29 research outputs found
How limiting is optical follow-up for fast radio burst applications? Forecasts for radio and optical surveys
Fast radio bursts (FRBs) are the first cosmological radio sources that vary
on millisecond timescales, which makes them a unique probe of the Universe.
Many proposed applications of FRBs require associated redshifts. These can only
be obtained by localizing FRBs to their host galaxies and subsequently
measuring their redshifts. Upcoming FRB surveys will provide arcsecond
localization for many FRBs, not all of which can be followed up with dedicated
optical observations. We aim to estimate the fraction of FRB hosts that will be
catalogued with redshifts by existing and future optical surveys. We use the
population synthesis code frbpoppy to simulate several FRB surveys, and the
semi-analytical galaxy formation code GALFORM to simulate their host galaxies.
We obtain redshift distributions for the simulated FRBs and the fraction with
host galaxies in a survey. Depending on whether FRBs follow the cosmic star
formation rate or stellar mass, 20 to 40 per cent of CHIME FRB hosts will be
observed in an SDSS-like survey, all at . The deeper DELVE survey will
detect 63 to 85 per cent of ASKAP FRBs found in its coherent search mode. CHIME
FRBs will reach , SKA1-Mid FRBs , but ground based follow-up
is limited to . We discuss consequences for several FRB
applications. If of ASKAP FRBs have measured redshifts, 1000 detected
FRBs can be used to constrain to within per
cent at 95 per cent credibility. We provide strategies for optimized follow-up,
when building on data from existing surveys. Data and codes are made available.Comment: 18 pages, 16 figures, 4 tables, accepted for publication in MNRAS.
Code available at https://github.com/JoschaJ/mockFRBhost
Current and Nascent SETI Instruments
Here we describe our ongoing efforts to develop high-performance and
sensitive instrumentation for use in the search for extra-terrestrial
intelligence (SETI). These efforts include our recently deployed Search for
Extraterrestrial Emissions from Nearby Developed Intelligent Populations
Spectrometer (SERENDIP V.v) and two instruments currently under development;
the Heterogeneous Radio SETI Spectrometer (HRSS) for SETI observations in the
radio spectrum and the Optical SETI Fast Photometer (OSFP) for SETI
observations in the optical band. We will discuss the basic SERENDIP V.v
instrument design and initial analysis methodology, along with instrument
architectures and observation strategies for OSFP and HRSS. In addition, we
will demonstrate how these instruments may be built using low-cost, modular
components and programmed and operated by students using common languages, e.g.
ANSI C.Comment: 12 pages, 5 figures, Original version appears as Chapter 2 in "The
Proceedings of SETI Sessions at the 2010 Astrobiology Science Conference:
Communication with Extraterrestrial Intelligence (CETI)," Douglas A. Vakoch,
Edito
VOEvent Standard for Fast Radio Bursts
Fast radio bursts are a new class of transient radio phenomena currently
detected as millisecond radio pulses with very high dispersion measures. As new
radio surveys begin searching for FRBs a large population is expected to be
detected in real-time, triggering a range of multi-wavelength and
multi-messenger telescopes to search for repeating bursts and/or associated
emission. Here we propose a method for disseminating FRB triggers using Virtual
Observatory Events (VOEvents). This format was developed and is used
successfully for transient alerts across the electromagnetic spectrum and for
multi-messenger signals such as gravitational waves. In this paper we outline a
proposed VOEvent standard for FRBs that includes the essential parameters of
the event and where these parameters should be specified within the structure
of the event. An additional advantage to the use of VOEvents for FRBs is that
the events can automatically be ingested into the FRB Catalogue (FRBCAT)
enabling real-time updates for public use. We welcome feedback from the
community on the proposed standard outlined below and encourage those
interested to join the nascent working group forming around this topic.Comment: 11 pages, 2 figures, parameter definition table in appendi
No Radio Bursts Detected from FIRST J141918.9+394036 in Green Bank Telescope Observations
Precise localization of the first-known repeating fast radio burst source, FRB 121102 (Spitler et al. 2016; Chatterjee et al. 2017), led to its association with a star-forming region inside a low-metallicity dwarf host galaxy (Tendulkar et al. 2017). This host environment is similar to that typically associated with long gamma-ray bursts (GRB) and superluminous supernovae, potentially linking these astrophysical phenomena (Metzger et al. 2017). In addition, the bursting source is found to be spatially coincident with a compact (< 0.7 pc; Marcote et al. 2017), persistent radio source (Chatterjee et al. 2017). Ofek (2017) identified similar radio sources in the Very Large Array FIRST survey (Becker et al. 1995). One of these sources, FIRST J141918.9+394036 (hereafter FIRST J1419+3940), was identified as a radio transient decaying in brightness by a factor of ~50 over several decades (Law et al. 2018). Very-long-baseline radio interferometric observations support the theory that FIRST J1419+3940 is the afterglow of a long GRB, based on the inferred physical size of the emission region (1.6 ± 0.3 pc; Marcote et al. 2019)
No Radio Bursts Detected from FIRST J141918.9+394036 in Green Bank Telescope Observations
Precise localization of the first-known repeating fast radio burst source, FRB 121102 (Spitler et al. 2016; Chatterjee et al. 2017), led to its association with a star-forming region inside a low-metallicity dwarf host galaxy (Tendulkar et al. 2017). This host environment is similar to that typically associated with long gamma-ray bursts (GRB) and superluminous supernovae, potentially linking these astrophysical phenomena (Metzger et al. 2017). In addition, the bursting source is found to be spatially coincident with a compact (< 0.7 pc; Marcote et al. 2017), persistent radio source (Chatterjee et al. 2017). Ofek (2017) identified similar radio sources in the Very Large Array FIRST survey (Becker et al. 1995). One of these sources, FIRST J141918.9+394036 (hereafter FIRST J1419+3940), was identified as a radio transient decaying in brightness by a factor of ~50 over several decades (Law et al. 2018). Very-long-baseline radio interferometric observations support the theory that FIRST J1419+3940 is the afterglow of a long GRB, based on the inferred physical size of the emission region (1.6 ± 0.3 pc; Marcote et al. 2019)
The ACS Fornax Cluster Survey VII. Half-Light Radii of Globular Clusters in Early-Type Galaxies
We measure the half-light radii of globular clusters (GCs) in 43 galaxies
from the ACS Fornax Cluster Survey (ACSFCS). We use these data to extend
previous work in which the environmental dependencies of the half-light radii
of GCs in early type galaxies in the ACS Virgo Cluster Survey (ACSVCS) were
studied, and a corrected mean half-light radius (corrected for the observed
environmental trends) was suggested as a reliable distance indicator. This work
both increases the sample size for the study of the environmental dependencies,
and adds leverage to the study of the corrected half-light radius as a possible
distance indicator (since Fornax lies at a larger distance than the Virgo
cluster). We study the environmental dependencies of the size of GCs using both
a Principal Component Analysis as well as 2D scaling relations. We largely
confirm the environmental dependencies shown in Jordan et al. (2005), but find
evidence that there is a residual correlation in the mean half-light radius of
GC systems with galaxy magnitude, and subtle differences in the other
correlations - so there may not be a universal correction for the half-light
radii of lower luminosity galaxy GC systems. The main factor determining the
size of a GC in an early type galaxy is the GC color. Red GCs have =
2.8+/-0.3 pc, while blue GCs have = 3.4+/-0.3 pc. We show that for bright
early-type galaxies (M_B < -19 mag), the uncorrected mean half-light radius of
the GC system is by itself an excellent distance indicator (with error ~11%),
having the potential to reach cosmologically interesting distances in the era
of high angular resolution adaptive optics on large optical telescopes.Comment: ApJ in press, 19 pages, 16 figures
Limits on Enhanced Radio Wave Scattering by Supernova Remnants
We report multifrequency observations with the NRAO Very Long Baseline Array
(VLBA) of the compact radio sources J0128+6306 and J0547+2721, which are viewed
through the supernova remnants G127.1+0.5 and S147, respectively. Observations
were made at frequencies of 1.427, 1.667, 2.271, and 4.987 GHz. The lines of
sight to these sources pass through the shock wave and upstream and downstream
turbulent layers of their respective supernova remnants, and thus might detect
cosmic-ray generated turbulence produced during the Fermi acceleration process.
For both sources, we detect interstellar scattering, characterized by a
component of the angular size which scales as the square of the observing
wavelength. The magnitude of the scattering is characterized by an effective
scattering angular size theta_S0 at a frequency of 1 GHz of 13.2 +/- 2.6
milliarcseconds (mas) for J0128+6306 and 6.7 +/- 2.2 mas for J0547+2721. These
angular sizes are consistent with the ``incidental'' scattering for any line of
sight out of the galaxy at similar galactic latitudes and longitudes. There is
therefore no evidence for enhanced turbulence at these supernova remnants. We
establish upper limits to the supernova remnant-associated scattering measures
of 8.1-14.8 m^-20/3-pc for J0128+6306 and 3.0 m^-20/3-pc for J0547+2721.Comment: To be published in ApJ, 25 pages, 4 figures, 2 table
The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102
The precise localization of the repeating fast radio burst (FRB 121102) has
provided the first unambiguous association (chance coincidence probability
) of an FRB with an optical and persistent radio
counterpart. We report on optical imaging and spectroscopy of the counterpart
and find that it is an extended ()
object displaying prominent Balmer and [OIII] emission lines. Based on the
spectrum and emission line ratios, we classify the counterpart as a
low-metallicity, star-forming, AB mag dwarf galaxy at a
redshift of , corresponding to a luminosity distance of 972 Mpc.
From the angular size, the redshift, and luminosity, we estimate the host
galaxy to have a diameter kpc and a stellar mass of
, assuming a mass-to-light ratio between 2 to
3. Based on the H flux, we estimate the star
formation rate of the host to be and a
substantial host dispersion measure depth .
The net dispersion measure contribution of the host galaxy to FRB 121102 is
likely to be lower than this value depending on geometrical factors. We show
that the persistent radio source at FRB 121102's location reported by Marcote
et al (2017) is offset from the galaxy's center of light by 200 mas and
the host galaxy does not show optical signatures for AGN activity. If FRB
121102 is typical of the wider FRB population and if future interferometric
localizations preferentially find them in dwarf galaxies with low metallicities
and prominent emission lines, they would share such a preference with long
gamma ray bursts and superluminous supernovae.Comment: 12 pages, 3 figures, Published in ApJ Letters. V2: Corrected mistake
in author lis
The ACS Fornax Cluster Survey. IX. The Color-Magnitude Relation of Globular Cluster Systems
We investigate the color-magnitude relation for globular clusters (GCs) --
the so-called "blue tilt" -- detected in the ACS Fornax Cluster Survey and
using the combined sample of GCs from the ACS Fornax and Virgo Cluster Surveys.
We find a tilt of gamma_z=d(g-z)/dz=-0.0257 +- 0.0050 for the full GC sample of
the Fornax Cluster Survey (~5800 GCs). This is slightly shallower than the
value gamma_z=-0.0459 +- 0.0048 found for the Virgo Cluster Survey GC sample
(~11100 GCs). The slope for the merged Fornax and Virgo datasets (~16900 GCs)
is gamma_z=-0.0293 +- 0.0085, corresponding to a mass-metallicity relation of Z
~ M^0.43. We find that the blue tilt sets in at GC masses in excess of M ~
2*10^5 M_sun. The tilt is stronger for GCs belonging to high-mass galaxies (M_*
> 5 * 10^10 M_sun) than for those in low-mass galaxies (M_* < 5 * 10^10 M_sun).
It is also more pronounced for GCs with smaller galactocentric distances. Our
findings suggest a range of mass-metallicity relations Z_GC ~ M_GC^(0.3-0.7)
which vary as a function of host galaxy mass/luminosity. We compare our
observations to a recent model of star cluster self-enrichment with generally
favorable results. We suggest that, within the context of this model, the
proto-cluster clouds out of which the GCs formed may have had density profiles
slightly steeper than isothermal and/or star formation efficiencies somewhat
below 0.3. We caution, however, that the significantly different appearance of
the CMDs defined by the GC systems associated with galaxies of similar mass and
morphological type pose a challenge to any single mechanism that seeks to
explain the blue tilt. We therefore suggest that the merger/accretion histories
of individual galaxies have played a non-negligible role determining the
distribution of GCs in the CMDs of individual GC systems