Dusty Star-Forming Galaxies (DSFGs), also known as Sub-mm galaxies (SMGs), are a rare population of dusty galaxies with incredibly high star formation rates (Wilkins et al., 2018), leading to string emission in the FIR - sub-mm. Predicting them in hydrodynamic cosmological simulations has been a challenge for a number of years, but we presented one of the best matches to date from the Simba simulation (Lovell et al., 2021), using the Powderday dust radiative transfer code (Narayanan et al., 2021). We also explored the dependence of the FIR-submm emission on orientation, and found interesting dependencies on inclination (Lovell et al., 2022).
Dependence of the 850-micron emission on star formation rate and dust mass, as predicted by Simba.
I’m now part of the wider AtLAST project, exploring how this proposed large single-dish observatory could revolutionise the study of DSFGs / SMGs (van Kampen et al., 2024).
References
2024
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Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Surveying the distant Universe
Eelco Kampen, Tom Bakx, Carlos De Breuck, and 27 more authors
arXiv e-prints, Mar 2024
During the most active period of star formation in galaxies, which occurs in the redshift range 1\textlessz\textless3, strong bursts of star formation result in significant quantities of dust, which obscures new stars being formed as their UV/optical light is absorbed and then re-emitted in the infrared, which redshifts into the mm/sub-mm bands for these early times. To get a complete picture of the high-z galaxy population, we need to survey a large patch of the sky in the sub-mm with sufficient angular resolution to resolve all galaxies, but we also need the depth to fully sample their cosmic evolution, and therefore obtain their redshifts using direct mm spectroscopy with a very wide frequency coverage. This requires a large single-dish sub-mm telescope with fast mapping speeds at high sensitivity and angular resolution, a large bandwidth with good spectral resolution and multiplex spectroscopic capabilities. The proposed 50-m Atacama Large Aperture Submillimeter Telescope (AtLAST) will deliver these specifications. We discuss how AtLAST allows us to study the whole population of high-z galaxies, including the dusty star-forming ones which can only be detected and studied in the sub-mm, and obtain a wealth of information for each of these up to z~7: gas content, cooling budget, star formation rate, dust mass, and dust temperature. We present worked examples of surveys that AtLAST can perform, both deep and wide, and also focused on galaxies in proto-clusters. In addition we show how such surveys with AtLAST can measure the growth rate and the Hubble constant with high accuracy, and demonstrate the power of the line-intensity mapping method in the mm/sub-mm wavebands to constrain the cosmic expansion history at high redshifts, as good examples of what can uniquely be done by AtLAST in this research field.
2022
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An orientation bias in observations of submillimetre galaxies
C. C. Lovell, J. E. Geach, R. Davé, and 5 more authors
MNRAS, Sep 2022
ADS Bibcode: 2022MNRAS.515.3644L
Recent high-resolution interferometric images of submillimetre galaxies (SMGs) reveal fascinatingly complex morphologies. This raises a number of questions: how does the relative orientation of a galaxy affect its observed submillimetre emission, and does this result in an ’orientation bias’ in the selection and analysis of such galaxies in flux-limited cosmological surveys? We investigated these questions using the SIMBA cosmological simulation paired with the dust radiative transfer code POWDERDAY. We selected eight simulated SMGs (S850 ≳ 2 mJy) at z = 2, and measured the variance of their ’observed’ emission over 50 random orientations. Each galaxy exhibits significant scatter in its emission close to the peak of the thermal dust emission, with variation in flux density of up to a factor of 2.7. This results in an appreciable dispersion in the inferred dust temperatures and infrared luminosities (16th-84th percentile ranges of 5 K and 0.1 dex, respectively) and therefore a fundamental uncertainty in derived parameters such as dust mass and star formation rate (~30 per cent for the latter using simple calibrations). Using a Monte Carlo simulation we also assessed the impact of orientation on flux-limited surveys, finding a bias in the selection of SMGs towards those with face-on orientations, as well as those at lower redshifts. We predict that the orientation bias will affect flux-limited single-dish surveys, most significantly at THz frequencies, and this bias should be taken into account when placing the results of targeted follow-up studies in a statistical context.
2021
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Reproducing submillimetre galaxy number counts with cosmological hydrodynamic simulations
Christopher C. Lovell, James E. Geach, Romeel Davé, and 2 more authors
MNRAS, Mar 2021
Matching the number counts of high-z submillimetre-selected galaxies (SMGs) has been a long-standing problem for galaxy formation models. In this paper, we use 3D dust radiative transfer to model the submm emission from galaxies in the SIMBA cosmological hydrodynamic simulations, and compare predictions to the latest single-dish observational constraints on the abundance of 850 μm-selected sources. We find good agreement with the shape of the integrated 850 μm luminosity function, and the normalization is within 0.25 dex at \textgreater3 mJy, unprecedented for a fully cosmological hydrodynamic simulation, along with good agreement in the redshift distribution of bright SMGs. The agreement is driven primarily by SIMBA’s good match to infrared measures of the star formation rate (SFR) function between z = 2 and 4 at high SFRs. Also important is the self-consistent on-the-fly dust model in SIMBA, which predicts, on average, higher dust masses (by up to a factor of 2.5) compared to using a fixed dust-to-metals ratio of 0.3. We construct a light-cone to investigate the effect of far-field blending, and find that 52 per cent of sources are blends of multiple components, which makes a small contribution to the normalization of the bright end of the number counts. We provide new fits to the 850 μm luminosity as a function of SFR and dust mass. Our results demonstrate that solutions to the discrepancy between submm counts in simulations and observations, such as a top-heavy initial mass function, are unnecessary, and that submillimetre-bright phases are a natural consequence of massive galaxy evolution.
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powderday: Dust Radiative Transfer for Galaxy Simulations
Desika Narayanan, Matthew J. Turk, Thomas Robitaille, and 18 more authors
ApJS, Jan 2021
Publisher: American Astronomical Society
We present powderday (available at https://github.com/dnarayanan/powderday), a flexible, fast, open-source dust radiative transfer package designed to interface with both idealized and cosmological galaxy formation simulations. powderday builds on fsps stellar population synthesis models, and hyperion dust radiative transfer, and employs yt to interface between different software packages. We include our stellar population synthesis modeling on the fly, allowing significant flexibility in the assumed stellar physics and nebular line emission. The dust content follows either simple observationally motivated prescriptions (i.e., constant dust-to-metals ratios, or dust-to-gas ratios that vary with metallicity), direct modeling from galaxy formation simulations that include dust physics, as well as a novel approach that includes the dust content via learning-based algorithms from the simba cosmological galaxy formation simulation. Active galactic nuclei (AGNs) can additionally be included via a range of prescriptions. The output of these models are broadband (912 Å–1 mm) spectral energy distributions (SEDs), as well as filter-convolved monochromatic images. powderday is designed to eliminate last-mile efforts by researchers that employ different hydrodynamic galaxy formation models and seamlessly interfaces with gizmo, arepo, gasoline, changa, and enzo. We demonstrate the capabilities of the code via three applications: a model for the star formation rate–infrared luminosity relation in galaxies (including the impact of AGNs), the impact of circumstellar dust around AGB stars on the mid-infrared emission from galaxy SEDs, and the impact of galaxy inclination angle on dust attenuation laws.
2018
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Dust-obscured star-forming galaxies in the early universe
Stephen M. Wilkins, Yu Feng, Tiziana Di Matteo, and 3 more authors
MNRAS, Feb 2018
Motivated by recent observational constraints on dust reprocessed emission in star-forming galaxies at z ∼ 6 and above, we use the very large cosmological hydrodynamical simulation BLUETIDES to explore predictions for the amount of dust-obscured star formation in the early Universe (z \textgreater 8). BLUETIDES matches current observational constraints on both the UV luminosity function and galaxy stellar mass function and predicts that approximately 90 per cent of the star formation in high-mass (M* \textgreater 1010 M⊙) galaxies at z = 8 is already obscured by dust. The relationship between dust attenuation and stellar mass predicted by BLUETIDES is consistent with that observed at lower redshift. However, observations of several individual objects at z \textgreater 6 are discrepant with the predictions, though it is possible that their uncertainties may have been underestimated. We find that the predicted surface density of z ≥ 8 submm sources is below that accessible to current Herschel, SCUBA-2 and Atacama Large Millimetre Array (ALMA) submm surveys. However, as ALMA continues to accrue an additional surface area the population of z \textgreater 8 dust-obscured galaxies may become accessible in the near future.
