arXiv subjects

Biny Sebastian

Publications and source records attributed to Biny Sebastian.

At least 19 recordsLinked to original sources

arXiv2025

What drives kpc-scale outflows in Radio-Quiet AGN? Insights from a Polarimetric Study

We present a review of our findings on the origin, drivers, nature, and impact of kiloparsec-scale radio emission in radio-quiet (RQ) AGN. Using radio polarimetric techniques, we probe the dynamics and magnetic (B-) field geometry of outflows in Seyfert and LINER galaxies. Multi-band data from the Karl G. Jansky Very Large Array (VLA) reveal how low-power jets interact with their environment. These interactions can slow down and disrupt the radio outflows while locally regulating star formation through AGN feedback. Several radio properties correlate strongly with the black hole mass, similar to trends observed in radio-loud (RL) AGN. Although their characteristics differ, RQ systems might not be intrinsically distinct from RL AGN, apart from lower jet powers. Our polarization measurements further suggest a composite model in which a black hole-accretion disk system drives both a collimated jet with a small-pitch-angle helical B-field and a wide-angle wind threaded by a high-pitch-angle helical field.

astro-ph.GA↗

arXiv2025

SDSO1 is a Shocked Ghost Planetary Nebula in Front of M 31

We present new, deep narrowband imagery and discuss the nature of SDSO 1, the large [O III]-emitting nebula centered 1.5 degrees SE of M 31. We find strong evidence to support the hypothesis that SDSO 1 is unrelated to M 31 and is instead a faded, giant (D = 20 pc), ghost planetary nebula (GPN) expelled by the symbiotic WD binary star EG Andromedae. The associated 45-pc long turbulent tail, seen in projection in front of M 31, yields an estimated age of 400 kyr. The initial hypersonic velocity of 91 km/s drives a strong bow shock into the local interstellar medium and a reverse shock into the GPN. The SDSO 1 GPN has reached the terminal phase in its evolution where its outward expansion and forward motion have been decelerated greatly by ram pressure and the [O III] emission arises primarily from the reverse shock. We establish the shock-powered GPN phase as a new phase of planetary nebula (PN) evolution, and identify 24 candidate GPNe by their large size and shock-tail morphology. This includes several giant halos of younger PNe, possibly expelled by now degenerate binary companions. The interaction of an old, fast-moving GPN with the ISM generates shocks that remain visible long after the photoionized PN shell has faded below the limit of detectability.

astro-ph.GA↗

arXiv2025

Jet-mode feedback in NGC 5972: insights from resolved MUSE, GMRT and VLA observations

NGC 5972, a Voorwerp galaxy, features a helical-shaped extended emission-line region (EELR) with a radius > 10 kpc and a S-shaped radio structure spanning about 470 kpc. We use VLT MUSE, GMRT, and VLA to study the stellar and ionized gas kinematics and how the radio jet influences the gas in the galaxy. Our sensitive radio observations detect the southern jet for the first time, roughly coinciding with the southern EELR. The VLA images show a continuous inner jet connected to the outer E-W lobe, confirming the jet origin of the radio emission. Our kinematic analysis shows spatial correlations between the radio jet and the outflowing gas, supporting the jet-driven feedback mechanism. More interestingly, we observe enhanced velocity dispersion in the perpendicular direction along with a shell-like structure. Our BPT analysis shows that the [O III] emission overlapping with the radio jet is consistent with the shock+precursor model, whereas in the perpendicular region, a pure shock model fits well with the observations, indicating jet-induced shocks. Radio observations indicate episodic AGN activity characterized by surface brightness and spectral index discontinuities. Overall, based on our findings, we propose a jet-driven feedback mechanism as one of the key factors in the formation of the EELR in NGC 5972. Future high-resolution radio observations will be crucial to further investigate the origin of the EELR and quantify the extent to which the jet influences its formation and evolution.

astro-ph.GA↗

arXiv2025

Radio Spectral Energy Distribution of Low-$z$ Metal Poor Extreme Starburst Galaxies: Novel insights on the escape of ionizing photons

Recent optical surveys have identified a rare population of low-$z$ ($z \sim 0.01 - 0.06$) extreme star-forming galaxies (xSFGs) characterized by very low metallicity, strong emission lines, extremely high specific star-formation rate, low stellar mass, and strong Ly~$\alpha$ emission. Their global properties resemble recently discovered $z > 6$ reionization-era star-forming galaxies. We present new multi-frequency radio continuum (RC) observations of $8$ xSFGs using the upgraded Giant Metrewave Radio Telescope (uGMRT) at $1.25$ GHz, the Karl G. Jansky Very Large Array (VLA) at $1.5, 3.0, 6.0, 10.0$ and $15.0$ GHz, along with archival LOw Frequency ARray (LOFAR) data at $150$ MHz for several sources. These data allow construction of the radio spectral energy distribution (radio-SED) from $\sim 1$ GHz (down to $150$ MHz for some sources) to $15$ GHz, spanning nearly two orders of magnitude in frequency. We find that xSFGs exhibit a flat spectral index between $6$ and $15$ GHz, while a subset shows spectral turnovers at $0.3 - 3$ GHz. Our Bayesian radio-SED modeling indicates that these features are consistent with a high thermal fraction combined with free-free absorption, requiring high emission measures in some systems. By comparing modeled thermal radio emission with observed H$\beta$ line flux density, we find evidence for dust in several xSFGs. Finally, we confirm a previously reported correlation between Lyman continuum escape fraction, ionization state, and radio spectral index, particularly among strong leakers.

astro-ph.GA↗

arXiv2024

HI Imaging of a Blueberry Galaxy Suggests a Merger Origin

Blueberry galaxies (BBs) are fainter, less massive, and lower redshift counterparts of the Green pea galaxies. They are thought to be the nearest analogues of the high redshift Lyman Alpha (Ly$\alpha$) emitters. We report the interferometric imaging of HI 21 cm emission from a Blueberry galaxy, J1509+3731, at redshift, z = 0.03259, using the Giant Metrewave Radio Telescope (GMRT). We find that this Blueberry galaxy has an HI mass of $M_{\text{HI}} \approx 3\times 10^8 \, M_{\odot}$ and an HI-to-stellar mass ratio $M_{\text{HI}}/M_* \approx$ 2.4. Using SFR estimates from the H$\beta$ emission line, we find that it has a short HI depletion time scale of $\approx 0.2$ Gyr, which indicates a significantly higher star-formation efficiency compared to typical star-forming galaxies at the present epoch. Interestingly, we find an offset of $\approx 2$ kpc between the peak of the HI 21 cm emission and the optical centre which suggests a merger event in the past. Our study highlights the important role of mergers in triggering the starburst in BBs and their role in the possible leakage of Lyman-$\alpha$ and Lyman-continuum photons which is consistent with the previous studies on BB galaxies.

astro-ph.GA↗

arXiv2024

A VLBA-uGMRT search for candidate binary black holes: Study of six X-shaped radio galaxies with double-peaked emission lines

Identifying methods to discover dual AGN has proven to be challenging. Several indirect tracers have been explored in the literature, including X/S-shaped radio morphologies and double-peaked (DP) emission lines in the optical spectra. However, the detection rates of confirmed dual AGN candidates from the individual methods remain extremely small. We search for binary black holes in a sample of six sources that exhibit both X-shaped radio morphology and DP emission lines using the VLBA. Three out of the six sources show dual VLBA compact components, making them strong candidates for binary black hole sources. In addition, we present deep uGMRT images revealing the exquisite details of the X-shaped wings in three sources. We present a detailed precession modeling analysis of these sources. The BH separations estimated from the simplistic geodetic precession model are incompatible with those estimated from emission line offsets and the VLBA separations. However, precession induced by a noncoplanar secondary black hole is a feasible mechanism for explaining the observed X-shaped radio morphologies and the black hole separations estimated from other methods. The black hole separations estimated from the double-peaked emission lines agree well with the VLBA compact component separations. Future multi-frequency VLBA observations will be critical in ruling out or confirming the binary black hole scenario in the three galaxies with dual component detections.

astro-ph.GA↗

arXiv2023

Low-redshift Lyman Continuum Survey: Radio continuum properties of low-$z$ Lyman continuum emitters

Sources that leak Lyman-continuum (LyC) photons and lead to the reionisation of the universe are intensely studied using multiple observing facilities. Recently, the Low-redshift LyC Survey (LzLCS) has found the first large sample of LyC emitting galaxies at low redshift ($z\sim 0.3$) with the Hubble Space Telescope/Cosmic Origins Spectrograph. The LzLCS sample contains a robust estimate of the LyC escape fraction ($f_\mathrm{esc}^\mathrm{LyC}$) for 66 galaxies spanning a wide range of $f_\mathrm{esc}^\mathrm{LyC}$. Here we, for the first time, aim to study the radio continuum (RC) properties of LzLCS sources and their dependence on $f_\mathrm{esc}^\mathrm{LyC}$. We present Karl G. Jansky Very Large Array RC observations at C (4-8 GHz), S (2-4 GHz) and L (1-2 GHz) bands for a sub-sample of the LzLCS sources. The radio spectral index ($\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$) spans a wide range from being flat ( $\geq -0.1$) to very steep ($\leq -1.0$). The strongest leakers in our sample show flat $\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$, weak leakers have $\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$ close to normal star-forming galaxies, and non-leakers are characterized by steep $\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$. We argue that a combination of young ages, free-free absorption, and a flat cosmic-ray energy spectrum can altogether lead to a flat $\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$ for strong leakers. Non-leakers are characterized by steep spectra which can arise due to break/cutoff at high frequencies. Such a cutoff in the spectrum can arise in a single injection model of CRs characteristic of galaxies which have recently stopped star formation. Such a relation between $\alpha^{\mathrm{3GHz}}_\mathrm{6GHz}$ and $f_\mathrm{esc}^\mathrm{LyC}$ hints at the interesting role of supernovae, CRs, and magnetic fields in facilitating the escape ( and/or the lack) of LyC photons. (Abridged)

astro-ph.GA↗

arXiv2023

New Black Hole Spin Values for Sagittarius A* Obtained with the Outflow Method

Six archival Chandra observations are matched with eight sets of radio data and studied in the context of the outflow method to measure and study the spin properties of $\rm{Sgr ~A^*}$. Three radio and X-ray data sets obtained simultaneously, or partially simultaneously, are identified as preferred for the purpose of measuring the spin properties of $\rm{Sgr ~A^*}$. Similar results are obtained with other data sets. Results obtained with the preferred data sets are combined and indicate a weighted mean value of the spin function of $\rm{F} = 0.62 \pm 0.10$ and dimensionless spin angular momentum of $\rm{a_*} = 0.90 \pm 0.06$. The spin function translates into measurements of the black hole rotational mass, $\rm{M_{rot}}$, irreducible mass, $\rm{M_{irr}}$, and spin mass-energy available for extraction, $\rm{M_{spin}}$, relative to the total black hole dynamical mass, $\rm{M_{dyn}}$. Weighted mean values of $\rm{(M_{rot}/M_{dyn}) = (0.53 \pm 0.06)}$, $\rm{({M_{irr}/M_{dyn})} = (0.85 \pm 0.04)}$, $\rm{({M_{spin}/M_{dyn})} = (0.15 \pm 0.04)}$, $\rm{{M_{rot}} = (2.2 \pm 0.3) \times 10^6 ~M_{\odot}}$, $\rm{{M_{irr}} = (3.5 \pm 0.2) \times 10^6 ~M_{\odot}}$, and $\rm{{M_{spin}} = (6.2 \pm 1.6) \times 10^5 ~M_{\odot}}$ are obtained; of course $\rm{{(M_{rot}/M_{irr})} = (0.62 \pm 0.10)}$ since $\rm{{(M_{rot}/M_{irr})} = F}$. Values obtained for $\rm{Sgr ~A^*}$ are compared with those obtained for M87 based on the published spin function which indicate that M87 carries substantially more rotational energy and spin mass-energy relative to the total (i.e., dynamical) black hole mass, the irreducible black hole mass, and in absolute terms.

astro-ph.GA↗

arXiv2023

A detailed study of the polarisation convention of the Giant Metrewave Radio Telescope

Our work aims to investigate the polarisation convention of the Giant Metrewave Radio Telescope (GMRT) radio telescope and understand whether the telescope follows the standard IAU/IEEE convention. The GMRT antennas are prime focus antennas, i.e. the radiation falling on the antenna feed reverses its circular polarisation. If this reflection is not taken into account, it will result in a reversal of circular polarisation. We carried out several tests to understand the GMRT polarisation convention. The observations were carried out on several strong and highly polarised pulsars with known polarisation properties at GMRT wavelengths, mainly covering frequency bands 2, 3 and 4. In addition, we tracked the signal from the feed to the fibre optic system, and fibre optic system to the user end. We also tracked satellites of known polarisations as well as utilised right and left circularly polarised helical antennas to study the polarisation convention. Our study shows that the GMRT channels 1 and 2 are true R and L, however, GMRT being a prime focus instrument, the reflection due to the dish reverses the sense of polarisation and converts the right circular polarisation (RCP) into left circular polarisation (LCP) and vice versa. This has not been taken into account and thus the GMRT Stokes V and U signs need to be reversed to make them consistent with the IAU/IEEE convention. This objective can be achieved by reassigning channel 1 to L and channel 2 to R for all circular feeds, i.e. bands 2, 3, and 4. The study remains inconclusive for the GMRT band 5, which has linear feeds.

astro-ph.IM↗

arXiv2023

AGN Feedback Through Multiple Jet Cycles in the Seyfert Galaxy NGC 2639

The Seyfert galaxy NGC 2639 was known to exhibit three episodes of AGN jet/lobe activity. We present here the upgraded Giant Metrewave Radio Telescope (uGMRT) 735 MHz image of NGC 2639 showing a fourth episode as witnessed by the discovery of $\sim9$ kpc radio lobes misaligned with the previously known $\sim1.5$ kpc, $\sim360$ parsec, and $\sim3$ parsec jet features detected through the Karl G. Jansky Very Large Array (VLA) and the Very Long Baseline Array (VLBA), respectively. Using the spectral ageing software BRATS, we derive the ages of the $\sim9$ kpc, $\sim1.5$ kpc, and $\sim360$ parsec episodes to be, respectively, $34^{+4}_{-6}$ Myr, $11.8^{+1.7}_{-1.4}$ Myr, and $2.8^{+0.7}_{-0.5}$ Myr, and conclude that minor mergers occurred $9-22$ Myr apart. NGC 2639 shows a deficit of molecular gas in its central $\sim6$ kpc region. The GALEX NUV image also shows a deficiency of recent star-formation in the same region, while the star formation rate (SFR) surface density in NGC 2639 is lower by a factor of $5-18$ compared to the global Schmidt law of star-forming galaxies. This makes NGC 2639 a rare case of a Seyfert galaxy showing episodic jet activity and possible signatures of jet-driven AGN feedback.

astro-ph.GA↗

arXiv2022

Investigating the origin of X-ray jets: A case study of four hybrid morphology MOJAVE blazars

We have carried out Chandra, HST, and VLA observations of four MOJAVE blazars that have been previously classified as 'hybrid' (FR I/II) blazars in terms of radio morphology but not total radio power. The motivation of this study is to determine the X-ray emission mechanism in jets, these being different in FR I and FR II jets. We detected X-ray jet emission with sufficient SNR in two blazars viz. PKS 0215+015 and TXS 0730+504. We carried out spectral energy distribution (SED) modeling of the broad-band emission from the jet regions in these sources and found that a single synchrotron emission model is ruled out due to the deep upper limits obtained from HST optical and IR data. The IC- CMB model can reproduce the X-ray jet emission in both sources although the model requires extreme jet parameters. Both our sources possess FR II like radio powers and our results are consistent with previous studies suggesting that radio power is more important than FR morphology in determining the emission mechanism of X-ray jets.

astro-ph.GA↗

arXiv2022

The contribution of non-central radio galaxies to AGN feedback in rich galaxy clusters

We present a combined radio/X-ray study of six massive galaxy clusters, aimed at determining the potential for heating of the intra-cluster medium (ICM) by non-central radio galaxies. Since X-ray cavities associated with the radio lobes of non-central galaxies are generally not detectable, we use Giant Metrewave Radio Telescope 610~MHz observations to identify jet sources and estimate their size, and Chandra data to estimate the pressure of the surrounding ICM. In the radio, we detect 4.5% of galaxies above the spectroscopic survey limit (M*K+2.0) of the Arizona cluster redshift survey (ACReS) which covers five of our six clusters. Approximately one tenth of these are extended radio sources. Using star formation (SF) rates determined from mid-infrared data, we estimate the expected contribution to radio luminosity from the stellar population of each galaxy, and find that most of the unresolved or poorly-resolved radio sources are likely star formation dominated. The relatively low frequency and good spatial resolution of our radio data allows us to trace star formation emission down to galaxies of stellar mass ~10^9.5 Msol. We estimate the enthalpy of the (AGN dominated) jet/lobe and tailed sources, and place limits on the energy available from unresolved radio jets. We find jet powers in the range ~10^43-10^46 erg/s, comparable to those of brightest cluster galaxies. Our results suggest that while cluster-central sources are the dominant factor balancing ICM cooling over the long term, non-central sources may have a significant impact, and that further investigation is possible and warranted.

astro-ph.CO↗

arXiv2021

A detailed study of X-ray cavities in the intracluster environment of the cool core cluster Abell 3017

We present a detailed analysis of a cool-core galaxy cluster Abell 3017, at a redshift of z=0.219, which has been identified to be merging with its companion cluster Abell 3016. This study has made use of X-ray Chandra, UV (GALEX), optical (ESO/VLT), mid-infrared (WISE), and radio uGMRT observations of this cluster. Using various image processing techniques, such as unsharp masking, 2-d fits using Beta models, contour binning and the use of surface brightness profiles, we show the existence of a pair of X-ray cavities, at a projected distance of $\sim$20'' (70 kpc) and $\sim$16'' (57 kpc), respectively from the core of Abell~3017. We also detect an excess of X-ray emission located at 25'' $\sim$(88 kpc) south of the centre of Abell 3017, is likely due to the bulk motions in the ICM either by gas sloshing or ram-pressure striping due to a merger. We find that the radio lobes are responsible for the observed X-ray cavities detected in this system. The lower values of the mid-IR WISE colour [W1-W2] and [W2-W3] imply that the central BCG of Abell~3017 is a star-forming galaxy. The current star formation rate of the central BCG, estimated from the ${\rm H\alpha}$ and GALEX FUV luminosities, are equal to be $\sim 5.06\pm 0.78$ Msun yr$^{-1}$ and $\sim 9.20\pm 0.81$ Msun yr$^{-1}$, respectively. We detect, for the first time, a radio phoenix $\sim$150 kpc away from the radio core, with a spectral index of ($\alpha \!\leq\! -1.8$). We also report the detection of $\rm~Pa_\alpha$ emission in this cluster using ESO VLT SINFONI imaging data.

astro-ph.CO↗

arXiv2020

A Radio Polarimetric Study to Disentangle AGN Activity and Star-Formation in Seyfert Galaxies

To understand the origin of radio emission in radio-quiet AGN and differentiate between the contributions from star formation, AGN accretion, and jets, we have observed a nearby sample of Seyfert galaxies along with a comparison sample of starburst galaxies using the EVLA in full-polarization mode in the B-array configuration. The radio morphologies of the Seyfert galaxies show lobe/bubble-like features or prominent cores in radio emission whereas the starburst galaxies show radio emission spatially coincident with the star-forming regions seen in optical images. There is tentative evidence that Seyferts tend to show more polarized structures than starburst galaxies at the resolution of our observations. We find that unlike a sample of Seyfert galaxies hosting kilo-parsec scale radio (KSR) emission, starburst galaxies with superwinds do not show radio-excess compared to the radio-FIR correlation. This suggests that shock acceleration is not adequate to explain the excess radio emission seen in Seyferts and hence most likely have a jet-related origin. We also find that the [O III] luminosity of the Seyferts is correlated with the off-nuclear radio emission from the lobes, whereas it is not well correlated with the total emission which also includes the core. This suggests strong jet-medium interaction, which in turn limits the jet/lobe extents in Seyferts. We find that the power contribution of AGN jet, AGN accretion, and star formation is more or less comparable in our sample of Seyfert galaxies. We also find indications of episodic AGN activity in many of our Seyfert galaxies.

astro-ph.GA↗

arXiv2020

High-resolution VLA low radio frequency observations of the Perseus cluster: radio lobes, mini-halo and bent-jet radio galaxies

We present the first high-resolution 230-470 MHz map of the Perseus cluster obtained with the Karl G. Jansky Very Large Array. The high dynamic range and resolution achieved has allowed the identification of previously-unknown structures in this nearby galaxy cluster. New hints of sub-structures appear in the inner radio lobes of the brightest cluster galaxy NGC 1275. The spurs of radio emission extending into the outer X-ray cavities, inflated by past nuclear outbursts, are seen for the first time at these frequencies, consistent with spectral aging. Beyond NGC 1275, we also analyze complex radio sources harbored in the cluster. Two new distinct, narrowly-collimated jets are visible in IC 310, consistent with a highly-projected narrow-angle tail radio galaxy infalling into the cluster. We show how this is in agreement with its blazar-like behavior, implying that blazars and bent-jet radio galaxies are not mutually exclusive. We report the presence of filamentary structures across the entire tail of NGC 1265, including two new pairs of long filaments in the faintest bent extension of the tail. Such filaments have been seen in other cluster radio sources such as relics and radio lobes, indicating that there may be a fundamental connection between all these radio structures. We resolve the very narrow and straight tail of CR 15 without indication of double jets, so that the interpretation of such head-tail sources is yet unclear. Finally, we note that only the brightest western parts of the mini-halo remain, near NGC 1272 and its bent double jets.

astro-ph.GA↗

arXiv2019

Understanding the Origin of Radio Outflows in Seyfert Galaxies using Radio Polarimetry

The role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5~GHz. Polarization is clearly detected in three Seyfert galaxies and one starburst galaxy. The Seyfert galaxy NGC\,2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC\,3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

astro-ph.GA↗

arXiv2019

The Discovery of Secondary Lobes in the Seyfert Galaxy NGC 2639

We report the discovery of a secondary pair of radio lobes in the Seyfert galaxy NGC 2639 with polarization-sensitive observations with the Karl G. Jansky Very Large Array (VLA). The presence of these lobes, which are aligned nearly perpendicular to the known set of radio lobes observed in the east-west direction, has not been reported previously in the literature. The in-band rotation measure image shows gradients in both the lobes indicative of organised magnetic field structures on kpc-scales. The magnetic field structure is aligned with the jet/lobe direction in both the lobes. Based on the settled optical morphology of the host galaxy, it is likely that a minor merger that did not disrupt the host galaxy structure is responsible for the observed features in NGC 2639. This also explains the near 90$^o$ change in the jet direction; the current jet direction being the result of a new accretion disk formed by the minor merger, whose direction was a result of the angular momentum of the inflowing merger gas.

astro-ph.GA↗

arXiv2019

Radio continuum emission from local analogs of high-z faint LAEs: Blueberry galaxies

We present a radio continuum study of a population of extremely young and starburst galaxies, termed as blueberries at ${\sim}$ 1 GHz using the upgraded Giant Metrewave Radio Telescope (uGMRT). We find that their radio-based star formation rate (SFR) is suppressed by a factor of ${\sim}$ 3.4 compared to the SFR based on optical emission lines. This might be due to (i) the young ages of these galaxies as a result of which a stable equilibrium via feedback from supernovae has not yet been established (ii) escape of cosmic ray electrons via diffusion or galactic scale outflows. The estimated non-thermal fraction in these galaxies has a median value of ${\sim}$0.49, which is relatively lower than that in normal star-forming galaxies at such low frequencies. Their inferred equipartition magnetic field has a median value of 27 ${\mu}$G, which is higher than those in more evolved systems like spiral galaxies. Such high magnetic fields suggest that small-scale dynamo rather than large-scale dynamo mechanisms might be playing a major role in amplifying magnetic fields in these galaxies.

astro-ph.GA↗