arXiv subjects

Tiger Y. -Y. Hsiao

Publications and source records attributed to Tiger Y. -Y. Hsiao.

At least 19 recordsLinked to original sources

arXiv2026

PRISMS. GHZ1. A standard tale of galaxy evolution with atypical ionizing conditions at $z=9.878$

[Abridged] The first operating years of the James Webb Space Telescope (JWST) have revealed a surprising number of $z \gtrsim 10$ UV-bright objects, many of them characterized by their compactness, anomalous chemical abundance patterns and complex ISM physics (e.g. N-enhanced systems). To assess whether these objects are a phase of early galaxy evolution or a peculiar population, it is essential to understand the physics of systems without anomalous abundance patterns in this epoch. We present a detailed analysis of GHZ1 ($z=9.878$), a moderately ($μ= 1.715$) lensed UV-bright ($M_{UV} = -20.07$) galaxy in the Abell2744 field, characterized by an extended size ($R_{e} \sim 410$ pc). These properties, which contrast with the properties of many of the N-enhanced galaxies, make GHZ1 an excellent laboratory to assess what are the major drivers of early galaxy evolution and the origin of the differences. By means of JWST spectroscopic observations from NIRSpec (PRISM-CLEAR configuration) and the MIR/LRS, we analyzed the full UV and optical emission from GHZ1. We used a spectro-photometric SED fitting to characterize the stellar evolution and the emission line spectra to constrain its chemical enrichment. We find that GHZ1 is among the most massive systems at $z\sim 10$ (log(M$_{\star}$ [M$_{\odot}$]) = 9.17$_{-0.26}^{+0.27}$), with a moderate amount of dust attenuation ($A_{V} = 0.21_{-0.12}^{+0.12}$~mag) and ongoing star formation (with a median SFR $= 8.75_{-1.72}^{+1.71}$ M$_{\odot}\cdot$yr$^{-1}$ over the last 10 Myr). Its chemical enrichment patterns (12+log(O/H) = $7.81_{-0.11}^{+0.12}$, log(C/O) = $-0.66_{-0.13}^{+0.13}$, log(N/O)$< -1.04$) are consistent with a standard evolution dominated by primary production from massive stars. We also derive an H$α$/H$β$ Balmer ratio below Case B predictions. We speculate that [...].

astro-ph.GA↗

arXiv2026

Other red dots: A possible GLIMPSE of normal AGB stars at Cosmic Noon through extreme lensing

We report the discovery of four extremely faint ($m_{\mathrm{F444W}}\gtrsim29$) red point sources in recent ultra-deep JWST/NIRCam images of the strong lensing galaxy cluster Abell S1063. All four sources sit in lensed arcs, on the symmetry points very close to the critical curves for their host-galaxies' redshifts ($z\sim1-4$). Remarkably, these point sources appear in most arcs that are sufficiently faint close to the critical curve's position ($<21\,\mathrm{nJy}\,\mathrm{arcsec}^{-2}$ in F115W). This suggests that -- unlike previous caustic-crossing events or lensed stars -- thanks to the unprecedented depth of the GLIMPSE observations paired with the extreme lensing magnification (up to $μ\sim10^4$) we might be resolving the lower-mass ($M\sim1-11\,\mathrm{M}_{\odot}$) red stellar population. Concretely, we detect three likely extremely magnified asymptotic giant branch (AGB) stars ($T_{\mathrm{eff}}\sim3200-3750$ K), and one yellow super-giant star ($T_{\mathrm{eff}}\sim6750$ K) -- possibly a yellow hyper-giant or a Cepheid. In addition to offering the first glimpse at low-mass extremely magnified stars, these detections open a possible window into stellar populations, evolution, and chemical enrichment at high redshifts, and could pave the way for using lensed stars such as these as standard candles to populate the distance ladder at cosmological redshifts.

astro-ph.GA↗

arXiv2023

Reaching for the stars -- JWST/NIRSpec spectroscopy of a lensed star candidate at $z=4.76$

We present JWST/NIRSpec observations of a highly magnified star candidate at a photometric redshift of $z_{\mathrm{phot}}\simeq4.8$, previously detected in JWST/NIRCam imaging of the strong lensing (SL) cluster MACS J0647+7015 ($z=0.591$). The spectroscopic observation allows us to precisely measure the redshift of the host arc at $z_{\mathrm{spec}}=4.758\pm0.004$, and the star's spectrum displays clear Lyman- and Balmer-breaks commensurate with this redshift. A fit to the spectrum suggests a B-type super-giant star of surface temperature $T_{\mathrm{eff,B}}\simeq15000$ K with either a redder F-type companion ($T_{\mathrm{eff,F}}\simeq6250$K) or significant dust attenuation ($A_V\simeq0.82$) along the line of sight. We also investigate the possibility that this object is a magnified young globular cluster rather than a single star. We show that the spectrum is in principle consistent with a star cluster, which could also accommodate the lack of flux variability between the two epochs. However, the lack of a counter image and the strong upper limit on the size of the object from lensing symmetry, $r\lesssim0.5$ pc, could indicate that this scenario is somewhat less likely -- albeit not completely ruled out by the current data. The presented spectrum seen at a time when the Universe was only $\sim1.2$ Gyr old showcases the ability of JWST to study early stars through extreme lensing.

astro-ph.GA↗

arXiv2023

A T-Dwarf Candidate from JWST Early Release NIRCam data

We present a distant T$-$type brown dwarf candidate at $\approx2.55$ kpc discovered in the Cosmic Evolution Early Release Science (CEERS) fields by James Webb Space Telescope (JWST) NIRCam. In addition to the superb sensitivity, we utilised 7 filters from JWST in near-IR and thus is advantageous in finding faint, previously unseen brown dwarfs. From the model spectra in new JWST/NIRCam filter wavelengths, the selection criteria of F115W-F277W$<$-0.8 and F277W-F444W$>$1.1 were chosen to target the spectrum features of brown dwarfs having temperatures from 500K to 1300K. Searching through the data from Early Release Observations (ERO) and Early Release Science (ERS), we find 1 promising candidate in the CEERS field. The result of SED fitting suggested an early T spectral type with a low effective temperature of T$_\text{eff}\approx$1300K, the surface gravity of $\log{g}\approx5.25\text{cm s}^{-2}$, and an eddy diffusion parameter of logK$_{zz}\approx7\text{cm}^2 \text{s}^{-1}$, which indicates an age of $\approx$1.8Gyr and a mass of $\approx0.05$M$_{\odot}$. In contrast to typically found T$-$dwarf within several hundred parsecs, the estimated distance of the source is $\approx2.55$kpc, showing the JWST's power to extend the search to a much larger distance.

astro-ph.SR↗

arXiv2023

Future Constraints on Dark Matter with Gravitationally Lensed Fast Radio Bursts Detected by BURSTT

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

astro-ph.HE↗

arXiv2023

Classifying a frequently repeating fast radio burst, FRB 20201124A, with unsupervised machine learning

Fast radio bursts (FRBs) are astronomical transients with millisecond timescales. Although most of the FRBs are not observed to repeat, a few of them are detected to repeat more than hundreds of times. There exist a large variety of physical properties among these bursts, suggesting heterogeneous mechanisms of FRBs. In this paper, we conduct a categorisation on the extremely frequently repeating FRB 20201124A with the assistance of machine learning, as such techniques have the potential to use subtle differences and correlations that humans are unaware of to better classify bursts. The research is carried out by applying the unsupervised Uniform Manifold Approximation and Projection (UMAP) model on the FRB 20201124A data provided by Five-hundred-meter Aperture Spherical radio Telescope (FAST). The algorithm eventually categorises the bursts into three clusters. In addition to the two categories in previous work based on waiting time, a new way for categorisation has been found. The three clusters are either high energy, high frequency, or low frequency, reflecting the distribution of FRB energy and frequency. Importantly, a similar machine learning result is found in another frequently repeating FRB20121102A, implying a common mechanism among this kind of FRB. This work is one of the first steps towards the systematical categorisation of the extremely frequently repeating FRBs.

astro-ph.HE↗

arXiv2022

Detection Rate of Fast Radio Bursts in the Milky Way with BURSTT

Fast radio bursts (FRBs) are intense bursts of radio emission with durations of milliseconds. Although researchers have found them happening frequently all over the sky, they are still in the dark to understand what causes the phenomena because the existing radio observatories have encountered certain challenges during the discovery of FRB progenitors. The construction of Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is being proposed to solve these challenges. We simulate mock Galactic FRB-like events by applying a range of spatial distributions, pulse widths and luminosity functions. The effect of turbulent Interstellar Medium (ISM) on the detectability of FRB-like events within the Milky Way plane is considered to estimate the dispersion measure and pulse scattering of mock events. We evaluate the fraction of FRB-like events in the Milky Way that are detectable by BURSTT and compare the result with those by Survey for Transient Astronomical Radio Emission 2 (STARE2) and Galactic Radio Explorer (GReX). We find that BURSTT could increase the detection rate by more than two orders of magnitude compared with STARE2 and GReX, depending on the slope of luminosity function of the events. We also investigate the influence of the specifications of BURSTT on its detection improvement. This leads to the fact that greatly higher sensitivity and improved coverage of the Milky Way plane have significant effects on the detection improvement of BURSTT. We find that the upgrade version of BURSTT, BURSTT-2048 could increase the detection rate of faint Galactic FRB-like events by a factor of 3.

astro-ph.HE↗

arXiv2022

BURSTT: Bustling Universe Radio Survey Telescope in Taiwan

Fast Radio Bursts (FRBs) are bright millisecond-duration radio transients that appear about 1,000 times per day, all-sky, for a fluence threshold 5 Jy ms at 600 MHz. The FRB radio-emission physics and the compact objects involved in these events are subjects of intense active debate. To better constrain source models, the Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is optimized to discover and localize a large sample of rare, high-fluence, nearby FRBs. This is the population most amenable to multi-messenger, multi-wavelength follow-up, allowing deeper understanding of source mechanisms. BURSTT will provide horizon-to-horizon sky coverage with a half power field-of-view (FoV) of $\sim$10$^{4}$ deg$^{2}$, a 400 MHz effective bandwidth between 300-800 MHz, and sub-arcsecond localization, made possible using outrigger stations hundreds to thousands of km from the main array. Initially, BURSTT will employ 256 antennas. After tests of various antenna designs and optimization of system performance we plan to expand to 2048 antennas. We estimate that BURSTT-256 will detect and localize $\sim$100 bright ($\geq$100 Jy ms) FRBs per year. Another advantage of BURSTT's large FoV and continuous operation will be greatly enhanced monitoring of FRBs for repetition. The current lack of sensitive all-sky observations likely means that many repeating FRBs are currently cataloged as single-event FRBs.

astro-ph.IM↗

arXiv2022

Can luminous Lyman alpha emitters at $z$ $\simeq$ 5.7 and $z$ $\simeq$ 6.6 suppress star formation?

Addressing how strong UV radiation affects galaxy formation is central to understanding their evolution. The quenching of star formation via strong UV radiation (from starbursts or AGN) has been proposed in various scenes to solve certain astrophysical problems. Around luminous sources, some evidence of decreased star formation has been found but is limited to a handful of individual cases. No direct, conclusive evidence on the actual role of strong UV radiation in quenching star formation has been found. Here we present statistical evidence of decreased number density of faint (AB magnitude $\geq$ 24.75 mag) Lyαemitters (LAEs) around bright (AB magnitude < 24.75 mag) LAEs even when the radius goes up to 10 pMpc for $z$ $\simeq$ 5.7 LAEs. A similar trend is found for z $\simeq$ 6.6 LAEs but only within 1 pMpc radius from the bright LAEs. We use a large sample of 1077 (962) LAEs at $z$ $\simeq$ 5.7 ($z$ $\simeq$ 6.6) selected in total areas of 14 (21) deg$^2$ with Subaru/Hyper Suprime-Cam narrow-band data, and thus, the result is of statistical significance for the first time at these high redshift ranges. A simple analytical calculation indicates that the radiation from the central LAE is not enough to suppress LAEs with AB mag $\geq$ 24.75 mag around them, suggesting additional physical mechanisms we are unaware of are at work. Our results clearly show that the environment is at work for the galaxy formation at $z$ $\sim$ 6 in the Universe.

astro-ph.GA↗

arXiv2022

ALMA [O III] and [C II] Detections of A1689-zD1 at $z=7.13$

A1689-zD1 is one of the most distant galaxies, discovered with the aid of gravitational lensing, providing us with an important opportunity to study galaxy formation in the very early Universe. In this study, we report the detection of [C II]158$μ$m and [O III]88$μ$m emission lines of A1689-zD1 in the ALMA Bands 6 and 8. We measure the redshift of this galaxy as $z_{\rm{sys}}=7.133\pm0.005$ based on the [C II] and [O III] emission lines, consistent with that adopted by Bakx et al. (2021). The observed $L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ ratio is $2.09\pm0.09$, higher than most of the local galaxies, but consistent with other $z\sim7$ galaxies. The moderate-spatial resolution of ALMA data provided us with a precious opportunity to investigate spatial variation of $L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$. In contrast to the average value of 2.09, we find a much higher $L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ of $\sim 7$ at the center of the galaxy. This spatial variation of $L_{[\rm{O\,III]}}/L_{[\rm{C\,II]}}$ was seldom reported for other high-z galaxies. It is also interesting that the peak of the ratio does not overlap with optical peaks. Possible physical reasons include a central AGN, shock heating from merging, and starburst. Our moderate-spatial resolution data also reveals that in addition to the observed two clumps shown in previous HST images, there is a redshifted segment to the west of the northern optical clump. Such a structure is consistent with previous claims that A1689-zD1 is a merging galaxy, but with the northern redshifted part being some ejected materials, or that the northern redshifted materials being from a third more highly obscured region of the galaxy.

astro-ph.GA↗

arXiv2022

Energy functions of fast radio bursts derived from the first CHIME/FRB catalogue

Fast radio bursts (FRBs) are mysterious millisecond pulses in radio, most of which originate from distant galaxies. Revealing the origin of FRBs is becoming central in astronomy. The redshift evolution of the FRB energy function, i.e., the number density of FRB sources as a function of energy, provides important implications for the FRB progenitors. Here we show the energy functions of FRBs selected from the recently released Canadian Hydrogen Intensity Mapping Experiment (CHIME) catalogue using the $V_{\rm max}$ method. The $V_{\rm max}$ method allows us to measure the redshift evolution of the energy functions as it is without any prior assumption on the evolution. We use a homogeneous sample of 164 non-repeating FRB sources, which are about one order of magnitude larger than previously investigated samples. The energy functions of non-repeating FRBs show Schechter function-like shapes at $z\lesssim1$. The energy functions and volumetric rates of non-repeating FRBs decrease towards higher redshifts similar to the cosmic stellar-mass density evolution: there is no significant difference between the non-repeating FRB rate and cosmic stellar-mass density evolution with a 1\% significance threshold, whereas the cosmic star-formation rate scenario is rejected with a more than 99\% confidence level. Our results indicate that the event rate of non-repeating FRBs is likely controlled by old populations rather than young populations which are traced by the cosmic star-formation rate density. This suggests old populations such as old neutron stars and black holes as more likely progenitors of non-repeating FRBs.

astro-ph.HE↗

arXiv2021

Upper limits on Einstein's weak equivalence principle placed by uncertainties of dispersion measures of fast radio bursts

Fast radio bursts (FRBs) are astronomical transients with millisecond timescales occurring at cosmological distances. The observed time lag between different energies of each FRB is well described by the inverse-square law of the observed frequency, i.e., dispersion measure. Therefore, FRBs provide one of the ideal laboratories to test Einstein's weak equivalence principle (WEP): the hypothetical time lag between photons with different energies under a gravitational potential. If WEP is violated, such evidence should be exposed within the observational uncertainties of dispersion measures, unless the WEP violation also depends on the inverse-square of the observed frequency. In this work, we constrain the difference of gamma parameters ($Δγ$) between photons with different energies using the observational uncertainties of FRB dispersion measures, where $Δγ=0$ for Einstein's general relativity. Adopting the averaged 'Shapiro time delay' for cosmological sources, FRB 121002 at $z=1.6\pm0.3$ and FRB 180817.J1533+42 at $z=1.0\pm0.2$ place the most stringent constraints of $\logΔγ<-20.8\pm0.1$ and $\log(Δγ/r_{E}) < -20.9\pm0.2$, respectively, where $r_{E}$ is the energy ratio between the photons. The former is about three orders of magnitude lower than those of other astrophysical sources in previous works under the same formalization of the Shapiro time delay while the latter is comparable to the tightest constraint so far.

gr-qc↗

arXiv2021

Constraining violations of the Weak Equivalence Principle Using CHIME FRBs

Einstein's General Relativity (GR) is the basis of modern astronomy and astrophysics. Testing the validity of basic assumptions of GR is important. In this work, we test a possible violation of the Weak Equivalence Principle (WEP), i.e., there might be a time-lag between photons of different frequencies caused by the effect of gravitational fields if the speeds of photons are slightly different at different frequencies. We use Fast Radio Bursts (FRBs) , which are astronomical transients with millisecond timescales detected in the radio frequency range. Being at cosmological distances, accumulated time delay of FRBs can be caused by the plasma in between an FRB source and an observer, and by gravitational fields in the path of the signal. We segregate the delay due to dispersion and gravitational field using the post-Newtonian formalism (PPN) parameter $Δγ$, which defines the space-curvature due to gravity by a unit test mass. We did not detect any time-delay from FRBs but obtained tight constraints on the upper limit of $Δγ$. For FRB20181117C with $z = 1.83 \pm 0.28$ and $ν_{obs}$ = $676.5\,{\rm MHz}$, the best possible constraint is obtained at log($Δγ$) = $-21.58 ^{+0.10}_{-0.12}$ and log($Δγ$/$r_{\rm E}$) = $-21.75 ^{+0.10}_{-0.14}$, respectively, where $r_{\rm E}$ is the energy ratio of two photons of the same FRB signal. This constraint is about one order of magnitude better than the previous constraint obtained with FRBs, and five orders tighter than any constraint obtained using other cosmological sources.

gr-qc↗

arXiv2021

Uncloaking hidden repeating fast radio bursts with unsupervised machine learning

The origins of fast radio bursts (FRBs), astronomical transients with millisecond timescales, remain unknown. One of the difficulties stems from the possibility that observed FRBs could be heterogeneous in origin; as some of them have been observed to repeat, and others have not. Due to limited observing periods and telescope sensitivities, some bursts may be misclassified as non-repeaters. Therefore, it is important to clearly distinguish FRBs into repeaters and non-repeaters, to better understand their origins. In this work, we classify repeaters and non-repeaters using unsupervised machine learning, without relying on expensive monitoring observations. We present a repeating FRB recognition method based on the Uniform Manifold Approximation and Projection (UMAP). The main goals of this work are to: (i) show that the unsupervised UMAP can classify repeating FRB population without any prior knowledge about their repetition, (ii) evaluate the assumption that non-repeating FRBs are contaminated by repeating FRBs, and (iii) recognise the FRB repeater candidates without monitoring observations and release a corresponding catalogue. We apply our method to the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) database. We found that the unsupervised UMAP classification provides a repeating FRB completeness of 95 per cent and identifies 188 FRB repeater source candidates from 474 non-repeater sources. This work paves the way to a new classification of repeaters and non-repeaters based on a single epoch observation of FRBs.

astro-ph.HE↗

arXiv2021

Revealing the cosmic reionisation history with fast radio bursts in the era of Square Kilometre Array

Revealing the cosmic reionisation history is at the frontier of extragalactic astronomy. The power spectrum of the cosmic microwave background (CMB) polarisation can be used to constrain the reionisation history. Here we propose a CMB-independent method using fast radio bursts (FRBs) to directly measure the ionisation fraction of the intergalactic medium (IGM) as a function of redshift. FRBs are new astronomical transients with millisecond timescales. Their dispersion measure (DM$_{\rm IGM}$) is an indicator of the amount of ionised material in the IGM. Since the differential of DM$_{\rm IGM}$ against redshift is proportional to the ionisation fraction, our method allows us to directly measure the reionisation history without any assumption on its functional shape. As a proof of concept, we constructed mock non-repeating FRB sources to be detected with the Square Kilometre Array, assuming three different reionisation histories with the same optical depth of Thomson scattering. We considered three cases of redshift measurements: (A) spectroscopic redshift for all mock data, (B) spectroscopic redshift for 10% of mock data, and (C) redshift estimated from an empirical relation of FRBs between their time-integrated luminosity and rest-frame intrinsic duration. In all cases, the reionisation histories are consistently reconstructed from the mock FRB data using our method. Our results demonstrate the capability of future FRBs in constraining the reionisation history.

astro-ph.CO↗

arXiv2021

An Active Galactic Nucleus Recognition Model based on Deep Neural Network

To understand the cosmic accretion history of supermassive black holes, separating the radiation from active galactic nuclei (AGNs) and star-forming galaxies (SFGs) is critical. However, a reliable solution on photometrically recognising AGNs still remains unsolved. In this work, we present a novel AGN recognition method based on Deep Neural Network (Neural Net; NN). The main goals of this work are (i) to test if the AGN recognition problem in the North Ecliptic Pole Wide (NEPW) field could be solved by NN; (ii) to shows that NN exhibits an improvement in the performance compared with the traditional, standard spectral energy distribution (SED) fitting method in our testing samples; and (iii) to publicly release a reliable AGN/SFG catalogue to the astronomical community using the best available NEPW data, and propose a better method that helps future researchers plan an advanced NEPW database. Finally, according to our experimental result, the NN recognition accuracy is around 80.29% - 85.15%, with AGN completeness around 85.42% - 88.53% and SFG completeness around 81.17% - 85.09%.

astro-ph.GA↗

arXiv2020

No redshift evolution of non-repeating fast radio-burst rates

Fast radio bursts (FRBs) are millisecond transients of unknown origin(s) occurring at cosmological distances. Here we, for the first time, show time-integrated-luminosity functions and volumetric occurrence rates of non-repeating and repeating FRBs against redshift. The time-integrated-luminosity functions of non-repeating FRBs do not show any significant redshift evolution. The volumetric occurrence rates are almost constant during the past $\sim$10 Gyr. The nearly-constant rate is consistent with a flat trend of cosmic stellar-mass density traced by old stellar populations. Our findings indicate that the occurrence rate of non-repeating FRBs follows the stellar-mass evolution of long-living objects with $\sim$Gyr time scales, favouring e.g. white dwarfs, neutron stars, and black holes, as likely progenitors of non-repeating FRBs. In contrast, the occurrence rates of repeating FRBs may increase towards higher redshifts in a similar way to the cosmic star formation-rate density or black hole accretion-rate density if the slope of their luminosity function does not evolve with redshift. Short-living objects with $\lesssim$ Myr time scales associated with young stellar populations (or their remnants, e.g., supernova remnants, young pulsars, and magnetars) or active galactic nuclei might be favoured as progenitor candidates of repeating FRBs.

astro-ph.HE↗

arXiv2020

Fast radio bursts to be detected with the Square Kilometre Array

Fast radio bursts (FRBs) are mysterious extragalactic radio signals. Revealing their origin is one of the central foci in modern astronomy. Previous studies suggest that occurrence rates of non-repeating and repeating FRBs could be controlled by the cosmic stellar-mass density (CSMD) and star formation-rate density (CSFRD), respectively. The Square Kilometre Array (SKA) is one of the best future instruments to address this subject due to its high sensitivity and high-angular resolution. Here, we predict the number of FRBs to be detected with the SKA. In contrast to previous predictions, we estimate the detections of non-repeating and repeating FRBs separately, based on latest observational constraints on their physical properties including the spectral indices, FRB luminosity functions, and their redshift evolutions. We consider two cases of redshift evolution of FRB luminosity functions following either the CSMD or CSFRD. At $z\gtrsim2$, $z\gtrsim6$ and $z\gtrsim10$, non-repeating FRBs will be detected with the SKA at a rate of $\sim10^{4}$, $\sim10^{2}$, and $\sim10$ (sky$^{-1}$ day$^{-1}$), respectively, if their luminosity function follows the CSMD evolution. At $z\gtrsim1$, $z\gtrsim2$, and $z\gtrsim4$, sources of repeating FRBs will be detected at a rate of $\sim10^{3}$, $\sim10^{2}$, and $\lesssim10$ (sky$^{-1}$ day$^{-1}$), respectively, assuming that the redshift evolution of their luminosity function is scaled with the CSFRD. These numbers could change by about one order of magnitude depending on the assumptions on the CSMD and CSFRD. In all cases, abundant FRBs will be detected by the SKA, which will further constrain the luminosity functions and number density evolutions.

astro-ph.HE↗