Subjects: Astronomy >> Astrophysical processes submitted time 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
Abstract： 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 $4\%$.
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 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
Abstract： 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.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 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
Abstract： 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 $0.12
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Zhefu Yu
Paul Martini
A. Penton
T. M. Davis
C. S. Kochanek
G. F. Lewis
C. Lidman
U. Malik
R. Sharp
B. E. Tucker
M. Aguena
J. Annis
E. Bertin
S. Bocquet
D. Brooks
A. Carnero Rosell
D. Carollo
M. Carrasco Kind
J. Carretero
M. Costanzi
Abstract： The correlation between the broad line region radius and continuum luminosity ($R-L$ relation) of active galactic nuclei (AGN) is critical for single-epoch mass estimates of supermassive black holes (SMBHs). At $z \sim 1-2$, where AGN activity peaks, the $R-L$ relation is constrained by the reverberation mapping (RM) lags of the Mg II line. We present 25 Mg II lags from the Australian Dark Energy Survey (OzDES) RM project based on six years of monitoring. We define quantitative criteria to select good lag measurements and verify their reliability with simulations based on both the damped random walk stochastic model and the re-scaled, re-sampled versions of the observed lightcurves of local, well-measured AGN. Our sample significantly increases the number of Mg II lags and extends the $R-L$ relation to higher redshifts and luminosities. The relative iron line strength $\mathcal{R}_{\rm Fe}$ has little impact on the $R-L$ relation. The best-fit Mg II $R-L$ relation has a slope $\alpha = 0.39 \pm 0.08$ with an intrinsic scatter $\sigma_{\rm rl} = 0.15^{+0.03}_{-0.02}$. The slope is consistent with previous measurements and shallower than the H$\beta$ $R-L$ relation. The intrinsic scatter of the new $R-L$ relation is substantially smaller than previous studies and comparable to the intrinsic scatter of the H$\beta$ $R-L$ relation. Our new $R-L$ relation will enable more precise single-epoch mass estimates and SMBH demographic studies at cosmic noon.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 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
Abstract： 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 ($c<0$) and red ($c>0$) 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.
Peer Review Status:Awaiting Review
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