Research

Topics of research 

  • The local environment of type Ia supernova host galaxies. I am using integral field spectroscopy data from PISCO and AMUSING to study whether the closest environment introdcues any effect in SN Ia brightness.
  • Type Ia SN cosmology in the near infrared. I am compiling NIR observations with ANDICAM and SOFI (ePESSTO) of a sample of very nearby (<40 Mpc) SNe Ia from the DLT40 survey and SNe Ia in the Hubble flow (z>0.01) to put constraints on the Hubble constant (H0) reducing uncertainties by a factor ~2.
  • Type II SN cosmology and forecasts. We are including high-z SNe II from DES in SN II Hubble diagram, and preparing forecasts for the LSST from simulations using different cadences.
  • Determination of the current local expansion rate of the Universe, the Hubble constant (H0). We are using near-infrared observations of nearby SNe Ia to reconstruct the panorama of our supercluster Laniakea. We will make accurate local measurements of H0 and the growth rate of cosmic structure parameterized by fσ8.

Finished projects

Mobirise

Müller-Bravo, Galbany, 2022, JOSS, 7(76):4508

HostPhot: global and local photometry of galaxies hosting supernovae or other transients

Type Ia supernovae (SNe Ia) have assumed a fundamental role as cosmological distance indicators since the discovery of the accelerating expansion rate of the universe. Correlations between their optical peak luminosity, the decline rate of their light curves and their optical colours allow them to be standardised, reducing their observed r.m.s scatter. Over a decade ago, the optical peak luminosity of SNe Ia was found to correlate with host galaxy stellar mass, further improving their standardisation. Since then, host galaxy properties have been used in cosmological analyses of SNe Ia and tremendous effort has gone into finding the property, such as star formation rate, that fundamentally drives the correlation between SNe Ia and their host galaxies. Furthermore, it has been noted that the local environment in which the progenitors of SNe Ia evolve is much better at reducing the scatter in estimated distances than the global environment, i.e., the whole galaxy. HostPhot is a tool that facilitates the calculation of both local and global photometry of galaxies hosting SNe Ia, therefore helping in the study of the environmental effect on these objects.

Mobirise

Galbany, de Jaeger, Riess, et al., 2022, A&A, submitted

An updated measurement of the Hubble constant from near-infrared observations of Type Ia supernovae

We present a measurement of the Hubble constant (H0) using type Ia supernova (SNe Ia) in the near-infrared (NIR) from the recently updated sample of SNe Ia in nearby galaxies with distances measured via Cepheid period-luminosity relations by the SHOES project. We collect public near-infrared photometry of up to 19 calibrator SNe Ia and further 57 SNe Ia in the Hubble flow (z>0.01), and directly measure their peak magnitudes in the J and H band by Gaussian processes and spline interpolation. Calibrator peak magnitudes together with Cepheid-based distances are used to estimate the average absolute magnitude in each band, while Hubble-flow SNe are used to constrain the zero-point intercept of the magnitude-redshift relation. Our baseline result of H0 is 72.3±1.4 (stat) ±1.4 (syst) km s−1 Mpc−1 in the J band and 72.3±1.3 (stat) ±1.4 (syst) km s−1 Mpc−1 in the H band, where the systematic uncertainties include the standard deviation of up to 21 variations of the analysis, the 0.7\% distance scale systematic from SHOES Cepheid anchors, a photometric zeropoint systematic, and a cosmic variance systematic. Our final measurement represents a measurement with a precision of 2.8\% in both bands. The variant with the largest change in H0 is when limiting the sample to SNe from CSP and CfA programmes, noteworthy because these are the best calibrated, yielding H0∼75 km s−1 Mpc−1 in both bands. We demonstrate stretch and reddening corrections are still useful in the NIR to standardize SN Ia NIR peak magnitudes. Based on our results, in order to improve the precision of the H0 measurement with SNe Ia in the NIR in the future, we would need to increase the number of calibrator SNe Ia, be able to extend the Hubble-Lemaître diagram to higher-z, and include standardization procedures to help reducing the NIR intrinsic scatter.

Mobirise

Müller-Bravo, Galbany, et al., A&A, 665, A123

Testing the homogeneity of Supernovae Ia in the NIR for accurate distance estimations

Since the discovery of the accelerating expansion of the Universe more than two decades ago, type Ia supernovae (SNe Ia) have been extensively used as standardizable candles in the optical. However, SNe Ia have shown to be more homogeneous in the near-infrared (NIR), where the effect of dust extinction is also attenuated. In this work, we explore the possibility of using a low number of NIR observations for accurate distance estimations, given the homogeneity at these wavelengths. We found that one epoch in J and/or H band, plus good gr-band coverage, gives an accurate estimation of Jmax and Hmax, and only introduces an additional scatter of ~0.04-0.05 mag for NIR epochs around optical peak. We also tested the effect of cadence and signal-to-noise ratio (S/N) in the estimation of tmax and its uncertainty propagation to the NIR peak magnitudes. The largest contribution comes from S/N, where we constrained the introduced scatter to <=0.02 mag in Jmax and <=0.01 in\Hmax, considering S/N values up to seven times smaller than the average from the reference sample. However, the effect of cadence and S/N are expected to be negligible, provided the data quality is comparable to that usually obtained for observations of nearby SNe (z<=0.1). These results provide confidence for our FLOWS project that aims in using SNe Ia with public ZTF optical light curves and few NIR epochs to map out the peculiar velocity field of the local Universe. This will allow us to determine the distribution of dark matter in our own supercluster, Laniakea, and test the standard cosmological model by measuring the growth rate of structures parameterized by fD and H0.

Mobirise

de Jaeger, Galbany, Riess, et al., 2022, MNRAS, submitted

A 5% measurement of the Hubble constant from Type II supernovae

The most stringent local measurement of the Hubble constant from Cepheid-calibrated Type Ia supernovae (SNe Ia) differs from the value inferred via the cosmic microwave background radiation (Planck+ΛCDM) by more than 5σ. This so-called "Hubble tension" has been confirmed by other independent methods, and thus does not appear to be a possible consequence of systematic errors. Here, we continue upon our prior work of using Type II supernovae to provide another, largely-independent method to measure the Hubble constant. From 13 SNe II with geometric, Cepheid, or tip of the red giant branch (TRGB) host-galaxy distance measurements, we derive H0=75.4+3.8−3.7 km s−1 Mpc−1 (statistical errors only), consistent with the local measurement but in disagreement by ~2.0σ with the Planck+ΛCDM value. Using only Cepheids (N=7), we find H0=77.6+5.2−4.8 km s−1 Mpc−1, while using only TRGB (N=5), we derive H0=73.1+5.7−5.3 km s−1 Mpc−1. Via 13 variants of our dataset, we derive a systematic uncertainty estimate of 1.5 km s−1 Mpc−1. The median value derived from these variants differs by just 0.3 km s−1 Mpc−1 from that produced by our fiducial model. Because we only replace SNe Ia with SNe II ---and we do not find tension between the Cepheid and TRGB H0 measurements--- our work reveals no indication that SNe Ia or Cepheids could be the sources of the "H0 tension". 

Funded by the Spanish Ministry of Science, Innovation and Universities (MICIU) project PID2020-115253GA-I00

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