Parent Galaxy Research Articles

A comparative high-resolution spectroscopic analysis of in situ and accreted globular clusters

Globular clusters (GCs) are extremely intriguing systems that help in reconstructing the assembly of the Milky Way via the characterisation of their chemo-chrono-dynamical properties. In this study, we use high-resolution spectroscopic archival data from UVES and UVES-FLAMES at the VLT to compare the chemistry of GCs dynamically tagged as either Galactic (NGC 6218, NGC 6522, and NGC 6626) or accreted from distinct merger events (NGC 362 and NGC 1261 from Gaia -Sausage-Enceladus, and Ruprecht 106 from the Helmi Streams) in the metallicity regime where abundance patterns of field stars with different origin effectively separate $( -1.3 We find remarkable similarities in the abundances of the two Gaia -Sausage-Enceladus GCs across all chemical elements. They both display depletion in the alpha -elements (Mg, Si and Ca) and statistically significant differences in Zn and Eu compared to in situ GCs. Additionally, we confirm that Ruprecht 106 exhibits a completely different chemical makeup from the other target clusters, being underabundant in all chemical elements. This demonstrates that when high precision is achieved, the abundances of certain chemical elements can not only efficiently separate in situ from accreted GCs, but can also distinguish among GCs born in different progenitor galaxies. In the end, we investigate the possible origin of the chemical peculiarity of Ruprecht 106. Given that its abundances do not match the chemical patterns of the field stars associated with its most likely parent galaxy (i.e. the Helmi Streams), being depleted in the abundances of alpha -elements in particular, we believe Ruprecht 106 to originate from a less massive galaxy compared to the progenitor of the Helmi Streams.

Evolution of Star Clusters within Galaxies Using Self-consistent Hybrid Hydro/N-body Simulations

We introduce a GPU-accelerated hybrid hydro/N-body code (Enzo-N) designed to address the challenges of concurrently simulating star clusters and their parent galaxies. This task has been exceedingly challenging, primarily due to the considerable computational time required, which stems from the substantial scale difference between galaxies (∼0.1 Mpc) and star clusters (∼parsecs). Yet, this significant scale separation means that particles within star clusters perceive those outside the star cluster in a semistationary state. By leveraging this aspect, we integrate a direct N-body code (Nbody6++GPU) into a cosmological (magneto)hydrodynamic code (Enzo) through utilization of the semistationary background acceleration approximation. We solve the dynamics of particles within star clusters using a direct N-body solver with regularization for few-body interactions, while evolving particles outside—dark matter, gas, and stars—using a particle-mesh gravity solver and hydrodynamic methods. We demonstrate that Enzo-N successfully simulates the coevolution of star clusters and their parent galaxies, capturing phenomena such as core collapse of the star cluster and tidal stripping due to galactic tides. This comprehensive framework opens up new possibilities for studying the evolution of star clusters within galaxies, offering insights that were previously inaccessible.

Detection and characterization of detached tidal dwarf galaxies

Tidal interactions between galaxies often give rise to tidal tails, which can harbor concentrations of stars and interstellar gas resembling dwarf galaxies. Some of these tidal dwarf galaxies (TDGs) have the potential to detach from their parent galaxies and become independent entities, but their long-term survival is uncertain. In this study, we conducted a search for detached TDGs associated with a sample of 39 interacting galaxy pairs in the local Universe using infrared, ultraviolet, and optical images. We employed IR colors and UV/optical/IR spectral energy distributions to identify potential interlopers, such as foreground stars or background quasars. Through spectroscopic observations using the Boller and Chivens spectrograph at San Pedro Mártir Observatory, we confirmed that six candidate TDGs are at the same redshift as their putative parent galaxy pairs. We identified and measured emission lines in the optical spectra and calculated nebular oxygen abundances, which range from log(O/H) = 8.10 ± 0.01 to 8.51 ± 0.02. We have serendipitously discovered an additional detached TDG candidate in Arp72 using available spectra from SDSS. Utilizing the photometric data and the CIGALE code for stellar population and dust emission fitting, we derived the stellar masses, stellar population ages, and stellar metallicities for these detached TDGs. Compared to standard mass-metallicity relations for dwarf galaxies, five of the seven candidates have higher than expected metallicities, confirming their tidal origins. One of the seven candidates remains unclear due to large uncertainties in metallicity, and another has stellar and nebular metallicities compatible with those of a preexisting dwarf galaxy. The latter object is relatively compact in the optical relative to its stellar mass, in contrast to the other candidate TDGs, which have large diameters for their stellar masses compared to most dwarf galaxies. The derived stellar population ages range from 100 Myr to 900 Myr, while the inferred stellar masses are between 2 × 106 M⊙ and 8 × 107 M⊙. Four of the six TDGs are associated with the gas-rich M51-like pair Arp 72, one TDG is associated with a second M51-like pair Arp 86, and another is associated with Arp 65, an approximately equal mass pair. In spite of the relatively low stellar masses of these TDGs, they have survived for at least 100–900 Myrs, suggesting that they are stable and in dynamical equilibrium. We conclude that encounters with a relatively low-mass companion (1/10th–1/4th of the mass of the primary) can also produce long-lasting TDGs.

PHANGS-HST Catalogs for ∼100,000 Star Clusters and Compact Associations in 38 Galaxies. I. Observed Properties

We present the largest catalog to date of star clusters and compact associations in nearby galaxies. We have performed a V-band-selected census of clusters across the 38 spiral galaxies of the PHANGS–Hubble Space Telescope (HST) Treasury Survey, and measured integrated, aperture-corrected near-ultraviolet-U-B-V-I photometry. This work has resulted in uniform catalogs that contain ∼20,000 clusters and compact associations, which have passed human inspection and morphological classification, and a larger sample of ∼100,000 classified by neural network models. Here, we report on the observed properties of these samples, and demonstrate that tremendous insight can be gained from just the observed properties of clusters, even in the absence of their transformation into physical quantities. In particular, we show the utility of the UBVI color–color diagram, and the three principal features revealed by the PHANGS-HST cluster sample: the young cluster locus, the middle-age plume, and the old globular cluster clump. We present an atlas of maps of the 2D spatial distribution of clusters and compact associations in the context of the molecular clouds from PHANGS–Atacama Large Millimeter/submillimeter Array. We explore new ways of understanding this large data set in a multiscale context by bringing together once-separate techniques for the characterization of clusters (color–color diagrams and spatial distributions) and their parent galaxies (galaxy morphology and location relative to the galaxy main sequence). A companion paper presents the physical properties: ages, masses, and dust reddenings derived using improved spectral energy distribution fitting techniques.

Elucidating galaxy population properties using a model-free analysis of quadruply imaged quasar lenses from large surveys

ABSTRACT The population of strong lensing galaxies is a subset of intermediate-redshift massive galaxies, whose population-level properties are not yet well understood. In the near future, thousands of multiply imaged systems are expected to be discovered by wide-field surveys like Rubin Observatory’s Legacy Survey of Space and Time and Euclid. With the soon-to-be robust population of quadruply lensed quasars, or quads, in mind, we introduce a novel technique to elucidate the empirical distribution of the galaxy population properties. Our re-imagining of the prevailing strong lensing analysis does not fit mass models to individual lenses, but instead starts with parametric models of many galaxy populations, which include generally ignored mass distribution complexities and exclude external shear for now. We construct many mock galaxy populations with different properties and obtain populations of quads from each of them. The mock ‘observed’ population of quads is then compared to those from the mocks using a model-free analysis based on a three-dimensional subspace of directly observable quad image properties. The distance between two quad populations in the space of image properties is measured by a metric $\eta$, and the distance between their parent galaxy populations in the space of galaxy properties is measured by $\zeta$. We find a well-defined relation between $\eta$ and $\zeta$. The discovered relation between the space of image properties and the space of galaxy properties allows for the observed galaxy population properties to be estimated from the properties of their quads, which will be conducted in a future paper.

Radio continuum emission from a tidal dwarf galaxy

ABSTRACT Tidal dwarf galaxies (TDGs) form in the debris of galaxy mergers, making them ideal testbeds for investigating star formation in an extreme environment. We present radio continuum EVLA observations spanning 1–2 GHz of the interacting system Arp 94, which contains the TDG J1023+1952. We detect extended radio continuum emission from the disc of the TDG’s putative parent galaxy, the spiral NGC 3227. The TDG lies in front of the spiral disc, partially overlapping in projection. This challenging alignment complicates the separation of the respective contributions of radio emission from the TDG and disc. However, we show that the radio continuum appears more prominent around the TDG’s location, suggesting the detection of emission from the TDG. Quantifying this argument, we derive an upper limit of 2.2 mJy for the whole TDG’s emission. Our derived inband spectral index map of the system generally shows the expected behaviour of combined thermal and synchrotron radio emission in a galaxy disc, except for a region at the periphery of the disc and the TDG with a flat spectrum (spectral index $\sim$−0.4) unrelated to regions with high H $\alpha$ emission. We speculate that at this location – which coincides with the intersection of faint tidal tails – the collision of gas clouds produces shocks which re-accelerate cosmic ray electrons, and thereby enhance the radio emission. Overall, this study provides new insights about the Arp 94 system and expands the sample of TDGs studied at radio frequencies, with only two confirmed detections so far.

ЖИТТЯ ГАЛАКТИК У СПОСТЕРЕЖУВАНОМУ ВСЕСВІТІ. ЧАСТИНА 2

The exchange of hydrogen between galaxies and the galactic structures that ensure this process are considered. This exchange between the main objects of the Universe was given in the first part of the article, but it was not considered there as another and important process of the galactic cycle. However, the largest structures in the observable Universe are associated with the exchange of the lightest gas. This circumstance allows us to rightfully distinguish it as the next process of the galactic cycle. In the second process, determined by the phase of the quasar in the galactic core, stellar waste is disposed of. Weak quasar jets eject the results of recycling either into the halo of their own galaxy or into its immediate vicinity. From these emissions, stars are formed directly in the galaxy, or near it. As a rule, these are stars from the galaxy's own matter. High-speed jets contain particles at their bases that move at speeds faster than the speed of light. This allows jets to eject matter far beyond the boundaries of the parent galaxy. The matter of such a jet leaves the galaxy forever. Quasars turn on periodically and relatively rarely change the direction of their emissions. Therefore, they often send streams of matter in one direction. Observable intergalactic filaments are formed from energetic flows. Given that clusters contain many galaxies and each of them goes through quasar stages, several filaments may emerge from the cluster. Therefore, filaments begin and end on galaxies, or their clusters. Outgoing filaments, if they are located nearby and equally directed, can unite with each other, forming large filaments. The question of the forces contributing to the unification of almost parallel jets remains open. The filaments contain hot hydrogen, some dust, “metals,” stars and galaxies. Hydrogen in filaments is expected with a minimal percentage of “metals”. In the filaments, stars and galaxies can form from the available gas. This often happens where the threads intersect with each other. Filaments from other sources fall into the gravitational field of a galaxy, or cluster of galaxies. By delivering the necessary building material, filaments introduce new stellar life into the basic elements of the Universe. Therefore, filaments are channels that provide life to galaxies. This process of hydrogen exchange between galaxies is the fourth galactic process. He refines the model of galaxy life in the observable Universe, which is presented in the first part of the article

Horizontal branch structure, age, and chemical composition for very metal-poor extragalactic globular clusters

ABSTRACT This paper presents the results of analysing the integrated light (IL) low-resolution spectra of globular clusters (GCs) in the M31 and Centaurus A groups of galaxies. The sample consists of eight very metal-poor GCs ($\rm [Fe/H]\le -2$ dex) with high signal-to-noise ratio spectra acquired with the telescopes: the 6-m SAO RAS (BTA), the Southern African Large (SALT), and the 6.5-m Magellan (MMT). We study the influence of contribution of the horizontal branch stars on the hydrogen Balmer line profiles in the IL spectra. By modelling the Balmer lines, as well as the metal lines in the observed spectra, we determine the optimum parameters of stellar evolution isochrones and, consequently, the parameters of the atmospheres of the cluster stars. For all the studied GCs, the parameters of horizontal branch stars set by the selected isochrones, the corresponding ages, and carbon abundances are presented for the first time. The abundances of several other elements (Mg, Ca, Ti, Cr, and Mn) were determined for five GCs for the first time. All the studied GCs have blue horizontal branches and are older than 10 Gyr. Their chemical abundances, with the exception of Mg and Mn, are in good agreement with the abundances of stars in the Galactic field. The reasons of low [Mg/Fe] and of high [Mn/Fe] are discussed. Study of the fundamental properties of stellar populations in old GCs facilitates a better understanding of the formation processes of their parent galaxies and nucleosynthesis in the early Universe.

The role of environment on the formation of different FR type extragalactic radio sources

We study the environment of nearby extragalactic radio sources of different morphological type from our sample. We chose 30 3C radio galaxies of different FR class for which we have several observational dates on wavelength from radio to X ray. For the study we select the regions with radius of 500 pc around of the parent galaxy of radio sources. We bring the optical maps of these regions that are overlaid on the radio maps and maps in all available wavelength. The preliminary review show that there are some differences in the neighboring regions around radio galaxies of different FR classes.

Investigation of globular cluster of irregular galaxies

The objects of study are irregular galaxies and the corresponding systems of globular clusters (GCS). The purpose of this article is to compile a list of irregular galaxies containing GCS and find a statistical relationship between the physical parameters. Additionally, let’s aim to develop a method for constructing a non-stationary theory of their origin. It is noteworthy that only a limited number of results from observational data on the study of GCS in irregular galaxies have been published before. It has been identified 23 instances of GCS around irregular galaxies through observations. Based on observational data, lists of irregular galaxies containing the GCS were compiled. Im-type irregular galaxies are found to contain the largest number of GCS. Primarily, GCS are observed in Im-, Sm-, and dIr-type galaxies. The average number of clusters is dominated by Sm-type galaxies. In addition, dwarf irregular galaxies contain few clusters, and the absolute magnitude of their parent galaxies is smaller.
 Empirical relationships between the parameters of GCS and their parent galaxies are established. A linear dependence of the logarithm of the number of globular clusters in the system on the absolute magnitude of the host galaxy has been found. The study demonstrates that as the number of globular clusters increases, the mass of the host galaxy shows a linear growth. Additionally, a potential approach to the GCS origin theory has been explored in irregular galaxies by analyzing oscillation modes against the background of the collapse model

Pairing Optical and Atomic Hydrogen Detections to Assess Newly-Discovered Galaxy Candidates

As optical telescopes become more advanced, their detections begin to unveil very faint, previously unobserved extragalactic objects in the night sky – some of which could be among the smallest and most diffuse galaxies ever discovered. Many of the objects detected appear to be comprised of young, blue stars which seem to exist in isolation from any parent galaxies. In this research, we attempt to connect the very faint optical detections with atomic hydrogen, HI, detections from archival surveys, in order to assess the likelihood that they are newly-discovered galaxies and whether they are actively forming stars. Using the Systematically Measuring Ultra-diffuse Galaxies (SMUDGes) catalog to generate a list of potential candidates, the HI profile corresponding to each candidate’s coordinates was generated and smoothed, ensuring the detection of subtle emissions. Out of the 48 candidates analyzed, 2 very promising candidates emerged and properties like the object’s recessional velocity and HI mass were determined. While the lack of emissions detected may point to radio surveys not being deep enough to detect subtle HI emissions, observing these successful candidates may allow for the formation, origins and evolution of these objects to be studied, thus expanding our knowledge of the universe and galaxy formations.

Europium enrichment and hierarchical formation of the Galactic halo

Context.The origin of the large star-to-star variation of the [Eu/Fe] ratios observed in the extremely metal-poor (at [Fe/H] ≤ −3) stars of the Galactic halo is still a matter of debate.Aims.In this paper, we explore this problem by putting our stochastic chemical evolution model in the hierarchical clustering framework, with the aim of explaining the observed spread in the halo.Methods.We compute the chemical enrichment of Eu occurring in the building blocks that have possibly formed the Galactic halo. In this framework, the enrichment from neutron star mergers can be influenced by the dynamics of the binary systems in the gravitational potential of the original host galaxy. In the least massive systems, the neutron stars can merge outside the host galaxy and so only a small fraction of newly produced Eu can be retained by the parent galaxy itself.Results.In the framework of this new scenario, the accreted merging neutron stars are able to explain the presence of stars with sub-solar [Eu/Fe] ratios at [Fe/H] ≤ −3, but only if we assume a delay time distribution for merging of the neutron stars ∝t−1.5. We confirm the correlation between the dispersion of [Eu/Fe] at a given metallicity and the fraction of massive stars which give origin to neutron star mergers. The mixed scenario, where both neutron star mergers and magneto-rotational supernovae do produce Eu, can explain the observed spread in the Eu abundance also for a delay time distribution for mergers going either as ∝t−1or ∝t−1.5.

Intracluster light in the core of z ∼ 2 galaxy proto-clusters

ABSTRACT Intracluster light is thought to originate from stars that were ripped away from their parent galaxies by gravitational tides and galaxy interactions during the build up of the cluster. The stars from such interactions will accumulate over time, so semi-analytic models suggest that the abundance of intracluster stars is negligible in young proto-clusters at z∼ 2 and grows to around a quarter of the stellar mass in the oldest, most mature clusters. In contrast to these theoretical expectations, we report on the detection of intracluster light within two proto-clusters at z= 2 using deep HST images. We use the colour of the intracluster light to estimate its mass-to-light ratio in annuli around the brightest cluster galaxies (BCG), up to a radius of 100 kpc. We find that 54 ± 5 per cent and 71 ± 3 per cent of the stellar mass in these regions is located more than 10 kpc away from the BCGs in the two proto-clusters. This low concentration is similar to BCGs in lower redshift clusters, and distinct from other massive proto-cluster galaxies. This suggests that intracluster stars are already present within the core 100 kpc of proto-clusters. We compare these observations to the Hydrangea hydrodynamical galaxy cluster simulations and find that intracluster stars are predicted to be a generic feature of group-sized haloes at z= 2. These intracluster stars will gradually move further away from the BCG as the proto-cluster assembles into a cluster.

The chemical DNA of the Magellanic Clouds

We present the chemical composition of 206 red giant branch stars that are members of the Small Magellanic Cloud (SMC) using optical high-resolution spectra collected with the multi-object spectrograph FLAMES-GIRAFFE at the ESO Very Large Telescope. This sample includes stars in three fields that are located in different positions within the parent galaxy. We analysed the main groups of elements, namely light- (Na), α- (O, Mg, Si, Ca, and Ti), iron-peak (Sc, V, Fe, Ni, and Cu), and s-process elements (Zr, Ba, and La). The metallicity distribution of the sample displays a main peak around [Fe/H]∼–1 dex and a weak metal-poor tail. However, the three fields display different [Fe/H] distributions. In particular, a difference of 0.2 dex is found between the mean metallicities of the two innermost fields. The fraction of metal-poor stars increases significantly (from ∼1 to ∼20%) from the innermost fields to the outermost field, likely reflecting an age gradient in the SMC. We also found an indication of possible chemically and kinematic distinct substructures. The ratios of the SMC stars are clearly distinct from those of Milky Way stars, in particular, for the elements produced by massive stars (e.g. Na, α, and most iron-peak elements), whose abundance ratios are systematically lower than those measured in our Galaxy. This shows that massive stars contributed less to the chemical enrichment of the SMC than the Milky Way, according to the low star formation rate expected for this galaxy. Finally, we identified small systematic differences in the abundances of some elements (Na, Ti, V, and Zr) in the two innermost fields, suggesting that the chemical enrichment history in the SMC has not been uniform.

Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. II. A New Class of Stellar System

We discuss five blue stellar systems in the direction of the Virgo cluster, analogous to the enigmatic object SECCO 1 (AGC 226067). These objects were identified based on their optical and UV morphology and followed up with H i observations with the Very Large Array (and Green Bank Telescope), Multi Unit Spectroscopic Explorer (on the Very Large Telescope) optical spectroscopy, and Hubble Space Telescope imaging. These new data indicate that one system is a distant group of galaxies. The remaining four are extremely low mass (M * ∼ 105 M ⊙), are dominated by young blue stars, have highly irregular and clumpy morphologies, are only a few kiloparsecs across, yet host an abundance of metal-rich, , H ii regions. These high metallicities indicate that these stellar systems formed from gas stripped from much more massive galaxies. Despite the young age of their stellar populations, only one system is detected in H i, while the remaining three have minimal (if any) gas reservoirs. Furthermore, two systems are surprisingly isolated and have no plausible parent galaxy within ∼30′ (∼140 kpc). Although tidal stripping cannot be conclusively excluded as the formation mechanism of these objects, ram pressure stripping more naturally explains their properties, in particular their isolation, owing to the higher velocities, relative to the parent system, that can be achieved. Therefore, we posit that most of these systems formed from ram-pressure-stripped gas removed from new infalling cluster members and survived in the intracluster medium long enough to become separated from their parent galaxies by hundreds of kiloparsecs and that they thus represent a new type of stellar system.

Why most molecular clouds are gravitationally dominated

ABSTRACT Observational and theoretical evidence suggests that a substantial population of molecular clouds (MCs) appear to be unbound, dominated by turbulent motions. However, these estimations are made typically via the classical virial parameter $\alpha _{\rm vir}^{\rm class}$, which is an observational proxy to the virial ratio between the kinetic and the gravitational energy. This parameter intrinsically assumes that MCs are isolated, spherical, and with constant density. However, MCs are embedded in their parent galaxy and thus are subject to compressive and disruptive tidal forces from their galaxy, exhibit irregular shapes, and show substantial substructure. We, therefore, compare the typical estimations of $\alpha _{\rm vir}^{\rm class}$ to a more precise definition of the virial parameter, $\alpha _{\rm vir}^{\rm full}$, which accounts not only for the self-gravity (as $\alpha _{\rm vir}^{\rm class}$), but also for the tidal stresses, and thus, it can take negative (self-gravity) and positive (tides) values. While we recover the classical result that most of the clouds appear to be unbound, having $\alpha _{\rm vir}^{\rm class}\gt 2$, we show that, with the more detailed definition considering the full gravitational energy, (i) 50 per cent of the total population is gravitationally bound, however, (ii) another 20 per cent is gravitationally dominated, but with tides tearing them apart; (iii) the source of those tides does not come from the galactic structure (bulge, halo, spiral arms), but from the molecular cloud complexes in which clouds reside, and probably (iv) from massive young stellar complexes, if they were present. (v) Finally, our results also suggest that, interstellar turbulence can have, at least partially, a gravitational origin.

Comparing NED and SIMBAD classifications across the contents of nearby galaxies

ABSTRACT Cataloguing and classifying celestial objects is one of the fundamental activities of observational astrophysics. In this work, we compare the contents of two comprehensive data bases, the NASA Extragalactic Database (NED) and Set of Identifications, Measurements and Bibliography for Astronomical Data (SIMBAD) in the vicinity of nearby galaxies. These two data bases employ different classification schemes – one flat and one hierarchical – and our goal was to determine the compatibility of classifications for objects in common. Searching both data bases for objects within the respective isophotal radius of each of the ∼1300 individual galaxies in the Local Volume Galaxy sample, we found that, on average, NED contains about 10 times as many entries as SIMBAD and about two-thirds of SIMBAD objects are matched by position to a NED object, at 5 arcsec tolerance. These quantities do not depend strongly on the properties of the parent galaxies. We developed an algorithm to compare individual object classifications between the two data bases and found that 88 per cent of the classifications agree; we conclude that NED and SIMBAD contain consistent information for sources in common in the vicinity of nearby galaxies. Because many galaxies have numerous sources contained only in one of NED or SIMBAD, researchers seeking the most complete picture of an individual galaxy’s contents are best served by using both data bases.

SDSS-IV MaNGA: spatial resolved properties of kinematically misaligned galaxies

ABSTRACT We select 456 galaxies with kinematically misaligned gas and stellar components from 9456 parent galaxies in MaNGA, and classify them into 72 star-forming galaxies, 142 green-valley galaxies, and 242 quiescent galaxies. Comparing the spatial resolved properties of the misaligned galaxies with control samples closely match in the Dn4000 and stellar velocity dispersion, we find that: (1) the misaligned galaxies have lower values in Vgas/σgas and Vstar/σstar (the ratio between ordered to random motion of gas and stellar components) across the entire galaxies than their control samples; (2) the star-forming and green-valley misaligned galaxies have enhanced central concentrated star formation than their control galaxies. The difference in stellar population between quiescent misaligned galaxies and control samples is small; (3) gas-phase metallicity of the green valley and quiescent misaligned galaxies are lower than the control samples. For the star-forming misaligned galaxies, the difference in metallicity between the misaligned galaxies and their control samples strongly depends on how we select the control samples. All these observational results suggest that external gas accretion influences the evolution of star forming and green-valley galaxies, not only in kinematics/morphologies, but also in stellar populations. However, the quiescent misaligned galaxies have survived from different formation mechanisms.

Is FRB 191001 embedded in a supernova remnant?

ABSTRACT Fast radio burst (FRB) 191001 is localized at the spiral arm of a highly star-forming galaxy with an observed dispersion measure (DM) of 507 $\mbox{pc cm$^{-3}$}$. Subtracting the contributions of the intergalactic medium and our Milky Way Galaxy from the total DM, one gets an excess of around 200 $\mbox{pc cm$^{-3}$}$, which may have been contributed by the host galaxy of the FRB. It is found in this work that the position of FRB 191001 is consistent with the distribution of supernovae (SNe) in the spiral arm of their parent galaxies. If this event is indeed due to an SN explosion, then, from the analysis of the SN contributions to the excess DM, a core-collapse (CC) channel is preferred over a thermonuclear runaway. For the CC explosion, depending on the density of the surrounding medium, the age of the central engine that powers the radio burst is within a couple of years to a few decades. However, the observed rotation measure of FRB 191001 does not confirm the fact that the radio burst has passed through the remnant of a young SN.

Supernova siblings and their parent galaxies in the Zwicky Transient Facility Bright Transient Survey

ABSTRACT Supernova (SN) siblings – two or more SNe in the same parent galaxy – are useful tools for exploring progenitor stellar populations as well as properties of the host galaxies such as distance, star-formation rate, dust extinction, and metallicity. Since the average SN rate for a Milky Way-type galaxy is just one per century, a large imaging survey is required to discover an appreciable sample of SN siblings. From the wide-field Zwicky Transient Facility (ZTF) Bright Transient Survey (which aims for spectroscopic completeness for all transients which peak brighter than r < 18.5 mag) we present 10 SN siblings in five parent galaxies. For each of these families, we analyse the SN’s location within the host and its underlying stellar population, finding agreement with expectations that SNe from more massive progenitors are found nearer to their host core and in regions of more active star formation. We also present an analysis of the relative rates of core collapse and thermonuclear SN siblings, finding a significantly lower ratio than past SN sibling samples due to the unbiased nature of the ZTF.