21 research outputs found
Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers
The galaxy catalogs generated from low-resolution emission line surveys often
contain both foreground and background interlopers due to line
misidentification, which can bias the cosmological parameter estimation. In
this paper, we present a method for correcting the interloper bias by using the
joint-analysis of auto- and cross-power spectra of the main and the interloper
samples. In particular, we can measure the interloper fractions from the
cross-correlation between the interlopers and survey galaxies, because the true
cross-correlation must be negligibly small. The estimated interloper fractions,
in turn, remove the interloper bias in the cosmological parameter estimation.
For example, in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
low-redshift () [O II] {\AA} emitters contaminate
high-redshift () Lyman- line emitters. We demonstrate that
the joint-analysis method yields a high signal-to-noise ratio measurement of
the interloper fractions while only marginally increasing the uncertainties in
the cosmological parameters relative to the case without interlopers. We also
show the same is true for the high-latitude spectroscopic survey of Wide-Field
Infrared Survey Telescope (WFIRST) mission where contamination occurs between
the Balmer- line emitters at lower redshifts () and Oxygen
([O III] {\AA}) line emitters at higher redshifts ().Comment: 36 pages, 26 figure
Physical and Morphological Properties of [O II] Emitting Galaxies in the HETDEX Pilot Survey
The Hobby-Eberly Dark Energy Experiment pilot survey identified 284 [O II]
3727 emitting galaxies in a 169 square-arcminute field of sky in the redshift
range 0 < z < 0.57. This line flux limited sample provides a bridge between
studies in the local universe and higher-redshift [O II] surveys. We present an
analysis of the star formation rates (SFRs) of these galaxies as a function of
stellar mass as determined via spectral energy distribution fitting. The [O II]
emitters fall on the "main sequence" of star-forming galaxies with SFR
decreasing at lower masses and redshifts. However, the slope of our relation is
flatter than that found for most other samples, a result of the metallicity
dependence of the [O II] star formation rate indicator. The mass specific SFR
is higher for lower mass objects, supporting the idea that massive galaxies
formed more quickly and efficiently than their lower mass counterparts. This is
confirmed by the fact that the equivalent widths of the [O II] emission lines
trend smaller with larger stellar mass. Examination of the morphologies of the
[O II] emitters reveals that their star formation is not a result of mergers,
and the galaxies' half-light radii do not indicate evolution of physical sizes.Comment: 36 pages, 16 figures, 4 tables, accepted to Ap
IDCS J1426.5+3508: Cosmological implications of a massive, strong lensing cluster at Z = 1.75
The galaxy cluster IDCS J1426.5+3508 at z = 1.75 is the most massive galaxy
cluster yet discovered at z > 1.4 and the first cluster at this epoch for which
the Sunyaev-Zel'Dovich effect has been observed. In this paper we report on the
discovery with HST imaging of a giant arc associated with this cluster. The
curvature of the arc suggests that the lensing mass is nearly coincident with
the brightest cluster galaxy, and the color is consistent with the arc being a
star-forming galaxy. We compare the constraint on M200 based upon strong
lensing with Sunyaev-Zel'Dovich results, finding that the two are consistent if
the redshift of the arc is z > 3. Finally, we explore the cosmological
implications of this system, considering the likelihood of the existence of a
strongly lensing galaxy cluster at this epoch in an LCDM universe. While the
existence of the cluster itself can potentially be accomodated if one considers
the entire volume covered at this redshift by all current high-redshift cluster
surveys, the existence of this strongly lensed galaxy greatly exacerbates the
long-standing giant arc problem. For standard LCDM structure formation and
observed background field galaxy counts this lens system should not exist.
Specifically, there should be no giant arcs in the entire sky as bright in
F814W as the observed arc for clusters at z \geq 1.75, and only \sim 0.3 as
bright in F160W as the observed arc. If we relax the redshift constraint to
consider all clusters at z \geq 1.5, the expected number of giant arcs rises to
\sim15 in F160W, but the number of giant arcs of this brightness in F814W
remains zero. These arc statistic results are independent of the mass of IDCS
J1426.5+3508. We consider possible explanations for this discrepancy.Comment: 7 pages, 4 figures, Accepted to The Astrophysical Journa
The Stars of the HETDEX Survey. I. Radial Velocities and Metal-Poor Stars from Low-Resolution Stellar Spectra
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an unbiased, massively multiplexed spectroscopic survey, designed to measure the expansion history of the universe through low-resolution (R∼750) spectra of Lyman-Alpha Emitters. In its search for these galaxies, HETDEX will also observe a few 105 stars. In this paper, we present the first stellar value-added catalog within the internal second data release of the HETDEX Survey (HDR2). The new catalog contains 120,571 low-resolution spectra for 98,736 unique stars between 10∘) Galactic latitudes. With these spectra, we measure radial velocities (RVs) for ∼42,000 unique FGK-type stars in the catalog and show that the HETDEX spectra are sufficient to constrain these RVs with a 1σ precision of 28.0 km/s and bias of 3.5 km/s with respect to the LAMOST surveys and 1σ precision of 27.5 km/s and bias of 14.0 km/s compared to the SEGUE survey. Since these RVs are for faint (G≥16) stars, they will be complementary to Gaia. Using t-Distributed Stochastic Neighbor Embedding (t-SNE), we also demonstrate that the HETDEX spectra can be used to determine a star's Teff, and log g and its [Fe/H]. With the t-SNE projection of the FGK-type stars with HETDEX spectra we also identify 416 new candidate metal-poor ([Fe/H] <−1~dex) stars for future study. These encouraging results illustrate the utility of future low-resolution stellar spectroscopic surveys
The Massive and Distant Clusters of WISE Survey: MOO J1142+1527, a 10^(15) M_⊙ Galaxy Cluster at z = 1.19
We present confirmation of the cluster MOO J1142+1527, a massive galaxy cluster discovered as part of the Massive and Distant Clusters of WISE Survey. The cluster is confirmed to lie at z = 1.19, and using the Combined Array for Research in Millimeter-wave Astronomy we robustly detect the Sunyaev–Zel'dovich (SZ) decrement at 13.2σ. The SZ data imply a mass of M_(200m) = (1.1 ± 0.2) × 10^(15)M_⊙, making MOO J1142+1527 the most massive galaxy cluster known at z > 1.15 and the second most massive cluster known at z > 1. For a standard ΛCDM cosmology it is further expected to be one of the ~5 most massive clusters expected to exist at z ≥ 1.19 over the entire sky. Our ongoing Spitzer program targeting ~1750 additional candidate clusters will identify comparably rich galaxy clusters over the full extragalactic sky
The LIGO HET Response (LIGHETR) Project to Discover and Spectroscopically Follow Optical Transients Associated with Neutron Star Mergers
The LIGO HET Response (LIGHETR) project is an enterprise to follow up optical
transients (OT) discovered as gravitational wave merger sources by the
LIGO/Virgo collaboration (LVC). Early spectroscopy has the potential to
constrain crucial parameters such as the aspect angle. The LIGHETR
collaboration also includes the capacity to model the spectroscopic evolution
of mergers to facilitate a real-time direct comparison of models with our data.
The principal facility is the Hobby-Eberly Telescope. LIGHETR uses the
massively-replicated VIRUS array of spectrographs to search for associated OTs
and obtain early blue spectra and in a complementary role, the low-resolution
LRS-2 spectrograph is used to obtain spectra of viable candidates as well as a
densely-sampled series of spectra of true counterparts. Once an OT is
identified, the anticipated cadence of spectra would match or considerably
exceed anything achieved for GW170817 = AT2017gfo for which there were no
spectra in the first 12 hours and thereafter only roughly once daily. We
describe special HET-specific software written to facilitate the program and
attempts to determine the flux limits to undetected sources. We also describe
our campaign to follow up OT candidates during the third observational campaign
of the LIGO and Virgo Scientific Collaborations. We obtained VIRUS spectroscopy
of candidate galaxy hosts for 5 LVC gravitational wave events and LRS-2 spectra
of one candidate for the OT associated with S190901ap. We identified that
candidate, ZTF19abvionh = AT2019pip, as a possible Wolf-Rayet star in an
otherwise unrecognized nearby dwarf galaxy.Comment: 26 pages, 15 figure
TOI-5205b: A Jupiter transiting an M dwarf near the Convective Boundary
We present the discovery of TOI-5205b, a transiting Jovian planet orbiting a
solar metallicity M4V star, which was discovered using TESS photometry and then
confirmed using a combination of precise radial velocities, ground-based
photometry, spectra and speckle imaging. The host star TOI-5205 sits near the
eponymous `Jao gap', which is the transition region between partially and
fully-convective M dwarfs. TOI-5205b has one of the highest mass ratio for M
dwarf planets with a mass ratio of almost 0.3, as it orbits a host star
that is just . Its planetary radius is , while the mass is . Additionally, the large size
of the planet orbiting a small star results in a transit depth of ,
making it one of the deepest transits of a confirmed exoplanet orbiting a
main-sequence star. The large transit depth makes TOI-5205b a compelling target
to probe its atmospheric properties, as a means of tracing the potential
formation pathways. While there have been radial velocity-only discoveries of
giant planets around mid M dwarfs, this is the first transiting Jupiter with a
mass measurement discovered around such a low-mass host star. The high mass of
TOI-5205b stretches conventional theories of planet formation and disk scaling
relations that cannot easily recreate the conditions required to form such
planets.Comment: Submitted to ApJ. Comments are welcome. arXiv admin note: text
overlap with arXiv:2203.0717