scholarly journals On the FRB luminosity function – – II. Event rate density

2020 ◽  
Vol 494 (1) ◽  
pp. 665-679 ◽  
Author(s):  
Rui Luo ◽  
Yunpeng Men ◽  
Kejia Lee ◽  
Weiyang Wang ◽  
D R Lorimer ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Event Rate ◽  
Local Environment ◽  
Companion Paper ◽  
Host Galaxy ◽  
Selection Effects ◽  
Radio Bursts ◽  
Searching Strategy ◽  
Electron Distributions ◽  
Power Law Index

ABSTRACT The luminosity function of Fast Radio Bursts (FRBs), defined as the event rate per unit cosmic co-moving volume per unit luminosity, may help to reveal the possible origins of FRBs and design the optimal searching strategy. With the Bayesian modelling, we measure the FRB luminosity function using 46 known FRBs. Our Bayesian framework self-consistently models the selection effects, including the survey sensitivity, the telescope beam response, and the electron distributions from Milky Way/ the host galaxy/ local environment of FRBs. Different from the previous companion paper, we pay attention to the FRB event rate density and model the event counts of FRB surveys based on the Poisson statistics. Assuming a Schechter luminosity function form, we infer (at the 95 per cent confidence level) that the characteristic FRB event rate density at the upper cut-off luminosity $L^*=2.9_{-1.7}^{+11.9}\times 10^{44}\, \mathrm{erg}\, \mathrm{s}^{-1}$ is $\phi ^*=339_{-313}^{+1074}\, \mathrm{Gpc}^{-3}\, \mathrm{yr}^{-1}$, the power-law index is $\alpha =-1.79_{-0.35}^{+0.31}$, and the lower cut-off luminosity is $L_0\le 9.1\times 10^{41}\, \mathrm{erg}\, \mathrm{s}^{-1}$. The event rate density of FRBs is found to be $3.5_{-2.4}^{+5.7}\times 10^4\, \mathrm{Gpc}^{-3}\, \mathrm{yr}^{-1}$ above $10^{42}\, \mathrm{erg}\, \mathrm{s}^{-1}$, $5.0_{-2.3}^{+3.2}\times 10^3\, \mathrm{Gpc}^{-3}\, \mathrm{yr}^{-1}$ above $10^{43}\, \mathrm{erg}\, \mathrm{s}^{-1}$ , and $3.7_{-2.0}^{+3.5}\times 10^2\, \mathrm{Gpc}^{-3}\, \mathrm{yr}^{-1}$ above $10^{44}\, \mathrm{erg}\, \mathrm{s}^{-1}$. As a result, we find that, for searches conducted at 1.4 GHz, the optimal diameter of single-dish radio telescopes to detect FRBs is 30–40 m. The possible astrophysical implications of the measured event rate density are also discussed in the current paper.

scholarly journals High time resolution and polarization properties of ASKAP-localized fast radio bursts

2020 ◽  
Vol 497 (3) ◽  
pp. 3335-3350 ◽  
Author(s):  
Cherie K Day ◽  
Adam T Deller ◽  
Ryan M Shannon ◽  
Hao Qiu(邱昊) ◽  
Keith W Bannister ◽  
...  
Keyword(s):  
Time Resolution ◽  
Local Environment ◽  
High Time ◽  
Frequency Resolution ◽  
Host Galaxy ◽  
High Time Resolution ◽  
Radio Bursts ◽  
Diverse Range ◽  
Scattering Time ◽  
The Impact

ABSTRACT Combining high time and frequency resolution full-polarization spectra of fast radio bursts (FRBs) with knowledge of their host galaxy properties provides an opportunity to study both the emission mechanism generating them and the impact of their propagation through their local environment, host galaxy, and the intergalactic medium. The Australian Square Kilometre Array Pathfinder (ASKAP) telescope has provided the first ensemble of bursts with this information. In this paper, we present the high time and spectral resolution, full polarization observations of five localized FRBs to complement the results published for the previously studied ASKAP FRB 181112. We find that every FRB is highly polarized, with polarization fractions ranging from 80 to 100 per cent, and that they are generally dominated by linear polarization. While some FRBs in our sample exhibit properties associated with an emerging archetype (i.e. repeating or apparently non-repeating), others exhibit characteristic features of both, implying the existence of a continuum of FRB properties. When examined at high time resolution, we find that all FRBs in our sample have evidence for multiple subcomponents and for scattering at a level greater than expected from the Milky Way. We find no correlation between the diverse range of FRB properties (e.g. scattering time, intrinsic width, and rotation measure) and any global property of their host galaxy. The most heavily scattered bursts reside in the outskirts of their host galaxies, suggesting that the source-local environment rather than the host interstellar medium is likely the dominant origin of the scattering in our sample.

scholarly journals Exploring the epoch of hydrogen reionization using FRBs

2021 ◽  
Author(s):  
Paz Beniamini ◽  
Pawan Kumar ◽  
Xiangcheng Ma ◽  
Eliot Quataert
Keyword(s):  
Optical Depth ◽  
Luminosity Function ◽  
High Redshift ◽  
Thomson Scattering ◽  
Host Galaxy ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Average Electron Density ◽  
Average Electron ◽  
Better Than

Abstract We describe three different methods for exploring the hydrogen reionization epoch using fast radio bursts (FRBs) and provide arguments for the existence of FRBs at high redshift (z). The simplest way, observationally, is to determine the maximum dispersion measure (DMmax) of FRBs for an ensemble that includes bursts during the reionization. The DMmax provides information regarding reionization much like the optical depth of the CMB to Thomson scattering does, and it has the potential to be more accurate than constraints from Planck, if DMmax can be measured to a precision better than 500 pccm−3. Another method is to measure redshifts of about 40 FRBs between z of 6-10 with$\sim 10\%$ accuracy to obtain the average electron density in 4 different z-bins with $\sim 4\%$ accuracy. These two methods don’t require knowledge of the FRB luminosity function and its possible redshift evolution. Finally, we show that the reionization history is reflected in the number of FRBs per unit DM, given a fluence limited survey of FRBs that includes bursts during the reionization epoch; we show using FIRE simulations that the contributions to DM from the FRB host galaxy & CGM during the reionization era is a small fraction of the observed DM. This third method requires no redshift information but does require knowledge of the FRB luminosity function.

scholarly journals Joint inference on the redshift distribution of fast radio burst and on the intergalactic baryon content

2020 ◽  
Author(s):  
S Hackstein ◽  
M Brüggen ◽  
F Vazza
Keyword(s):  
Radio Burst ◽  
Intergalactic Medium ◽  
Local Environment ◽  
Dispersion Measure ◽  
Selection Effects ◽  
Radio Bursts ◽  
Host Galaxies ◽  
Redshift Distribution ◽  
Joint Inference ◽  
Fast Radio Burst

Abstract Context: Fast radio bursts are transient radio pulses of extragalactic origin. Their dispersion measure is indicative of the baryon content in the ionized intergalactic medium between the source and the observer. However, inference using unlocalized fast radio bursts is degenerate to the distribution of redshifts of host galaxies. Method: We perform a joint inference of the intergalactic baryon content and the fast radio burst redshift distribution with the use of Bayesian statistics by comparing the likelihood of different models to reproduce the observed statistics in order to infer the most likely models. In addition to two models of the intergalactic medium, we consider contributions from the local environment of the source, assumed to be a magnetar, as well as a representative ensemble of host and intervening galaxies. Results: Assuming that the missing baryons reside in the ionized intergalactic medium, our results suggest that the redshift distribution of observed fast radio bursts peaks at z ≲ 0.6. However, conclusions from different instruments regarding the intergalactic baryon content diverge and thus require additional changes to the observed distribution of host redshifts, beyond those caused by telescope selection effects.

scholarly journals Fast radio burst dispersion measures and rotation measures and the origin of intergalactic magnetic fields

2019 ◽  
Vol 488 (3) ◽  
pp. 4220-4238 ◽  
Author(s):  
S Hackstein ◽  
M Brüggen ◽  
F Vazza ◽  
B M Gaensler ◽  
V Heesen
Keyword(s):  
Magnetic Fields ◽  
Radio Burst ◽  
Milky Way ◽  
Intergalactic Medium ◽  
Local Environment ◽  
Distribution Functions ◽  
Host Galaxy ◽  
Radio Bursts ◽  
Dispersion Measures ◽  
Fast Radio Burst

ABSTRACT We investigate the possibility of measuring intergalactic magnetic fields using the dispersion measures and rotation measures of fast radio bursts. With Bayesian methods, we produce probability density functions for values of these measures. We distinguish between contributions from the intergalactic medium, the host galaxy, and the local environment of the progenitor. To this end, we use constrained, magnetohydrodynamic simulations of the local Universe to compute lines-of-sight integrals from the position of the Milky Way. In particular, we differentiate between predominantly astrophysical and primordial origins of magnetic fields in the intergalactic medium. We test different possible types of host galaxies and probe different distribution functions of fast radio burst progenitor locations inside the host galaxy. Under the assumption that fast radio bursts are produced by magnetars, we use analytic predictions to account for the contribution of the local environment. We find that less than 100 fast radio bursts from magnetars in stellar-wind environments hosted by starburst dwarf galaxies at redshift z ≳ 0.5 suffice to discriminate between predominantly primordial and astrophysical origins of intergalactic magnetic fields. However, this requires the contribution of the Milky Way to be removed with a precision of ≈1 rad m−2. We show the potential existence of a subset of fast radio bursts whose rotation measures carry information on the strength of the intergalactic magnetic field and its origins.

scholarly journals Non-detection of fast radio bursts from six gamma-ray burst remnants with possible magnetar engines

2019 ◽  
Vol 489 (3) ◽  
pp. 3643-3647 ◽  
Author(s):  
Yunpeng Men ◽  
Kshitij Aggarwal ◽  
Ye Li ◽  
Divya Palaniswamy ◽  
Sarah Burke-Spolaor ◽  
...  
Keyword(s):  
Detection Probability ◽  
Luminosity Function ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Host Galaxy ◽  
Radio Bursts ◽  
Left Behind ◽  
Central Engine ◽  
Fast Radio Burst ◽  
Green Bank Telescope

ABSTRACT The analogy of the host galaxy of the repeating fast radio burst (FRB) source FRB 121102 and those of long gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe) has led to the suggestion that young magnetars born in GRBs and SLSNe could be the central engine of repeating FRBs. We test such a hypothesis by performing dedicated observations of the remnants of six GRBs with evidence of having a magnetar central engine using the Arecibo telescope and the Robert C. Byrd Green Bank Telescope (GBT). A total of ∼20 h of observations of these sources did not detect any FRB from these remnants. Under the assumptions that all these GRBs left behind a long-lived magnetar and that the bursting rate of FRB 121102 is typical for a magnetar FRB engine, we estimate a non-detection probability of 8.9 × 10−6. Even though these non-detections cannot exclude the young magnetar model of FRBs, we place constraints on the burst rate and luminosity function of FRBs from these GRB targets.

scholarly journals A targeted search for repeating fast radio bursts associated with gamma-ray bursts

2020 ◽  
Vol 501 (1) ◽  
pp. 541-547
Author(s):  
Nipuni T Palliyaguru ◽  
Devansh Agarwal ◽  
Golnoosh Golpayegani ◽  
Ryan Lynch ◽  
Duncan R Lorimer ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Radio Bursts ◽  
Upper Limits ◽  
Show Evidence ◽  
The One ◽  
Power Law Index ◽  
Arecibo Observatory ◽  
Green Bank Telescope

ABSTRACT The origin of fast radio bursts (FRBs) still remains a mystery, even with the increased number of discoveries in the last 3 yr. Growing evidence suggests that some FRBs may originate from magnetars. Large, single-dish telescopes such as Arecibo Observatory (AO) and Green Bank Telescope (GBT) have the sensitivity to detect FRB 121102-like bursts at gigaparsec distances. Here, we present searches using AO and GBT that aimed to find potential radio bursts at 11 sites of past gamma-ray bursts that show evidence for the birth of a magnetar. We also performed a search towards GW170817, which has a merger remnant whose nature remains uncertain. We place $10\sigma$ fluence upper limits of ≈0.036 Jy ms at 1.4 GHz and ≈0.063 Jy ms at 4.5 GHz for the AO data and fluence upper limits of ≈0.085 Jy ms at 1.4 GHz and ≈0.098 Jy ms at 1.9 GHz for the GBT data, for a maximum pulse width of ≈42 ms. The AO observations had sufficient sensitivity to detect any FRB of similar luminosity to the one recently detected from the Galactic magnetar SGR 1935+2154. Assuming a Schechter function for the luminosity function of FRBs, we find that our non-detections favour a steep power-law index (α ≲ −1.1) and a large cut-off luminosity (L0 ≳ 1041 erg s−1).

scholarly journals Correlations between H α equivalent width and galaxy properties at z = 0.47: Physical or selection-driven?

2021 ◽  
Vol 503 (4) ◽  
pp. 5115-5133
Author(s):  
A A Khostovan ◽  
S Malhotra ◽  
J E Rhoads ◽  
S Harish ◽  
C Jiang ◽  
...  
Keyword(s):  
Star Formation ◽  
Equivalent Width ◽  
Luminosity Function ◽  
Mass Function ◽  
Stellar Mass ◽  
High Mass ◽  
Selection Effects ◽  
Star Formation Activity ◽  
Low Mass ◽  
Stellar Masses

ABSTRACT The H α equivalent width (EW) is an observational proxy for specific star formation rate (sSFR) and a tracer of episodic, bursty star-formation activity. Previous assessments show that the H α EW strongly anticorrelates with stellar mass as M−0.25 similar to the sSFR – stellar mass relation. However, such a correlation could be driven or even formed by selection effects. In this study, we investigate how H α EW distributions correlate with physical properties of galaxies and how selection biases could alter such correlations using a z = 0.47 narrow-band-selected sample of 1572 H α emitters from the Ly α Galaxies in the Epoch of Reionization (LAGER) survey as our observational case study. The sample covers a 3 deg2 area of COSMOS with a survey comoving volume of 1.1 × 105 Mpc3. We assume an intrinsic EW distribution to form mock samples of H α emitters and propagate the selection criteria to match observations, giving us control on how selection biases can affect the underlying results. We find that H α EW intrinsically correlates with stellar mass as W0∝M−0.16 ± 0.03 and decreases by a factor of ∼3 from 107 M⊙ to 1010 M⊙, while not correcting for selection effects steepens the correlation as M−0.25 ± 0.04. We find low-mass H α emitters to be ∼320 times more likely to have rest-frame EW>200 Å compared to high-mass H α emitters. Combining the intrinsic W0–stellar mass correlation with an observed stellar mass function correctly reproduces the observed H α luminosity function, while not correcting for selection effects underestimates the number of bright emitters. This suggests that the W0–stellar mass correlation when corrected for selection effects is physically significant and reproduces three statistical distributions of galaxy populations (line luminosity function, stellar mass function, EW distribution). At lower stellar masses, we find there are more high-EW outliers compared to high stellar masses, even after we take into account selection effects. Our results suggest that high sSFR outliers indicative of bursty star formation activity are intrinsically more prevalent in low-mass H α emitters and not a byproduct of selection effects.

scholarly journals A fast radio burst source at a complex magnetised site in a barred galaxy

2021 ◽  
Author(s):  
K.J. Lee ◽  
Heng Xu ◽  
J.R. Niu ◽  
P. Chen ◽  
Weiwei Zhu ◽  
...  
Keyword(s):  
Optical Observations ◽  
Host Galaxy ◽  
Radio Bursts ◽  
Radio Waves ◽  
Galactocentric Distance ◽  
Burst Source ◽  
Radiation Mechanism ◽  
Circular Polarisation ◽  
Rotation Measure ◽  
Fast Radio Burst

Abstract Fast radio bursts (FRBs) are highly dispersed radio bursts prevailing in the universe. The recent detection of FRB~200428 from a Galactic magnetar suggested that at least some FRBs originate from magnetars, but it is unclear whether the majority of cosmological FRBs, especially the actively repeating ones, are produced from the magnetar channel. Here we report the detection of 1863 polarised bursts from the repeating source FRB~20201124A during a dedicated radio observational campaign of Five-hundred-meter Aperture Spherical radio Telescope (FAST). The large sample of radio bursts detected in 88 hr over 54 days indicate a significant, irregular, short-time variation of the Faraday rotation measure (RM) of the source during the first 36 days, followed by a constant RM during the later 18 days. Significant circular polarisation up to 75\% was observed in a good fraction of bursts. Evidence suggests that some low-level circular polarisation originates from the conversion from linear polarisation during the propagation of the radio waves, but an intrinsic radiation mechanism is required to produce the higher degree of circular polarisation. All of these features provide evidence for a more complicated, dynamically evolving, magnetised immediate environment around this FRB source. Its host galaxy was previously known. Our optical observations reveal that it is a Milky-Way-sized, metal-rich, barred-spiral galaxy at redshift z=0.09795+-0.00003, with the FRB residing in a low stellar density, interarm region at an intermediate galactocentric distance, an environment not directly expected for a young magnetar formed during an extreme explosion of a massive star.

scholarly journals Extending the White Dwarf Sequence: Plans and Prospects

1978 ◽  
Vol 80 ◽  
pp. 437-440
Author(s):  
James Liebert
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Selection Effects ◽  
Number Density ◽  
Low Velocity ◽  
Luminosity Functions ◽  
Current Sample ◽  
The Many

The recent discovery that the parallax star LP701-29 is a white dwarf has firmly extended the degenerate sequence below MV= +16m(Dahnet al. 1978). As the search for white dwarfs extends to cooler and fainter stars, however, it becomes particularly important to develop a plan for selecting candidates among the many thousands of red proper motion stars. We begin by assessing the completeness of the known sample within 10 parsecs in the northern two thirds of the sky. Some color-dependent selection effects must be evaluated, however, since these may preferentially inhibit the discovery of cooler stars. A correction factor for the missing low velocity white dwarfs is estimated. Then, Green's(1977) recent determination of the number density of blue degenerates is used to normalize various theoretical luminosity functions, the benchmarks against which the current sample out to 10 pc can be compared. It is concluded that the sample may be approaching completeness in the northern sky for white dwarfs with tangential velocities (vT) ≥ 40 km/sec (μ ≥ 1″.0/yr.) and Mbol< +15m. The implied luminosity function is thus consistent with that found by Sion and Liebert (1977). Below Mbol= +15mthe different theoretical functions predict substantially different numbers.

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