arXiv subjects

Elizabeth K. Mahony

Publications and source records attributed to Elizabeth K. Mahony.

At least 19 recordsLinked to original sources

arXiv2026

A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH - II. Direct observations and stacking of 21 cm line

We present results of a search for associated and intervening HI 21 cm absorption in star-forming galaxies and a control sample of radio galaxies at 0.4 < $z$ < 1.0, using ASKAP's FLASH HI 21 cm absorption survey. We report the detection of a new HI 21 cm absorption line in radio galaxy NVSS J214954-004657 at $z_{\mathrm{HI}}$ = 0.863. Additionally, we present results of HI 21 cm stacking for associated and intervening star-forming and radio galaxy catalogues. For the first time at these redshifts, we report tentative detections of stacked HI 21 cm absorption for associated galaxies when stacked in order of descending radio source brightness, and show that these tentative detections become buried as optical depth increases as progressively weaker sources are co-added into the stack. No stacked signal is detected when co-adding intervening galaxy spectra. We speculate that the ability to detect a stacked HI 21 cm detection is dependent on the background source optical depth limits, as well as source covering factors. Covering factor has a greater impact when stacking intervening systems, and can be considered to effectively weaken the observed flux density of a radio source. We find no significant difference in detection rate for associated HI 21 cm absorption in star-forming galaxies versus the general radio-source population at the same redshift. Although detection rates are low, from a meta-analysis of HI 21 cm surveys we find that 1 detection is expected given the survey parameters.

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arXiv2026

A FLASH HI absorption search in compact sources in the pilot ASKAP interplanetary scintillation field

In this pilot study, we use data from the First Large Absorption Survey in HI (FLASH) to search for redshifted HI 21cm absorption at $0.4<z<1$ towards 157 bright radio sources with Interplanetary Scintillation (IPS) measurements at 820MHz in a single field observed with the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. The ASKAP IPS measurements, which use only 2.5 minutes of observing time in total, allow us to estimate the compactness of these radio sources on sub-arcsecond scales at a frequency within the 712-1000MHz FLASH band. In particular, the Normalised Scintillation Index (NSI) for each source reflects the fraction of the flux density arising from compact components less than 0.1 arcsec in diameter. We find that $18\pm5$% of ASKAP sources with flux densities above 150mJy are highly compact with NSI $\geq0.8$ - implying that at least 80% of their radio emission arises from a single region smaller than about 800pc in size. The compactness of these sources makes them ideal probes for an HI absorption search, since the covering factor for any HI gas clouds along the line of sight is likely to be high. About half of the sources with NSI $\geq0.8$ also have peaked radio spectral energy distributions (SEDs), consistent with previous IPS studies at lower frequencies. These pilot results imply that IPS measurements with ASKAP can provide a simple and powerful tool for identifying uniform samples of compact radio sources at frequencies of a few hundred MHz across large areas of sky. With FLASH, we detect two new HI absorption lines against compact sources in the $\sim30$deg$^2$ region of sky covered by the IPS data; an associated HI line at redshift $z=0.9540$ (with a matching optical redshift) in MRC 2125-237 (NSI = 0.98), and a likely intervening line at $z=0.4632$ towards MRC 2131-241 (NSI = 0.84).

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arXiv2026

Tracing Cold Gas in Absorption Across Cosmic Time with the SKA

Observing the 21-cm HI line in absorption provides a powerful means of tracing the cold neutral gas in normal and active galaxies across cosmic time. The frequency coverage and sensitivity of SKAO will allow us to detect HI in absorption from z = 0 to beyond z = 6, enabling the characterisation of the properties of cold gas in and around galaxies at all epochs. This chapter summarises recent advances in absorption-line studies, lessons learned from precursor surveys, and updates the science case presented in Kanekar and Briggs (2004) and Morganti et al. (2015), focusing on the capabilities enabled by the SKA design baseline, Array Assembly 4 (AA4). We expand on these earlier works by presenting new opportunities to simultaneously search for OH 18-cm absorption, an efficient tracer of diffuse molecular gas that complements the atomic gas traced by HI absorption, as well as the need for sub-arcsecond scale spectroscopic imaging and multi-wavelength data from large surveys. These advances will allow SKAO absorption surveys to address key questions surrounding the fuelling and feedback cycles of AGN and the evolution of the cold neutral gas across cosmic time.

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arXiv2025

Tracing Gas Kinematics and Interactions between H II Regions and Molecular Clouds using VLA Observations of Recombination Lines and Hydroxyl

Observational studies of HII region-molecular cloud interactions constrain models of feedback and quantify its impact on the surrounding environment. A recent hypothesis proposes that a characteristic spectral signature in ground state hyperfine lines of hydroxyl (OH) -- the OH flip -- may trace gas that is dynamically interacting with an expanding HII region, offering a new means of probing such interactions. We explore this hypothesis using dedicated Jansky Very Large Array (VLA) observations of three Galactic HII regions, G049.205$-$0.343, G034.256+0.145 and G024.471+0.492, in 1--2 GHz continuum emission, all four 18-cm ground-state OH lines, and multiple hydrogen radio recombination lines. A Gaussian decomposition of the molecular gas data reveals complex OH emission and absorption across our targets. We detect the OH flip towards two of our sources, G049.205$-$0.343 and G034.256+0.145, finding agreement between key predictions of flip hypothesis and the observed multi-wavelength spectra, kinematics and morphology. Specifically, we demonstrate a strong spatial and kinematic association between the OH flip and the ionized gas of the HII regions -- the first time this has been demonstrated for resolved sources -- and evidence from $^{13}$CO(1--0) data that the expected OH component originates from the non-disturbed gas of the parent cloud. While we detect no flip in G024.471+0.492, we do find evidence of interacting molecular gas traced by OH, providing further support for OH's ability to trace HII region-molecular cloud interactions.

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arXiv2025

VLBI studies of FLASH H I 21-cm absorbers -- I

We have conducted VLBA 1.4 GHz (L-band) continuum observations towards twelve sources with HI 21-cm absorption detections at redshift $0.4<z<0.7$ in the pilot surveys of FLASH, an ongoing survey with the ASKAP radio telescope. 11 of the 12 targets are resolved in the VLBA observations. Using the parsec scale radio images, we have classified the source morphology and identified the radio core. Six of the twelve targets have core-jet morphology, four have two-sided jet morphology, one has a complex morphology, and one is unresolved. We describe a methodology to test whether the emission from the core or the total emission detected in the VLBA image has sufficient flux density to cause the entire HI 21-cm absorption, and we estimate limits on the gas covering factor and velocity-integrated optical depth (VOD). We find that for seven of the twelve sources, the core has sufficient flux density to cause all the HI 21-cm absorption detected in the ASKAP spectrum. For three other targets, with projected sizes in the range $\rm 305-409 \ pc$, a large fraction of the entire emission in the VLBA map could be occulted by the gas. For 0903+010 (NVSS J090331+010846), we estimate that at least $\approx 73\%$ of the peak absorption detected in the ASKAP spectrum could arise against the emission detected in the VLBA image. For the target 0023+010 (NVSS J002331+010114), we estimate an upper limit on the VOD of $\rm 169 \ km \ s^{-1}$, the highest in our sample. For 0903+010 (NVSS J090331+010846) we estimate a lower limit of $\rm 104 \ km \ s^{-1}$ on the VOD. We find that the distribution of HI 21-cm VODs at $0.4<z<1.0$ could increase by up to a factor of three after correction for the covering factors using our VLBA measurements.

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arXiv2025

The First Large Absorption Survey in HI (FLASH): II. Pilot Survey data release and first results

The First Large Absorption Survey in HI (FLASH) is a large-area radio survey for neutral hydrogen in the redshift range 0.4 1$, and appear to be a mixture of intervening and associated systems. Interestingly, around two-thirds of the lines found in this untargeted sample are detected against sources with a peaked-spectrum radio continuum, which are only a minor (5-20%) fraction of the overall radio-source population. The overall detection rate for HI absorption lines in the Pilot Surveys (0.3 to 0.5 lines per ASKAP field) is a factor of two below the expected value. One possible reason for this is the presence of a range of spectral-line artefacts in the Pilot Survey data that have now been mitigated and are not expected to recur in the full FLASH survey. A future paper will discuss the host galaxies of the HI absorption systems identified here.

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arXiv2025

ALMACAL XIV: X-Shooter Spectroscopy, Infrared Properties and Radio SEDs of Calibrators

The ALMACAL-22 survey includes over 2700 hours of observations of ALMA phase and amplitude calibrators, spanning frequencies from 84 to 950 GHz across bands 3 to 10. In total, 687 out of the 1,047 calibrators have redshifts confirmed with spectroscopy and we find an additional 50 featureless blazars. The redshift distribution of the ALMACAL-22 sample peaks at $z \approx 1$ and spans a wide range, from the nuclei of nearby galaxies at $z \ll 0.01$ to quasars at $z = 3.742$. 70 new VLT/X-Shooter spectra of these sources covering UV to NIR wavelengths are also presented, which will be used in future stacking experiments to search for cold gas in the circumgalactic medium. Infrared magnitudes from WISE indicate that the majority of the sources are consistent with being quasars or blazars. After fitting the radio spectral energy distributions of the calibrators, we find that most ALMA calibrators exhibit peaked spectra or are re-triggered which is surprising given the large number of blazars in the sample. The peak frequencies span three orders of magnitude from 100 MHz to 170 GHz, corresponding to linear sizes ranging from sub-pc to $>$ 10 kpc. In the future, when combined with high-resolution radio imaging, these results will offer valuable constraints on the molecular gas content of the CGM, as well as the ages and duty cycles of AGN jets. The ever-growing ALMACAL data set will remain an indispensable resource for studying the various aspects of galaxy formation and evolution.

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arXiv2024

Why so young? A curious connection between the broadband flux and neutral gas content of AGN

We present here a study of the broadband spectral properties of 33 sources detected in HI absorption as part of the ASKAP-FLASH Pilot Surveys. We outline our approach to spectral classification and discuss the correlation seen between spectral shape and the detection of HI absorption. We further consider the implications of the observed correlation on the spatial distribution of the neutral gas, and on the jet-gas interactions. Our results are evaluated in the context of the forthcoming, full ASKAP-FLASH survey and other large, untargeted searches of the radio sky.

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arXiv2024

A search for HI absorption in distant star-forming galaxies with ASKAP-FLASH -- I. Selection and analysis of the radio sample

We present and discuss two catalogues of UV-selected (NUV $< 22.8$ mag) galaxies that lie within a 200 deg$^2$ area of sky covered by the ASKAP FLASH survey and have an impact parameter of less than 20 arcsec to a FLASH radio continuum source. These catalogues are designed to enable a future search for 21 cm HI absorption in and around star-forming galaxies at redshift $0.4 80 percent) star-forming and resemble the overall WiggleZ population. The ($g - i$) colour evolution with redshift is consistent with a history of active star-formation, but the radio-associated objects are typically redder and have colours similar to high-excitation radio galaxies. The redshift distribution of the two catalogues matches the overall distribution for WiggleZ galaxies, despite their otherwise rare radio properties. These catalogues can be expanded in future as new radio data become available, and a forthcoming paper will present the HI absorption results.

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arXiv2024

Mapping Obscured Star Formation in the Host Galaxy of FRB 20201124A

We present high-resolution 1.5 $-$ 6 GHz Karl G. Jansky Very Large Array (VLA) and Hubble Space Telescope (HST) optical and infrared observations of the extremely active repeating fast radio burst (FRB) FRB 20201124A and its barred spiral host galaxy. We constrain the location and morphology of star formation in the host and search for a persistent radio source (PRS) coincident with FRB 20201124A. We resolve the morphology of the radio emission across all frequency bands and measure a star formation rate SFR $\approx 8.9\,M_{\odot}$ yr$^{-1}$, approximately $\approx 2.5-6$ times larger than optically-inferred SFRs, demonstrating dust-obscured star formation throughout the host. Compared to a sample of all known FRB hosts with radio emission, the host of FRB 20201124A has the most significantly obscured star formation. While HST observations show the FRB to be offset from the bar or spiral arms, the radio emission extends to the FRB location. We propose that the FRB progenitor could have formed in situ (e.g., a magnetar born from a massive star explosion). It is still plausible, although less likely, that the progenitor of FRB 20201124A migrated from the central bar of the host. We further place a limit on the luminosity of a putative PRS at the FRB position of $L_{\rm 6.0 \ GHz}$ $\lesssim$ 1.8 $\times 10^{27}$ erg s$^{-1}$ Hz$^{-1}$, among the deepest PRS luminosity limits to date. However, this limit is still broadly consistent with both magnetar nebulae and hypernebulae models assuming a constant energy injection rate of the magnetar and an age of $\gtrsim 10^{5}$ yr in each model, respectively.

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arXiv2023

The FLASH pilot survey: an HI absorption search against MRC 1-Jy radio sources

We report an ASKAP search for associated HI 21-cm absorption against bright radio sources from the Molonglo Reference Catalogue (MRC) 1-Jy sample. The search uses pilot survey data from the ASKAP First Large Absorption Survey in \hi (FLASH) covering the redshift range $0.42 < z < 1.00$. From a sample of 62 MRC 1-Jy radio galaxies and quasars in this redshift range we report three new detections of associated HI 21-cm absorption, yielding an overall detection fraction of $1.8\%^{+4.0\%}_{-1.5\%}$. The detected systems comprise two radio galaxies (MRC 2216$-$281 at $z=0.657$ and MRC 0531$-$237 at $z=0.851$) and one quasar (MRC 2156$-$245 at $z=0.862$). The MRC 0531$-$237 absorption system is the strongest found to date, with a velocity integrated optical depth of $\rm 143.8 \pm 0.4 \ km \ s^{-1}$. All three objects with detected HI 21-cm absorption are peaked-spectrum or compact steep-spectrum (CSS) radio sources, classified based on our SED fits to the spectra. Two of them show strong interplanetary scintillation at 162 MHz, implying that the radio continuum source is smaller than 1 arcsec in size even at low frequencies. Among the class of peaked-spectrum and compact steep-spectrum radio sources, the HI detection fraction is $23\%^{+22\%}_{-13\%}$. This is consistent within $1σ$ with a detection fraction of $\approx 42\%^{+21\%}_{-15\%}$ in earlier reported GPS and CSS samples at intermediate redshifts ($0.4 < z < 1.0$). All three detections have a high 1.4 GHz radio luminosity, with MRC 0531$-$237 and MRC 2216$-$281 having the highest values in the sample, $\rm > 27.5 \ W \ Hz^{-1}$. The preponderance of extended radio sources in our sample could partially explain the overall low detection fraction, while the effects of a redshift evolution in gas properties and AGN UV luminosity on the neutral gas absorption still need to be investigated.

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arXiv2023

FAST discovery of a fast neutral hydrogen outflow

In this letter, we report the discovery of a fast neutral hydrogen outflow in SDSS J145239.38+062738.0, a merging radio galaxy containing an optical type I active galactic nuclei (AGN). This discovery was made through observations conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) using redshifted 21-cm absorption. The outflow exhibits a blueshifted velocity likely up to $\sim-1000\,\rm km\,s^{-1}$ with respect to the systemic velocity of the host galaxy with an absorption strength of $\sim -0.6\,\rm mJy\,beam^{-1}$ corresponding to an optical depth of 0.002 at $v=-500\,\rm km\,s^{-1}$. The mass outflow rate ranges between $2.8\times10^{-2}$ and $3.6\, \rm M_\odot \, yr^{-1}$, implying an energy outflow rate ranging between $4.2\times10^{39}$ and $9.7\times10^{40}\rm\,erg\,s^{-1}$, assuming 100 K $<T_{\rm s}<$ 1000 K. Plausible drivers of the outflow include the star bursts, the AGN radiation, and the radio jet, the last of which is considered the most likely culprit according to the kinematics. By analysing the properties of the outflow, the AGN, and the jet, we find that if the HI outflow is driven by the AGN radiation, the AGN radiation seems not powerful enough to provide negative feedback whereas the radio jet shows the potential to provide negative feedback. Our observations contribute another example of a fast outflow detected in neutral hydrogen, as well as demonstrate the capability of FAST in detecting such outflows.

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arXiv2023

The unseen host galaxy and high dispersion measure of a precisely-localised Fast Radio Burst suggests a high-redshift origin

FRB 20210912A is a fast radio burst (FRB), detected and localised to sub-arcsecond precision by the Australian Square Kilometre Array Pathfinder. No host galaxy has been identified for this burst despite the high precision of its localisation and deep optical and infrared follow-up, to 5-$σ$ limits of $R=26.7$ mag and $K_\mathrm{s}=24.9$ mag with the Very Large Telescope. The combination of precise radio localisation and deep optical imaging has almost always resulted in the secure identification of a host galaxy, and this is the first case in which the line-of-sight is not obscured by the Galactic disk. The dispersion measure of this burst, $\mathrm{DM_{FRB}}=1233.696\pm0.006~\mathrm{pc}\ \mathrm{cm}^{-3}$, allows for a large source redshift of $z>1$ according to the Macquart relation. It could thus be that the host galaxy is consistent with the known population of FRB hosts, but is too distant to detect in our observations ($z>0.7$ for a host like that of the first repeating FRB source, FRB 20121102A); that it is more nearby with a significant excess in $\mathrm{DM_{host}}$, and thus dimmer than any known FRB host; or, least likely, that the FRB is truly hostless. We consider each possibility, making use of the population of known FRB hosts to frame each scenario. The fact of the missing host has ramifications for the FRB field: even with high-precision localisation and deep follow-up, some FRB hosts may be difficult to detect, with more distant hosts being the less likely to be found. This has implications for FRB cosmology, in which high-redshift detections are valuable.

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arXiv2023

The Host Galaxy of FRB 20171020A Revisited

The putative host galaxy of FRB 20171020A was first identified as ESO 601-G036 in 2018, but as no repeat bursts have been detected, direct confirmation of the host remains elusive. In light of recent developments in the field, we re-examine this host and determine a new association confidence level of 98%. At 37 Mpc, this makes ESO 601-G036 the third closest FRB host galaxy to be identified to date and the closest to host an apparently non-repeating FRB (with an estimated repetition rate limit of < 0.011 bursts per day above 10 erg). Due to its close distance, we are able to perform detailed multi-wavelength analysis on the ESO 601-G036 system. Follow-up observations confirm ESO 601-G036 to be a typical star-forming galaxy with HI and stellar masses of log(M_HI/M_sol) ~ 9.2 and log(M_*/M_sol) = 8.64, and a star formation rate of SFR = 0.09 +/- 0.01 M_sol/yr. We detect, for the first time, a diffuse gaseous tail (log(M_HI/M_sol) ~ 8.3) extending to the south-west that suggests recent interactions, likely with the confirmed nearby companion ESO 601-G037. ESO 601-G037 is a stellar shred located to the south of ESO 601-G036 that has an arc-like morphology, is about an order of magnitude less massive, and has a lower gas metallicity that is indicative of a younger stellar population. The properties of the ESO 601-G036 system indicate an ongoing minor merger event, which is affecting the overall gaseous component of the system and the stars within ESO 601-G037. Such activity is consistent with current FRB progenitor models involving magnetars and the signs of recent interactions in other nearby FRB host galaxies.

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arXiv2023

Does a radio jet drive the massive multi-phase outflow in the ultra-luminous infrared galaxy IRAS 10565+2448?

We present new upgraded Giant Metrewave Radio Telescope (uGMRT) HI 21-cm observations of the ultra-luminous infrared galaxy IRAS 10565+2448, previously reported to show blueshifted, broad, and shallow HI absorption indicating an outflow. Our higher spatial resolution observations have localised this blueshifted outflow, which is $\sim$ 1.36 kpc southwest of the radio centre and has a blueshifted velocity of $\sim 148\,\rm km\,s^{-1}$ and a full width at half maximum (FWHM) of $\sim 581\,\rm km\,s^{-1}$. The spatial extent and kinematic properties of the HI outflow are consistent with the previously detected cold molecular outflows in IRAS 10565+2448, suggesting that they likely have the same driving mechanism and are tracing the same outflow. By combining the multi-phase gas observations, we estimate a total outflowing mass rate of at least $140\, \rm M_\odot \,yr^{-1}$ and a total energy loss rate of at least $8.9\times10^{42}\,\rm erg\,s^{-1}$, where the contribution from the ionised outflow is negligible, emphasising the importance of including both cold neutral and molecular gas when quantifying the impact of outflows. We present evidence of the presence of a radio jet and argue that this may play a role in driving the observed outflows. The modest radio luminosity $L_{\rm1.4GHz}$ $\sim1.3\times10^{23}\,{\rm W\,Hz^{-1}}$ of the jet in IRAS 10565+2448 implies that the jet contribution to driving outflows should not be ignored in low radio luminosity AGN.

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arXiv2022

FLASH Pilot Survey: Detections of associated 21 cm HI absorption in GAMA galaxies at 0.42 < z <1.00

We present the results of a search for associated 21 cm HI absorption at redshift 0.42 < z < 1.00 in radio-loud galaxies from three Galaxy And Mass Assembly (GAMA) survey fields. These observations were carried out as part of a pilot survey for the ASKAP First Large Absorption Survey in HI (FLASH). From a sample of 326 radio sources with 855.5 MHz peak flux density above 10 mJy we detected two associated HI absorption systems, in SDSS J090331+010847 at z= 0.522 and SDSS J113622+004852 at z= 0.563. Both galaxies are massive (stellar mass > 10$^{11}$ M$_{sun}$) and have optical spectra characteristic of luminous red galaxies,though SED fitting implies that SDSS J113622+004852 contains a dust-obscured starburst with SFR ~ 69 M$_{sun}$ yr$^{-1}$. The HI absorption lines have a high optical depth, with $τ_{pk}$ of 1.77 $\pm$ 0.16 for SDSS J090331+010847 (the highest value for any z > 0.1 associated system found to date) and 0.14 $\pm$ 0.01 for SDSS J113622+004852. In the redshift range probed by our ASKAP observations, the detection rate for associated HI absorption lines (with $τ_{pk}$ > 0.1 and at least 3$σ$ significance) is 2.9 (+9.7 -2.6) percent. Although the current sample is small, this rate is consistent with a trend seen in other studies for a lower detection rate of associated 21 cm HI absorption systems at higher redshift. We also searched for OH absorption lines at 0.67 < z < 1.34, but no detection was made in the 145 radio sources searched.

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arXiv2022

Observations of cold extragalactic gas clouds at $z = 0.45$ towards PKS 1610-771

We present results from MUSE observations of a 21-cm HI absorption system detected with the Australian Square Kilometre Array Pathfinder radio telescope at redshift $z = 0.4503$ towards the $z = 1.71$ quasar PKS 1610-771. We identify four galaxies (A, B, X and Y) at the same redshift as the 21-cm H I Damped Lyman-α (DLA) absorption system, with impact parameters ranging from less than 10 kpc to almost 200 kpc from the quasar sightline. Ca II and Na I absorption is seen in the MUSE spectrum of the background QSO, with velocities coinciding with the initial HI 21-cm detection, but tracing less dense and warmer gas. This metal-line component aligns with the rotating ionised disc of galaxy B (impact parameter 18 kpc from the QSO) and appears to be co-rotating with the galaxy disc. In contrast, the 21-cm HI absorber is blueshifted relative to the galaxies nearest the absorber and has the opposite sign to the velocity field of galaxy B. Since galaxies A and B are separated by only 17 kpc on the sky and $70$ km s$^{-1}$ in velocity, it appears likely that the 21-cm detection traces extragalactic clouds of gas formed from their interaction. This system reveals that the cold 100 K neutral gas critical for star formation can be associated with complex structures beyond the galaxy disc, and is a first case study made in preparation for future large 21-cm absorption surveys like the ASKAP First Large Absorption Survey in HI.

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arXiv2021

Characterizing the FRB host galaxy population and its connection to transients in the local and extragalactic Universe

We present the localization and host galaxies of one repeating and two apparently non-repeating Fast Radio Bursts. FRB20180301A was detected and localized with the Karl G. Jansky Very Large Array to a star-forming galaxy at $z=0.3304$. FRB20191228A, and FRB20200906A were detected and localized by the Australian Square Kilometre Array Pathfinder to host galaxies at $z=0.2430$ and $z=0.3688$, respectively. We combine these with 13 other well-localized FRBs in the literature, and analyze the host galaxy properties. We find no significant differences in the host properties of repeating and apparently non-repeating FRBs. FRB hosts are moderately star-forming, with masses slightly offset from the star-forming main-sequence. Star formation and low-ionization nuclear emission-line region (LINER) emission are major sources of ionization in FRB host galaxies, with the former dominant in repeating FRB hosts. FRB hosts do not track stellar mass and star formation as seen in field galaxies (more than 95% confidence). FRBs are rare in massive red galaxies, suggesting that progenitor formation channels are not solely dominated by delayed channels which lag star formation by Gigayears. The global properties of FRB hosts are indistinguishable from core-collapse supernovae (CCSNe) and short gamma-ray bursts (SGRBs) hosts, and the spatial offset (from galaxy centers) of FRBs is mostly inconsistent with that of the Galactic neutron star population (95% confidence). The spatial offsets of FRBs (normalized to the galaxy effective radius) also differ from those of globular clusters (GCs) in late- and early-type galaxies with 95% confidence.

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