分类： 天文学 >> 天文学 提交时间： 2023-02-19
C. R. Bom
J. Annis
A. Garcia
A. Palmese
N. Sherman
M. Soares-Santos
L. Santana-Silva
R. Morgan
K. Bechtol
T. Davis
H. T. Diehl
S. S. Allam
T. G. Bachmann
B. M. O. Fraga
J. Garcıa-Bellido
M. S. S. Gill
K. Herner
C. D. Kilpatrick
M. Makler
F. Olivares E.
摘要： We address the problem of optimally identifying all kilonovae detected via gravitational wave emission in the upcoming LIGO/Virgo/KAGRA Collaboration observing run, O4, which is expected to be sensitive to a factor of $\sim 7$ more Binary Neutron Stars alerts than previously. Electromagnetic follow-up of all but the brightest of these new events will require $>1$ meter telescopes, for which limited time is available. We present an optimized observing strategy for the Dark Energy Camera during O4. We base our study on simulations of gravitational wave events expected for O4 and wide-prior kilonova simulations. We derive the detectabilities of events for realistic observing conditions. We optimize our strategy for confirming a kilonova while minimizing telescope time. For a wide range of kilonova parameters, corresponding to a fainter kilonova compared to GW170817/AT2017gfo we find that, with this optimal strategy, the discovery probability for electromagnetic counterparts with the Dark Energy Camera is $\sim 80\%$ at the nominal binary neutron star gravitational wave detection limit for the next LVK observing run (190 Mpc), which corresponds to a $\sim 30\%$ improvement compared to the strategy adopted during the previous observing run. For more distant events ($\sim 330$ Mpc), we reach a $\sim 60\%$ probability of detection, a factor of $\sim 2$ increase. For a brighter kilonova model dominated by the blue component that reproduces the observations of GW170817/AT2017gfo, we find that we can reach $\sim 90\%$ probability of detection out to 330 Mpc, representing an increase of $\sim 20 \%$, while also reducing the total telescope time required to follow-up events by $\sim 20\%$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Umang Malik
Rob Sharp
A. Penton
Z. Yu
P. Martini
C. Lidman
B. E. Tucker
T. M. Davis
G. F. Lewis
M. Aguena
S. Allam
O. Alves
F. Andrade-Oliveira
J. Asorey
D. Bacon
E. Bertin
S. Bocquet
D. Brooks
D. L. Burke
A. Carnero Rosell
摘要： Reverberation mapping measurements have been used to constrain the
relationship between the size of the broad-line region and luminosity of active
galactic nuclei (AGN). This $R-L$ relation is used to estimate single-epoch
virial black hole masses, and has been proposed for use to standardise AGN to
determine cosmological distances. We present reverberation measurements made
with H$\beta$ from the six-year Australian Dark Energy Survey (OzDES)
Reverberation Mapping Program. We successfully recover reverberation lags for
eight AGN at $0.12
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zhefu Yu
Paul Martini
A. Penton
T. M. Davis
U. Malik
C. Lidman
B. E. Tucker
R. Sharp
C. S. Kochanek
B. M. Peterson
M. Aguena
S. Allam
F. Andrade-Oliveira
J. Annis
J. Asorey
E. Bertin
D. Brooks
D. L. Burke
J. Calcino
A. Carnero Rosell
摘要： Reverberation mapping is a robust method to measure the masses of supermassive black holes (SMBHs) outside of the local Universe. Measurements of the radius -- luminosity ($R-L$) relation using the Mg II emission line are critical for determining these masses near the peak of quasar activity at $z \approx 1 - 2$, and for calibrating secondary mass estimators based on Mg II that can be applied to large samples with only single-epoch spectroscopy. We present the first nine Mg II lags from our five-year Australian Dark Energy Survey (OzDES) reverberation mapping program, which substantially improves the number and quality of Mg II lag measurements. As the Mg II feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multi-epoch spectra before analyzing the Mg II line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H$\beta$ and Mg II $R-L$ relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4\%$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
M. Dixon
C. Lidman
J. Mould
L. Kelsey
D. Brout
A. Möller
P. Wiseman
M. Sullivan
L. Galbany
T. M. Davis
M. Vincenzi
D. Scolnic
G. F. Lewis
M. Smith
R. Kessler
A. Duffy
E. Taylor
C. Flynn
T. M. C. Abbott
M. Aguena
摘要： We use stacked spectra of the host galaxies of photometrically identified type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) to search for correlations between Hubble diagram residuals and the spectral properties of the host galaxies. Utilising full spectrum fitting techniques on stacked spectra binned by Hubble residual, we find no evidence for trends between Hubble residuals and properties of the host galaxies that rely on spectral absorption features ($< 1.3\sigma$), such as stellar population age, metallicity, and mass-to-light ratio. However, we find significant trends between the Hubble residuals and the strengths of [OII] ($4.4\sigma$) and the Balmer emission lines ($3\sigma$). These trends are weaker than the well known trend between Hubble residuals and host galaxy stellar mass ($7.2\sigma$) that is derived from broad band photometry. After light curve corrections, we see fainter SNe Ia residing in galaxies with larger line strengths. We also find a trend (3$\sigma$) between Hubble residual and the Balmer decrement (a measure of reddening by dust) using H${\beta}$ and H${\gamma}$. The trend, quantified by correlation coefficients, is slightly more significant in the redder SNe Ia, suggesting that bluer SNe Ia are relatively unaffected by dust in the interstellar medium of the host and that dust contributes to current Hubble diagram scatter impacting the measurement of cosmological parameters.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. Sánchez
Y. Omori
C. Chang
L. E. Bleem
T. Crawford
A. Drlica-Wagner
S. Raghunathan
G. Zacharegkas
T. M. C. Abbott
M. Aguena
A. Alarcon
S. Allam
O. Alves
A. Amon
S. Avila
E. Baxter
K. Bechtol
B. A. Benson
G. M. Bernstein
E. Bertin
摘要： We cross-correlate positions of galaxies measured in data from the first three years of the Dark Energy Survey with Compton-$y$-maps generated using data from the South Pole Telescope (SPT) and the {\it Planck} mission. We model this cross-correlation measurement together with the galaxy auto-correlation to constrain the distribution of gas in the Universe. We measure the hydrostatic mass bias or, equivalently, the mean halo bias-weighted electron pressure $\langle b_{h}P_{e}\rangle$, using large-scale information. We find $\langle b_{h}P_{e}\rangle$ to be $[0.16^{+0.03}_{-0.04},0.28^{+0.04}_{-0.05},0.45^{+0.06}_{-0.10},0.54^{+0.08}_{-0.07},0.61^{+0.08}_{-0.06},0.63^{+0.07}_{-0.08}]$ meV cm$^{-3}$ at redshifts $z \sim [0.30, 0.46, 0.62,0.77, 0.89, 0.97]$. These values are consistent with previous work where measurements exist in the redshift range. We also constrain the mean gas profile using small-scale information, enabled by the high-resolution of the SPT data. We compare our measurements to different parametrized profiles based on the cosmo-OWLS hydrodynamical simulations. We find that our data are consistent with the simulation that assumes an AGN heating temperature of $10^{8.5}$K but are incompatible with the model that assumes an AGN heating temperature of $10^{8.0}$K. These comparisons indicate that the data prefer a higher value of electron pressure than the simulations within $r_{500c}$ of the galaxies' halos.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
C. Zhou
A. Tong
M. A. Troxel
J. Blazek
C. Lin
D. Bacon
L. Bleem
A. Carnero Rosell
C. Chang
M. Costanzi
J. DeRose
J. P. Dietrich
A. Drlica-Wagner
D. Gruen
R. A. Gruendl
B. Hoyle
M. Jarvis
N. MacCrann
B. Mawdsley
T. McClintock
摘要： Clusters of galaxies are sensitive to the most nonlinear peaks in the cosmic density field. The weak gravitational lensing of background galaxies by clusters can allow us to infer their masses. However, galaxies associated with the local environment of the cluster can also be intrinsically aligned due to the local tidal gradient, contaminating any cosmology derived from the lensing signal. We measure this intrinsic alignment in Dark Energy Survey (DES) Year 1 redMaPPer clusters. We find evidence of a non-zero mean radial alignment of galaxies within clusters between redshift 0.1-0.7. We find a significant systematic in the measured ellipticities of cluster satellite galaxies that we attribute to the central galaxy flux and other intracluster light. We attempt to correct this signal, and fit a simple model for intrinsic alignment amplitude ($A_{\textrm{IA}}$) to the measurement, finding $A_{\textrm{IA}}=0.15\pm 0.04$, when excluding data near the edge of the cluster. We find a significantly stronger alignment of the central galaxy with the cluster dark matter halo at low redshift and with higher richness and central galaxy absolute magnitude (proxies for cluster mass). This is an important demonstration of the ability of large photometric data sets like DES to provide direct constraints on the intrinsic alignment of galaxies within clusters. These measurements can inform improvements to small-scale modeling and simulation of the intrinsic alignment of galaxies to help improve the separation of the intrinsic alignment signal in weak lensing studies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. Myles
D. Gruen
A. Amon
A. Alarcon
J. DeRose
S. Everett
S. Dodelson
G. M. Bernstein
A. Campos
I. Harrison
N. MacCrann
J. McCullough
M. Raveri
C. Sánchez
M. A. Troxel
B. Yin
T. M. C. Abbott
S. Allam
O. Alves
F. Andrade-Oliveira
摘要： We present a method for mapping variations between probability distribution functions and apply this method within the context of measuring galaxy redshift distributions from imaging survey data. This method, which we name PITPZ for the probability integral transformations it relies on, uses a difference in curves between distribution functions in an ensemble as a transformation to apply to another distribution function, thus transferring the variation in the ensemble to the latter distribution function. This procedure is broadly applicable to the problem of uncertainty propagation. In the context of redshift distributions, for example, the uncertainty contribution due to certain effects can be studied effectively only in simulations, thus necessitating a transfer of variation measured in simulations to the redshift distributions measured from data. We illustrate the use of PITPZ by using the method to propagate photometric calibration uncertainty to redshift distributions of the Dark Energy Survey Year 3 weak lensing source galaxies. For this test case, we find that PITPZ yields a lensing amplitude uncertainty estimate due to photometric calibration error within 1 per cent of the truth, compared to as much as a 30 per cent underestimate when using traditional methods.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
L. Kelsey
M. Sullivan
P. Wiseman
P. Armstrong
R. Chen
D. Brout
T. M. Davis
M. Dixon
C. Frohmaier
L. Galbany
O. Graur
R. Kessler
C. Lidman
A. Möller
B. Popovic
B. Rose
D. Scolnic
M. Smith
M. Vincenzi
T. M. C. Abbott
摘要： Recent analyses have found intriguing correlations between the colour ($c$) of type Ia supernovae (SNe Ia) and the size of their 'mass-step', the relationship between SN Ia host galaxy stellar mass ($M_\mathrm{stellar}$) and SN Ia Hubble residual, and suggest that the cause of this relationship is dust. Using 675 photometrically-classified SNe Ia from the Dark Energy Survey 5-year sample, we study the differences in Hubble residual for a variety of global host galaxy and local environmental properties for SN Ia subsamples split by their colour. We find a $3\sigma$ difference in the mass-step when comparing blue ($c0$) SNe. We observe the lowest r.m.s. scatter ($\sim0.14$ mag) in the Hubble residual for blue SNe in low mass/blue environments, suggesting that this is the most homogeneous sample for cosmological analyses. By fitting for $c$-dependent relationships between Hubble residuals and $M_\mathrm{stellar}$, approximating existing dust models, we remove the mass-step from the data and find tentative $\sim 2\sigma$ residual steps in rest-frame galaxy $U-R$ colour. This indicates that dust modelling based on $M_\mathrm{stellar}$ may not fully explain the remaining dispersion in SN Ia luminosity. Instead, accounting for a $c$-dependent relationship between Hubble residuals and global $U-R$, results in $\leq1\sigma$ residual steps in $M_\mathrm{stellar}$ and local $U-R$, suggesting that $U-R$ provides different information about the environment of SNe Ia compared to $M_\mathrm{stellar}$, and motivating the inclusion of galaxy $U-R$ colour in SN Ia distance bias correction.
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