Origins Space Telescope: Predictions for far-IR spectroscopic surveys

2020

ApJ

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Recent estimates point to abundances of z > 4 sub-mm galaxies far above model predictions. The matter is still debated. According to some analyses the excess may be substantially lower than initially thought and perhaps accounted for by flux boosting and source blending. However, there is no general agreement on this conclusion. An excess of z > 6 dusty galaxies has also been reported albeit with poor statistics. On the other hand, Zhang et al. (2018) reported evidence of a top-heavy initial mass function (IMF) in high-z galaxies. This would translate into higher a sub-mm luminosity of dusty galaxies at fixed star-formation rate (SFR), i.e., into a higher abundance of high-z galaxies than expected for an universal IMF. Exploiting the physical model by Cai et al. (2013) we argue that some excess can be understood in terms of a somewhat top-heavier IMF for proto-spheroidal galaxies compared to late-type galaxies. Such IMF is consistent with that advocated by Zhang et al. (2018) to account for the low 13 C/ 18 O abundance ratio measured by them in four z = 2-3 dusty galaxies. However, the IMF impact on the star formation history of galaxies is far less dramatic than suggested by these authors and extreme top-heavy IMFs are inconsistent with the data.

Section: Discussionmentioning

confidence: 99%

High-z Dusty Star-forming Galaxies: A Top-heavy Initial Mass Function?

Cai

Zotti

2020

ApJ

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“…Strongly lensed galaxies detected by CMB experiments will be obvious targets for the next generation Very Large Array (ngVLA) that will provide accurate estimates of the molecular outflow masses and mass loss rates up to z 4 [57]. The proposed NASA flagship Origins Space Telescope [OST; 58,59] would detect molecular, neutral, and warm ionized phases of outflows up to higher redshifts, although with a spatial resolution lower than ngVLA. AGN-driven outflows also produce a bubble of hot gas, potentially detectable via its Sunyaev-Zeldovich effect [SZE; 60,61].…”

Section: Astrophysics and Cosmography With Strong Lensingmentioning

confidence: 99%

Extragalactic Astrophysics With Next-Generation CMB Experiments

Zotti

Front. Astron. Space Sci.

Negrello

et al. 2019

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Planck, SPT and ACT surveys have clearly demonstrated that Cosmic Microwave Background (CMB) experiments, while optimised for cosmological measurements, have made important contributions to the field of extragalactic astrophysics in the last decade. Future CMB experiments have the potential to make even greater contributions. One example is the detection of highz galaxies with extreme gravitational amplifications. The combination of flux boosting and of stretching of the images has allowed the investigation of the structure of galaxies at z 3 with the astounding spatial resolution of about 60 pc. Another example is the detection of proto-clusters of dusty galaxies at high z when they may not yet possess the hot intergalactic medium allowing their detection in X-rays or via the Sunyaev-Zeldovich effect. Next generation CMB experiments, like PICO, CORE, CMB-Bharat from space and Simons Observatory and CMB-S4 from the ground, will discover several thousands of strongly lensed galaxies out to z ∼ 6 or more and of 1 arXiv:1907.05323v1 [astro-ph.GA] 11 Jul 2019 De Zotti et al. Running Title Figure 1. Effect of angular resolution on the confusion limit. The filled blue circles show the differential counts of sources on SPT maps degraded to the PICO resolution at 150 GHz (FWHM = 6.2 ; left panel) and 220 GHz (FWHM = 3.6 ; right panel) compared with the SPT counts of Mocanu et al. [5, orange stars]. The vertical dot-dashed lines correspond, from left to right, to the 90% completeness limits at the full SPT resolution, at the PICO resolution and at the Planck resolution.galaxy proto-clusters caught in the phase when their member galaxies where forming the bulk of their stars. They will also detect tens of thousands of local dusty galaxies and thousands of radio sources at least up to z 5. Moreover they will measure the polarized emission of thousands of radio sources and of dusty galaxies at mm/sub-mm wavelengths.

“…The line-L IR relations obtained by Bonato et al (2019) are based on observations of dusty galaxies, for which the unabsorbed fraction of the emission from young stars is small, so that L IR is a measure of the total SFR. One might wonder whether the line luminosities are primarily related to L IR or to the SFR and an answer was provided by De Looze et al (2014).…”

Section: Line-detection Limitsmentioning

confidence: 99%

“…Based on these results, following Bonato et al (2019) we assume that the luminosity of FIR fine-structure lines primarily correlates with the SFR. Thus, the relations derived by Bonato et al (2019) allow us to estimate the values of SFR as a function of z corresponding to the 5 σ line-detection limits listed in Table 1. The results are shown in Fig.…”

Section: Tablementioning

confidence: 99%

“…A 6-month duration survey of 5 % sky is also being considered; it goes deeper by a factor of approximately √ 5. Exploiting observations, mostly from Spitzer and Herschel, Bonato et al (2019) reported tight correlations between the main mid-IR-to-submm lines from neutral or ionized atomic gas and from molecular gas and the total IR luminosity, L IR (conventionally defined over 8-1000 µm), of dust heated by newly formed stars.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Understanding galaxy formation and evolution through an all-sky submillimetre spectroscopic survey

Negrello

Publ. Astron. Soc. Aust.

Cai

et al. 2020

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We illustrate the extraordinary discovery potential for extragalactic astrophysics of a far-infrared/submillimetre (far-IR/submm) all-sky spectroscopic survey with a 3-m-class space telescope. Spectroscopy provides a three-dimensional view of the Universe and allows us to take full advantage of the sensitivity of present-day instrumentation, close to fundamental limits, overcoming the spatial confusion that affects broadband far-IR/submm surveys. A space telescope of the 3-m class (which has already been described in recent papers) will detect emission lines powered by star formation in galaxies out to $z\,{\simeq}\,8$ . It will specifically provide measurements of spectroscopic redshifts, star-formation rates (SFRs), dust masses, and metal content for millions of galaxies at the peak epoch of cosmic star formation and of hundreds of them at the epoch of reionisation. Many of these star-forming galaxies will be strongly lensed; the brightness amplification and stretching of their sizes will make it possible to investigate (by means of follow-up observations with high-resolution instruments like ALMA, JWST, and SKA) their internal structure and dynamics on the scales of giant molecular clouds (40–100 pc). This will provide direct information on the physics driving the evolution of star-forming galaxies. Furthermore, the arcmin resolution of the telescope at submm wavelengths is ideal for detecting the cores of galaxy proto-clusters, out to the epoch of reionisation. Due to the integrated emission of member galaxies, such objects (as well as strongly lensed sources) will dominate at the highest apparent far-IR luminosities. Tens of millions of these galaxy-clusters-in-formation will be detected at $z \simeq 2 - 3$ –3, with a tail extending out to $z\,{\simeq}\,7$ , and thousands of detections at $6\,{<}\,z\,{<}\,7$ . Their study will allow us to track the growth of the most massive halos well beyond what is possible with classical cluster surveys (mostly limited to $z\,\lesssim\, 1.5 - 2$ –2), tracing the history of star formation in dense environments and teaching us how star formation and galaxy-cluster formation are related across all epochs. The obscured cosmic SFR density of the Universe will thereby be constrained. Such a survey will overcome the current lack of spectroscopic redshifts of dusty star-forming galaxies and galaxy proto-clusters, representing a quantum leap in far-IR/submm extragalactic astrophysics.