24 research outputs found
The Host Galaxies of Sub-Chandrasekhar Mass Type Ia Supernovae
In recent years, there has been ample evidence for the existence of multiple
progenitor pathways that can result in Type Ia supernova (SNe Ia), including
SNe Ia of sub-Chandrasekhar mass origin best distinguished by their redder
colors and higher Si II velocities near peak brightness. These SNe can
contaminate the population of normal events used for cosmological analyses,
creating unwanted biases in the final analyses. Given that many current and
future surveys using SNe Ia as cosmological probes will not have the resources
to take a spectrum of all the events, likely only getting host redshifts long
after the SNe Ia have faded, we need to turn to methods that could separate
these populations based purely on photometry or host properties. Here, we
present a study of a sample of well observed, nearby SNe Ia and their hosts to
determine if there are significant enough difference between these populations
that can be discerned only from the stellar population properties of their
hosts. Our results indicate that the global host properties, including star
formation, stellar mass, stellar population age, and dust attenuation, of
sub-Chandrasekhar mass explosions do not differ significantly from those of
normal mass origin. However, we do find evidence using Na I D equivalent widths
that the local environments of sub-Chandrasekhar mass explosions are more
dust-affected than normal SNe Ia. Future work requires strengthening
photometric probes of sub-Chandrasekhar SNe and their local environments to
distinguish these events.Comment: 16 pages, 10 figures, 2 tables, submitte
A Population of Short-duration Gamma-ray Bursts with Dwarf Host Galaxies
We present a population of 11 of the faintest ( AB mag) short
gamma-ray burst (GRB) host galaxies. We model their sparse available
observations using the stellar population inference code Prospector- and
develop a novel implementation to incorporate the galaxy mass-radius relation.
Assuming these hosts are randomly drawn from the galaxy population and
conditioning this draw on their observed flux and size in few photometric
bands, we determine that these hosts have dwarf galaxy stellar masses of
. This is striking as only of
short GRB hosts with previous inferred stellar masses had . We further show these short GRBs have smaller physical and
host-normalized offsets than the rest of the population, suggesting that the
majority of their neutron star (NS) merger progenitors were retained within
their hosts. The presumably shallow potentials of these hosts translate to
small escape velocities of km/s, indicative of either low
post-supernova systemic velocities or short inspiral times. While short GRBs
with identified dwarf host galaxies now comprise of the total
Swift-detected population, a number are likely missing in the current
population, as larger systemic velocities (observed from Galactic NS
population) would result in highly offset short GRBs and less secure host
associations. However, the revelation of a population of short GRBs retained in
low-mass host galaxies offers a natural explanation for observed -process
enrichment via NS mergers in Local Group dwarf galaxies, and has implications
for gravitational wave follow-up strategies.Comment: 22 pages, 9 figures, 2 tables, submitte
The distant, galaxy cluster environment of the short GRB 161104A at and a comparison to the short GRB host population
We present optical observations of the Swift short-duration gamma-ray burst
(GRB) GRB 161104A and its host galaxy at . We model the
multiband photometry and spectroscopy with the stellar population inference
code Prospector, and explore the posterior using nested sampling. We find that
the mass-weighted age ~Gyr, stellar mass
, metallicity , dust extinction mag, and
the star formation rate ~yr.
These properties, along with a prominent 4000 Angstrom break and optical
absorption lines classify this host as an early-type, quiescent galaxy. Using
Dark Energy Survey galaxy catalogues, we demonstrate that the host of GRB
161104A resides on the outskirts of a galaxy cluster at ,
situated Mpc from the likely brightest cluster galaxy. We also
present new modeling for 20 additional short GRB hosts ( of which
are early-type galaxies), finding population medians of and ~Gyr ( confidence).
We further find that the host of GRB 161104A is more distant, less massive, and
younger than the four other short GRB hosts known to be associated with galaxy
clusters. Cluster short GRBs have faint afterglows, in the lower
() of observed X-ray (optical) luminosities. We place a lower
limit on the fraction of short GRBs in galaxy clusters versus those in the
field of , consistent with the fraction of stellar mass
in galaxy clusters at redshifts .Comment: 20 pages, 9 figures, ApJ: Vol. 904, No.
Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
We present the stellar population properties of 69 short gamma-ray burst
(GRB) host galaxies, representing the largest uniformly-modeled sample to-date.
Using the Prospector stellar population inference code, we jointly fit
photometry and/or spectroscopy of each host galaxy. We find a population median
redshift of ( confidence), including 10 new or
revised photometric redshifts at . We further find a median
mass-weighted age of Gyr, stellar mass of
, star formation rate of
SFR=yr, stellar metallicity of
, and dust attenuation of
~mag (68\% confidence). Overall, the majority of
short GRB hosts are star-forming (), with small fractions that are
either transitioning () or quiescent (); however, we
observe a much larger fraction () of quiescent and transitioning
hosts at , commensurate with galaxy evolution. We find that
short GRB hosts populate the star-forming main sequence of normal field
galaxies, but do not include as many high-mass galaxies, implying that their
binary neutron star (BNS) merger progenitors are dependent on a combination of
host star formation and stellar mass. The distribution of ages and redshifts
implies a broad delay-time distribution, with a fast-merging channel at
and a decreased BNS formation efficiency at lower redshifts. If short GRB hosts
are representative of BNS merger hosts within the horizon of current
gravitational wave detectors, these results can inform future searches for
electromagnetic counterparts. All of the data and modeling products are
available on the BRIGHT website.Comment: 32 pages, 15 figures, 3 tables, accepted to Ap
SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Massive Helium-Shell Detonation in a Star-Forming Galaxy
The detonation of a thin () helium shell
(He-shell) atop a white dwarf (WD) is a promising
mechanism to explain normal Type Ia supernovae (SNe Ia), while thicker
He-shells and less massive WDs may explain some recently observed peculiar SNe
Ia. We present observations of SN 2020jgb, a peculiar SN Ia discovered by the
Zwicky Transient Facility (ZTF). Near maximum light, SN 2020jgb is slightly
subluminous (ZTF -band absolute magnitude between and
mag depending on the amount of host galaxy extinction) and shows an unusually
red color ( between 0.4 and 0.2 mag) due to
strong line-blanketing blueward of 5000 . These properties
resemble those of SN 2018byg, a peculiar SN Ia consistent with a thick He-shell
double detonation (DDet) SN. Using detailed radiative transfer models, we show
that the optical spectroscopic and photometric evolution of SN 2020jgb are
broadly consistent with a (C/O core + He-shell;
up to depending on the total host extinction)
progenitor ignited by a thick () He-shell. We
detect a prominent absorption feature at 1 in the
near-infrared (NIR) spectrum of SN 2020jgb, which could originate from unburnt
helium in the outermost ejecta. While the sample size is limited, similar 1
features have been detected in all the thick He-shell DDet
candidates with NIR spectra obtained to date. SN 2020jgb is also the first
subluminous, thick He-shell DDet SN discovered in a star-forming galaxy,
indisputably showing that He-shell DDet objects occur in both star-forming and
passive galaxies, consistent with the normal SN Ia population.Comment: 23 pages, 10 figures. Updated to accepted version (ApJ
A Fast Radio Burst in a Compact Galaxy Group at ~1
FRB 20220610A is a high-redshift Fast Radio Burst (FRB) that has not been
observed to repeat. Here, we present rest-frame UV and optical observations of the field of FRB 20220610A. The imaging
reveals seven extended sources, one of which we identify as the most likely
host galaxy with a spectroscopic redshift of =1.017. We spectroscopically
confirm at least three additional sources to be at the same redshift, and
identify the system as a compact galaxy group with possible signs of
interaction among group members. We determine the host of FRB 20220610A to be a
star-forming galaxy with stellar mass of ,
mass-weighted age of ~Gyr, and star formation rate (integrated over
the last 100 Myr) of ~M~yr. These host properties
are commensurate with the star-forming field galaxy population at z~1 and trace
their properties analogously to the population of low- FRB hosts. Based on
estimates of the total stellar mass of the galaxy group, we calculate a
fiducial contribution to the observed Dispersion Measure (DM) from the
intragroup medium of (rest-frame). This
leaves a significant excess of (in the
observer frame), with additional sources of DM possibly originating from the
circumburst environment, host galaxy interstellar medium, and/or foreground
structures along the line of sight. Given the low occurrence rates of galaxies
in compact groups, the discovery of an FRB in such a group demonstrates a rare
and novel environment in which FRBs can occur.Comment: 24 pages, 8 figures, 2 tables, submitte
Short GRB Host Galaxies I: Photometric and Spectroscopic Catalogs, Host Associations, and Galactocentric Offsets
We present a comprehensive optical and near-infrared census of the fields of
90 short gamma-ray bursts (GRBs) discovered in 2005-2021, constituting all
short GRBs for which host galaxy associations are feasible ( 60% of
the total Swift short GRB population). We contribute 245 new multi-band imaging
observations across 49 distinct GRBs and 25 spectra of their host galaxies.
Supplemented by literature and archival survey data, the catalog contains 335
photometric and 40 spectroscopic data sets. The photometric catalog reaches
depths of mag and mag for the optical
and near-infrared bands, respectively. We identify host galaxies for 84 bursts,
in which the most robust associations make up 54% (49/90) of events, while only
a small fraction, 6.7%, have inconclusive host associations. Based on new
spectroscopy, we determine 17 host spectroscopic redshifts with a range of
and find that 25-44% of Swift short GRBs
originate from . We also present the galactocentric offset catalog for 83
short GRBs. Taking into account the large range of individual measurement
uncertainties, we find a median of projected offset of kpc, for
which the bursts with the most robust associations have a smaller median of
kpc. Our catalog captures more high-redshift and low-luminosity
hosts, and more highly-offset bursts than previously found, thereby
diversifying the population of known short GRB hosts and properties. In terms
of locations and host luminosities, the populations of short GRBs with and
without detectable extended emission are statistically indistinguishable. This
suggests that they arise from the same progenitors, or from multiple
progenitors which form and evolve in similar environments. All of the data
products are available on the BRIGHT website.Comment: 53 pages, 9 figures, 6 tables, submitte
The Demographics, Stellar Populations, and Star Formation Histories of Fast Radio Burst Host Galaxies: Implications for the Progenitors
We present a comprehensive catalog of observations and stellar population
properties for 23 highly secure host galaxies of fast radio bursts (FRBs). Our
sample comprises six repeating FRBs and 17 apparent non-repeaters. We present
82 new photometric and eight new spectroscopic observations of these hosts.
Using stellar population synthesis modeling and employing non-parametric star
formation histories (SFHs), we find that FRB hosts have a median stellar mass
of , mass-weighted age Gyr, and
ongoing star formation rate yr but span wide
ranges in all properties. Classifying the hosts by degree of star formation, we
find that 87% (20/23 hosts) are star-forming, two are transitioning, and one is
quiescent. The majority trace the star-forming main sequence of galaxies, but
at least three FRBs in our sample originate in less active environments (two
non-repeaters and one repeater). Across all modeled properties, we find no
statistically significant distinction between the hosts of repeaters and
non-repeaters. However, the hosts of repeating FRBs generally extend to lower
stellar masses, and the hosts of non-repeaters arise in more optically luminous
galaxies. While four of the galaxies with the most clear and prolonged rises in
their SFHs all host repeating FRBs, demonstrating heightened star formation
activity in the last Myr, one non-repeating host shows this SFH
as well. Our results support progenitor models with short delay channels (i.e.,
magnetars formed via core-collapse supernova) for most FRBs, but the presence
of some FRBs in less active environments suggests a fraction form through more
delayed channels.Comment: 52 pages, 32 figures, 6 tables, submitte
Heavy element production in a compact object merger observed by JWST
The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs) 1, sources of high-frequency gravitational waves (GWs) 2 and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process) 3. Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers 4–6 and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. 7–12). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe
Observational Inference on the Delay Time Distribution of Short Gamma-ray Bursts
The delay time distribution of neutron star mergers provides critical
insights into binary evolution processes and the merger rate evolution of
compact object binaries. However, current observational constraints on this
delay time distribution rely on the small sample of Galactic double neutron
stars (with uncertain selection effects), a single multimessenger
gravitational-wave event, and indirect evidence of neutron star mergers based
on -process enrichment. We use a sample of 67 host galaxies of short
gamma-ray bursts to place novel constraints on the delay time distribution, and
leverage this result to infer the merger rate evolution of compact object
binaries containing neutron stars. We recover a power-law slope of and a minimum delay time of (median and 90% credible interval), with the
maximum delay time constrained to at 99%
credibility. We find these constraints to be broadly consistent with
theoretical expectations, although our recovered power-law slope is
substantially steeper than the conventional value of , and
our minimum delay time is larger than the typically assumed value of
. Pairing this cosmological probe of the fate of compact
object binary systems with the Galactic population of double neutron stars will
be crucial for understanding the unique selection effects governing both of
these populations. In addition to probing a significantly larger redshift
regime of neutron star mergers than possible with current gravitational-wave
detectors, complementing our results with future multimessenger
gravitational-wave events will also help determine if short gamma-ray bursts
ubiquitously result from compact object binary mergers.Comment: 13 pages, 3 figures, submitted to AAS Journal