly assigned to newly formed stars in this model. We introduce a maximum search radius to assemble the mass from surrounding gas particles to form star particles. In this study, we perform a series of N-body/smoothed particle hydrodynamics simulations of star cluster formations from turbulent molecular clouds and ultra-faint dwarf galaxies as test cases. The IMF can be correctly sampled if a maximum search radius that is larger than the value estimated from the threshold density for star formation is adopted. In small clouds, the formation of massive stars is highly stochastic because of the small number of stars. We confirm that the star formation efficiency and threshold density do not strongly affect the results. We find that our model can naturally reproduce the relationship between the most massive stars and the total stellar mass of star clusters. Herein, we demonstrate that our models can be applied to simulations varying from star clusters to galaxies for a wide range of resolutions.

Improving models of the cosmic infrared background using CMB lensing mass maps

The cosmic infrared background (CIB) sourced by infrared emission from dusty star-forming galaxies is a valuable source of information on the star formation history of the Universe. In measurements of the millimeter sky at frequencies higher than $\ensuremath{\sim}300\text{ }\text{ }\mathrm{GHz}$, the CIB and thermal emission from Galactic dust dominate. Insufficient understanding of the CIB contribution at lower frequencies can hinder efforts to measure the kinetic Sunyaev-Zeldovich spectrum on small scales as well as new physics that affects the damping tail of the cosmic microwave background (CMB). The Planck satellite has measured with high fidelity the CIB at 217, 353, 545 and 857 GHz. On very large scales, this measurement is limited by our ability to separate the CIB from Galactic dust, but on intermediate scales, the measurements are limited by sample variance in the underlying matter field traced by the CIB. We show how significant improvements (20--100%) can be obtained on parameters of star formation models by cross-correlating the CIB (as measured from existing Planck maps or upcoming CCAT-prime maps) with upcoming mass maps inferred from gravitational lensing of the CMB. This improvement comes from improved knowledge of the redshift distribution of star-forming galaxies as well as through the use of the unbiased matter density inferred from CMB lensing mass maps to cancel the sample variance in the CIB field. We also find that further improvements can be obtained on CIB model parameters if the cross-correlation of the CIB with CMB lensing is measured over a wider area while restricting the more challenging CIB autospectrum measurement to the cleanest 5% of the sky.