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Context.Fast radio bursts (FRBs) are very energetic pulses in the radio wavelengths that have an unknown physical origin. They can be used to study the intergalactic medium thanks to their dispersion measure (DM). The DM has several contributions that can be measured (or estimated), including the contribution from the host galaxy itself, DMhost. The DMhostis generally difficult to measure, thus limiting the use of FRBs as cosmological probes and our understanding of their physical origin(s). Aims.In this work we empirically estimated DMhostfor a sample of 12 galaxy hosts of well-localized FRBs at 0.11 < z < 0.53 using a direct method based solely on the properties of the host galaxies themselves, referred to as DMhostdirect. We also explored possible correlations between DMhostand some key global properties of galaxies. Methods.We used VLT/MUSE observations of the FRB hosts to estimate our empirical DMhostdirect. The method relies on estimating the DM contribution of both the FRB host galaxy’s interstellar medium (DMhostISM) and its halo (DMhosthalo) separately. For comparison purposes, we also provide an alternative indirect method for estimating DMhostbased on the Macquart relation (DMhostMacquart). Results.We find an average ⟨DMhost⟩ = 80 ± 11 pc cm−3with a standard deviation of 38 pc cm−3(in the rest frame) using our direct method, with a systematic uncertainty of ∼30%. This is larger than the typically used value of 50 pc cm−3but consistent within the uncertainties. We report positive correlations between DMhostand both the stellar masses and the star formation rates of their hosts galaxies. In contrast, we do not find any strong correlation between DMhostand the redshift nor the projected distances to the center of the FRB hosts. Finally, we do not find any strong correlation between DMhostdirectand DMhostMacquart, although the average values of the two are consistent within the uncertainties. Conclusions.Our reported correlations between DMhostdirectand stellar masses and/or the star formation rates of the galaxies could be used in future studies to improve the priors used in establishing DMhostfor individual FRBs. Similarly, such correlations and the lack of a strong redshift evolution can be used to constrain models for the progenitor of FRBs, for example by comparing them with theoretical models. However, the lack of correlation between DMhostdirectand DMhostdirectindicates that there may be contributions to the DM of FRBs not included in our DMhostdirectmodeling, for example large DMs from the immediate environment of the FRB progenitor and/or intervening large-scale structures not accounted for in DMhostMacquart.
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Single Pulse Dispersion Measure of the Crab Pulsar
Abstract We investigate the use of bright single pulses from the Crab pulsar to determine separately the dispersion measure (DM) for the Main Pulse and Interpulse components. We develop two approaches using cross-correlation functions (CCFs). The first method computes the CCF of the total intensity of each of the 64 frequency channels with a reference channel and converts the time lag of maximum correlation into a DM. The second method separately computes the CCF between every pair of channels for each individual bright pulse and extracts an average DM from the distribution of all channel-pair DMs. Both methods allow the determination of the DM with a relative uncertainty of better than 10−5and provide robust estimates for the uncertainty of the best-fit value. We find differences in DM between the Main Pulse, the Low Frequency Interpulse, and the High Frequency Interpulse using both methods in a frequency range from 4 to 6 GHz. Earlier observations of the High Frequency Interpulse carried out by Hankins et al. (2016) resulted in DMHFIP–DMMPof 0.010 ± 0.016 pc cm−3. Our results indicate a DMHFIP–DMMPof 0.0127 ± 0.0011 pc cm−3(with DMcompbeing the DM value of the respective emission component), confirming earlier results with an independent method. During our studies we also find a relation between the brightness of single pulses in the High Frequency Interpulse and their DM. We also discuss the application of the developed methods on the identification of substructures in the case of Fast Radio Bursts.
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- Award ID(s):
- 2020265
- PAR ID:
- 10369820
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 935
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 84
- Size(s):
- Article No. 84
- Sponsoring Org:
- National Science Foundation
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