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.

Müller-Bravo, Galbany, Stritzinger, et al., 2025, A&A, accepted

Analyzing type Ia supernovae near-infrared light curves with Principal Component Analysis

Type Ia supernovae (SNeIa), the thermonuclear explosions of C/O white dwarf stars in binary systems, are phenomena that remain poorly understood. The complexity of their progenitor systems, explosion physics and intrinsic diversity poses not only challenges for their understanding as astrophysical objects, but also for their standardization and use as cosmological probes. Near-infrared (NIR) observations offer a promising avenue for studying the physics of SNeIa and for reducing systematic uncertainties in distance estimations, as they exhibit lower dust extinction and smaller dispersion in peak luminosity than optical bands. Here, Principal Component Analysis (PCA) is applied to a sample of SNeIa with well-sampled NIR (YJH-band) light curves to identify the dominant components of their variability and constrain physical underlying properties. The theoretical models of Kasen2006 are used for the physical interpretation of the PCA components, where we found the 56Ni mass to describe the dominant variability. Other factors, such as mixing and metallicity, were found to contribute significantly as well. However, some differences are found between the components of the NIR bands which may be attributed to differences in the explosion aspects they each trace. Additionally, the PCA components are compared to various light-curve parameters, identifying strong correlations between some components and peak brightness in both the NIR and optical bands, particularly in the Y band. When applying PCA to NIR color curves, we found interesting correlations with the host-galaxy mass, where SNeIa with redder NIR colors are predominantly found in less massive galaxies. We also investigate the potential for improved standardization in the Y band by incorporating PCA coefficients as correction parameters, leading to a reduction in the scatter of the intrinsic luminosity of SNeIa.

Burgaz, Maguire, Galbany, et al., 2025, A&A, accepted

ZTF SN Ia DR2 follow-up: Exploring the origin of the Type Ia supernova host galaxy step through Si II velocities

The relationship between Type Ia supernovae (SNe Ia) and their host galaxy stellar masses is well documented. In particular, Hubble residuals display a luminosity shift based on host mass, known as the mass step, which is often used as an extra correction in the standardisation of SN Ia luminosities. Here we investigate Hubble residuals and the mass step in the context of Si II λ6355 velocities, using 277 near-peak SNe Ia from ZTF DR2. We divide the sample into high-velocity (HV) and normal-velocity (NV) SNe Ia, separated at 12,000 km/s, resulting in 70 HV and 207 NV objects. We then examine links between Si II λ6355 velocities, light-curve stretch x1, colour c, and host properties to explore potential environmental and/or progenitor-related effects. Although we only find a marginal difference between the Hubble residuals of HV and NV SNe Ia, the NV mass step is 0.149±0.024 mag (6.3σ), while HV SNe Ia show 0.046±0.041 mag (1.1σ), consistent with zero. The NV-HV mass-step difference is ∼2.2σ. The clearest subtype difference is seen in central regions (dDLR<1), where NV SNe Ia show a strong mass step but HV SNe Ia none, yielding a 3.1−3.6σ difference. A host-colour step appears for both: NV 0.142±0.024 mag (5.9σ) and HV 0.158±0.042 mag (3.8σ). Overall, NV and HV colour steps are consistent. HV SNe Ia show modest (∼2.5-3σ) steps in outer regions (dDLR>1), while NV SNe show stronger environmental trends. Thus, NV SNe Ia appear more environmentally sensitive, especially in central, likely metal-rich and older regions, while HV SNe Ia show weaker, subset-dependent trends, and applying a universal mass-step correction could introduce biases. Refined classifications or environment-dependent factors may improve future cosmological analyses beyond standard x1 and c cuts.

González-Bañuleos, Gutiérrez, Galbany, et al., 2025, A&A, accepted

Statistical Analysis of Early Spectra in Type II and IIb Supernovae

We present a comprehensive analysis of the early spectra of type II and type IIb supernovae (SNe) to explore their diversity and distinguishable characteristics. Using 866 publicly available spectra from 393 SNe, 407 from type IIb SNe (SNe IIb) and 459 from type II SNe (SNe II), we analysed Hα
and He~I 5876 A at early phases (<40 days from the explosion) to identify possible differences between these two SN types. By comparing the pseudo-equivalent width (pEW) and full width at half maximum (FWHM), we find that the strength of the absorption component of these lines serves as a quantitative discriminator, with SNe IIb exhibiting stronger lines at all times. The most significant differences emerge within the first 10-20 days. To assess the statistical significance of these differences, we apply statistical methods and machine-learning techniques. Population density evolution reveals a clear distinction in both pEW and FWHM. Quadratic Discriminant Analysis confirms distinct evolutionary patterns, particularly in pEW, while FWHM variations are less pronounced. A combination of t-distributed Stochastic Neighbour Embedding and Linear Discriminant Analysis effectively separates the two SN types. Additionally, a Random Forest Classifier demonstrates the robustness of pEW and FWHM as classification criteria, allowing for accurate classification of newly observed SNe II and IIb based on computed classification probabilities. Applying our method to low-resolution spectra obtained from the Zwicky Transient Facility Bright Transient, a magnitude-limited survey, we identified 34 misclassified SNe. This revision increases the estimated fraction of SNe IIb from 4.0% to 7.26%. This finding suggests that misclassification significantly impacts the estimated core-collapse SN rate. Our approach enhances classification accuracy and provides a valuable tool for future supernova studies.

Kopsacheili, Anastasopoulou, Rea, et al., 2025, A&A, 701:A60

New X-ray supernova remnants in NGC 7793

Context. This work focuses on the detection of X-ray supernova remnants (SNRs) in the galaxy NGC 7793 and the study of their properties. Aims. X-ray SNRs in galaxies beyond the Local Group are rare, mainly due to the limited sensitivity of current X-ray instruments. Additionally, their identification requires an optical counterpart, making incomplete optical identification methods an extra challenge. Detecting X-ray SNRs in other galaxies is crucial to understanding their feedback in different evolutionary phases and gaining insights into their local interstellar medium (ISM). In NGC 7793, only one X-ray SNR was previously known, while a recent study reported nearly 240 optical SNRs. The discovery of a new, larger optical SNR sample motivated a re-examination of the X-ray SNR population by comparing optical SNRs with X-ray sources. Methods. To identify X-ray SNRs, we utilised Chandra's spatial resolution and analyzed all available archival data of NGC 7793, totaling 229.9 ks over 19 years. After data reduction, we performed source detection and analysis, searching for X-ray sources coinciding with optical SNRs. We also used XMM-Newton (1.1 Ms combined EPIC MOS) for a spectral analysis of the confirmed and candidate SNRs. Results. We detected 58 X-ray sources down to an observed luminosity of ∼9 × 1035 erg s‑1. Among them, five X-ray counterparts to optical SNRs were identified, all presenting soft emission (< 1.2 keV) with no short- or long-term variability. One corresponds to the previously known X-ray SNR, while four are newly detected. Spectral modelling of two SNRs shows thermal spectra exceeding 2.5 million K, with strong O VII, O VIII, and Ne IX emission lines. A correlation between density, X-ray luminosity, and source softness was observed. We also report X-ray emission from supernova 2008bk, refining its position, and suggest two candidate X-ray SNRs with soft, non-variable spectra, one resembling the identified X-ray SNRs.

Orellana, Bersten, Gutiérrez, 2025, A&A, 700:L17

SN 2022jli modeled with a 56Ni double layer and a magnetar

Context. We study the bolometric evolution of the exceptional Type Ic supernova SN 2022jli, aiming to understand the underlying mechanisms responsible for its distinctive double-peaked light curve morphology, extended timescales, and the rapid, steep decline in luminosity observed at around 270 days after the SN discovery. Aims. We present a quantitative assessment of two leading models through the use of hydrodynamic radiative simulations: two shells enriched with nickel and a combination of nickel and magnetar power. Methods. We explored the parameter space of a model in which the supernova (SN) is powered by radioactive decay while assuming a bimodal nickel distribution. Though this setup can reproduce the early light curve properties, it faces problems explaining the prominent second peak. We therefore considered a hybrid scenario with a rapidly rotating magnetar as an additional energy source. Results. We find that the observed light curve morphology can be well reproduced by a model combining a magnetar engine and a double-layer 56Ni distribution. The best-fitting case consists of a magnetar with a spin period of P ≃ 22 ms and a bipolar magnetic field strength of B ≃ 5 × 1014 G and a radioactive content with a total M(56Ni) of 0.15 M⊙ distributed across two distinct shells within a pre-SN structure of 11 M⊙. To reproduce the abrupt drop in luminosity at ∼270 d, the energy deposition from the magnetar must be rapidly and effectively switched off.

Galbany, Gutiérrez, Piscarreta, et al., 2025, JCAP, 8:53

Rapid follow-up observations of infant supernovae with the Gran Telescopio Canarias

The first few hours of a supernova (SN) contain significant information about the progenitor system. The most modern wide-field surveys that scan the sky repeatedly every few days can discover all kinds of transients in those early epochs. At such times, some progenitor footprints may be visible, elucidating critical explosion parameters and helping to distinguish between leading explosion models. A dedicated spectroscopic classification programme using the optical spectrograph OSIRIS mounted on the Gran Telescopio de Canarias was set up to try to obtain observations of supernovae (SNe) at those early epochs. With the time awarded, we obtained spectra of 10 SN candidates, which we present here. Half of them were thermonuclear SNe, while the other half were core-collapse SNe. Most (70%) were observed within the first six days of the estimated explosion, with two being captured within the first 48 hours. We present a characterization of the spectra, together with other public ancillary photometry from the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last Alert System (ATLAS). This project shows the need for an accompanying rapid-response spectroscopic programme for existing and future deep photometric wide-field surveys located at the right longitude to be able to trigger observations in a few hours after the discovery of the SN candidate. Both the future La Silla Southern Supernova Survey (LS4) and the Legacy Survey of Space and Time (LSST), both located in Chile, will be providing discovery and follow-up of most of the transients in the southern hemisphere. This paper demonstrates that with a rapid spectroscopic programme and stringent triggering criteria, obtaining a sample of SN with spectra within a day of the explosion is possible.

González-Gaitán, Gutiérrez, Martins, 2025, A&A, 700:119

Narrow absorption lines from intervening material in supernovae: II. Galaxy properties

The interstellar medium (ISM) has a number of tracers such as the NaI Dλλ 5890, 5896 absorption lines that are evident in the spectra of galaxies but also in those of individual astrophysical sources such as stars, novae, or quasars. Here, we investigate narrow absorption features in the spectra of nearby supernovae (SNe) and compare them to local (<0.5 kpc) and global host galaxy properties. With a large and heterogeneous sample of spectra, we are able to recover the known relations of ISM with galaxy properties: larger columns of ISM gas are found in environments that are more massive, more actively star-forming, younger, and viewed from a more inclined angle. Most trends are stronger for local properties than global properties, and we find that the ISM column density decreases exponentially with the offset from the host galaxy centre, as expected for a gas distribution following an exponential radial profile. We also confirm trends for the velocity of galactic outflows increasing with radius. The current study demonstrates the capability of individual light sources to serve as ubiquitous tracers of ISM properties across various environments and galaxies.

Gutiérrez, Mattila, Lundqvist, et al., 2025, ApJ, 977:162

CSS 161010: A Luminous Fast Blue Optical Transient with Broad Blueshifted Hydrogen Lines

We present ultraviolet, optical, and near-infrared photometric and optical spectroscopic observations of the luminous fast blue optical transient (LFBOT) CSS 161010:045834–081803 (CSS 161010). The transient was found in a low-redshift (z = 0.033) dwarf galaxy. The light curves of CSS 161010 are characterized by an extremely fast evolution and blue colors. The V-band light curve shows that CSS 161010 reaches an absolute peak of mag in 3.8 days from the start of the outburst. After maximum, CSS 161010 follows a power-law decline ∝t ‑2.8±0.1 in all optical bands. These photometric properties are comparable to those of well-observed LFBOTs such as AT 2018cow, AT 2020mrf, and AT 2020xnd. However, unlike these objects, the spectra of CSS 161010 show a remarkable transformation from a blue and featureless continuum to spectra dominated by very broad, entirely blueshifted hydrogen emission lines with velocities of up to 10% of the speed of light. The persistent blueshifted emission and the lack of any emission at the rest wavelength of CSS 161010 are unique features not seen in any transient before CSS 161010. The combined observational properties of CSS 161010 and its M * ∼ 108 M ⊙ dwarf galaxy host favor the tidal disruption of a star by an intermediate-mass black hole as its origin.

González-Díaz, Rosales-Ortega, Galbany, 2024, A&A, 691:25

Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS): II. Revisiting the ionisation mechanism of the extraplanar diffuse ionised gas

The extraplanar diffuse ionised gas (eDIG) is a key component for understanding the feedback processes that connect galactic discs and their halos. In this paper, we present the second study of the Bidimensional Exploration of the warm-Temperature Ionised Gas (BETIS) project, the aim of which is to explore the possible ionisation mechanisms and characteristics of the eDIG. We use a sample of eight edge-on galaxies observed with the Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph (IFS) and apply the methodology developed in the first paper of the BETIS project for obtaining binned emission line maps. We find that the vertical and radial profiles of the [N II]/Hα, [S II]/Hα, [O III]/Hβ, and [O I]/Hα ratios depict a complex ionisation structure within galactic halos – which is influenced by the spatial distribution of H II regions across the galactic plane as observed from our line of sight–, with Lyman continuum photon leakage from OB associations constituting the main ionisation source. Moreover, the electron temperature and S+/S ionisation ratio also exhibit a dependency on the distribution of H II regions within the galactic discs. Our analysis excludes low-mass, hot, and evolved stars (HOLMES) as viable candidates for secondary ionisation sources to elucidate the unusual behaviour of the line ratios at greater distances from the galactic midplane. In contrast, we ascertain that shocks induced in the interstellar medium by star formation(SF)-related feedback mechanisms represent a promising secondary ionisation source of the eDIG. We present a suite of models integrating ionisation mechanisms arising from fast shocks and photoionisation associated with star formation. When applied to the classical Baldwin–Phillips–Terlevich (BPT) diagrams, these models reveal that the ionisation budget of the eDIG ranges from 20% to 50% across our sample, with local variations of up to 20% within individual galaxy halos. This contribution correlates with the presence of filaments and other structural components observed within galaxy halos. The presence of shocks is additionally supported by the observation of a high density of high [O I]/Hα ratios, which is characteristic of shock-compressed ionised gas, and is likely induced by feedback from regions of intense SF within the galactic disc. These results demonstrate consistency across all galaxies analysed in this sample.

González-Gaitán, Gutiérrez, Anderson, et al., 2024, A&A, 687:108

Narrow absorption lines from intervening material in supernovae. I. Measurements and temporal evolution

Narrow absorption features in nearby supernova (SN) spectra are a powerful diagnostic of the slow-moving material in the line of sight: they are extensively used to infer dust extinction from the host galaxies, and they can also serve in the detection of circumstellar material originating from the SN progenitor and present in the vicinity of the explosion. Despite their wide use, very few studies have examined the biases of the methods to characterize narrow lines, and not many statistical analyses exist. This is the first paper of a series in which we present a statistical analysis of narrow lines of SN spectra of various resolutions. We developed a robust automated methodology to measure the equivalent width (EW) and velocity of narrow absorption lines from intervening material in the line of sight of SNe, including Na I D, Ca II H&K, K I, and diffuse interstellar bands. We carefully studied systematic biases in heterogeneous spectra from the literature by simulating different signal-to-noise, spectral resolution, size and orientation of the slit, and we present the real capabilities and limitations of using low- and mid-resolution spectra to study these lines. In particular, we find that the measurement of the EW of the narrow lines in low-resolution spectra is highly affected by the evolving broad P-Cygni profiles of the SN ejecta, both for core-collapse and type Ia SNe, inducing a conspicuous apparent evolution. Such pervading non-physical evolution of narrow lines might lead to wrong conclusions on the line-of-sight material, for example concerning circumstellar material ejected from the SN progenitors. We thus present an easy way to detect and exclude those cases to obtain more robust and reliable measurements. Finally, after considering all possible effects, we analysed the temporal evolution of the narrow features in a large sample of nearby SNe to detect any possible variation in their EWs over time. We find no time evolution of the narrow line features in our large sample for all SN types.

González-Díaz, Rosales-Ortega, Galbany, et al., 2024, A&A, 687:A20

Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS). I. Showcase sample and first results

We present the Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS) project, designed for the spatial and spectral study of the diffuse ionised gas (DIG) in a selection of nearby spiral galaxies observed with the MUSE integral-field spectrograph. Our primary objective is to investigate the various ionisation mechanisms at play within the DIG. We analysed the distribution of high- and low-ionisation species in the optical spectra of the sample on a spatially resolved basis. We introduced a new methodology for spectroscopically defining the DIG, optimised for galaxies of different resolutions. Our analysis of the showcase sample reveals a consistent cumulative DIG fraction across all galaxies in the sample, averaging around 40%-70%. The average radial distribution of the [N II]/Hα, [S II]/Hα, [O I]/Hα, and [O III]/Hβ ratios are enhanced in the DIG regimes (up to 0.2 dex). It follows similar trends between the DIG regime and the H II regions, as well as the Hα surface brightness (ΣHα), indicating a correlation between the ionisation of these species in both the DIG and the H II regions. The DIG loci in typical diagnostic diagrams are found, in general, within the line ratios that correspond to photoionisation due to the star formation. There is a noticeable offset correspondent to ionisation due to fast shocks. However, an individual diagnosis performed for each galaxy reveals that all the DIG in these galaxies can be attributed to photoionisation from star formation. The offset is primarily due to the contribution of Seyfert galaxies in our sample, which is closely aligned with models of ionisation from fast shocks and galactic outflows, thus mimicking the DIG emission. Our results indicate that galaxies exhibiting active galactic nucleus (AGN) activity should be considered separately when conducting a general analysis of the DIG ionisation mechanisms, since this emission is indistinguishable from high-excitation DIG.

Dessart, Gutiérrez, Ercolino, et al., 2024, A&A, 685:A169

A sequence of Type Ib, IIb, II-L, and II-P supernovae from binary-star progenitors with varying initial separations

Over the last decade, evidence has accumulated that massive stars do not typically evolve in isolation but instead follow a tumultuous journey with a companion star on their way to core collapse. While Roche-lobe overflow appears instrumental for the production of a large fraction of Type Ib and Ic supernovae (SNe), variations in the initial orbital period, Pinit, of massive interacting binaries may also produce a wide diversity of case B, BC, or C systems, with pre-SN stars endowed from minute to massive H-rich envelopes. Focusing here on the explosion of the primary donor star, originally 12.6 M⊙, we used radiation hydrodynamics and nonlocal thermodynamic equilibrium time-dependent radiative transfer to document the gas and radiation properties of such SNe, covering Types Ib, IIb, II-L, and II-P. Variations in Pinit are the root cause of the wide diversity of our SN light curves, which present single-peak, double-peak, fast-declining, or plateau-like morphologies in the V band. The different ejecta structures, expansion rates, and relative abundances (e.g., H, He, and 56Ni) can lead to a great deal of diversity in terms of spectral line shapes (absorption versus emission strength and width) and evolution. We emphasize that Hα is a key tracer of these modulations, and that He I 7065 Å is an enduring optical diagnostic for the presence of He. Our grid of simulations fares well against representative Type Ib, IIb, and II-P SNe, but interaction with circumstellar material, which is ignored in this work, is likely at the origin of the tension between our Type II-L SN models and observations (e.g., of SN 2006Y). Remaining discrepancies in the rise time to bolometric maximum of our models call for a proper account of both small-scale and large-scale structures in core-collapse SN ejecta. Discrepant Type II-P SN models, with a high plateau brightness but small spectral line widths, can be fixed by adopting more compact red-supergiant star progenitors.

Kopsacheili, Jiménez-Palau, Galbany, et al., 2024, MNRAS, 530:1078

Supernova remnant properties and luminosity functions in NGC 7793 using MUSE IFS

In this study, we use MUSE Integral Field Spectroscopy (IFS), along with multiline diagnostics, for the optical identification of supernova remnants (SNRs) in the galaxy NGC 7793. We find in total 238 SNR candidates, 225 of them new identifications, increasing significantly the number of known SNRs in this galaxy. The velocity dispersion of the candidate SNRs was calculated, giving a mean value of 27kms−1. We construct the Hα, [S II], [O III], and [S II]-Hα luminosity functions, and for the first time, the [N II], [N II]-Hα, [N II]-[S II], [O III]-[S II], and [O III]-[N II] luminosity functions of the candidate SNRs. Shock models, along with the observed multiline information were used, in order to estimate shock velocities. The ∼65% of the SNRs present velocities < 300 kms−1. There is a clear correlation between shock velocity and [O III]/Hβ ratio, and a less clear but still evident correlation in the relation between shock velocity and the [S II]/Hα, [N II]/Hα ratios. We also use the [S II]6716/31 ratio of the SNR candidates to calculate their post-shock density, assuming different temperatures. The median value of the density of our sample is ∼80cm−3, for a temperature of T=104K. No correlation between shock velocity and density, or density and SNRs with [S II]/Hα> 0.4 and [S II]/Hα< 0.4 is observed.

Kim, Galbany, Hook, Kang, 2024, MNRAS, 529:3806

Tracing back the birth environments of Type Ia supernova progenitor stars: a pilot study based on 44 early-type host galaxies

The environmental dependence of Type Ia supernova (SN Ia) luminosities is well established, and efforts are being made to find its origin. Previous studies typically use the currently observed status of the host galaxy. However, given the delay time between the birth of the progenitor star and the SN Ia explosion, the currently observed status may differ from the birth environment of the SN Ia progenitor star. In this paper, employing the chemical evolution and accurately determined stellar population properties of 44 early-type host galaxies, we, for the first time, estimate the SN Ia progenitor star birth environment, specifically [Fe/H]Birth and [α/Fe]Birth. We show that [α/Fe]Birth has a 30.4+10.6−10.1 per cent
wider range than the currently observed [α/Fe]Current, while the range of [Fe/H]Birth is not statistically different ( 17.9+26.0−27.1 per cent) to that of [Fe/H]Current. The birth and current environments of [Fe/H] and [α/Fe] are sampled from different populations (p-values of the Kolmogorov-Smirnov test <0.01). We find that light-curve fit parameters are insensitive to [Fe/H]Birth (<0.9σ for the non-zero slope), while a linear trend is observed with Hubble residuals (HRs) at the 2.4σ significance level. With [α/Fe]Birth, no linear trends (<1.1σ) are observed. Interestingly, we find that [α/Fe]Birth clearly splits the SN Ia sample into two groups: SN Ia exploded in [α/Fe]Birth-rich or [α/Fe]Birth-poor environments. SNe Ia exploded in different [α/Fe]Birth groups have different weighted-means of light-curve shape parameters: 0.81 ± 0.33 (2.5σ). They are thought to be drawn from different populations (p-value = 0.01). Regarding SN Ia colour and HRs, there is no difference (<1.0σ) in the weighted-means and distribution (p-value > 0.27) of each [α/Fe]Birth group.

González-Díaz, Galbany, Kangas, et al., 2024, A&A, 684:A104

Supernova environments in J-PLUS. Normalized cumulative-rank distributions and stellar-population synthesis combining narrow- and broad-band filters

We investigated the local environmental properties of 418 supernovae (SNe) of all types using data from the Javalambre Photometric Local Universe Survey (J-PLUS), which includes five broad-band and seven narrow-band imaging filters. Our study involves two independent analyses: (1) the normalized cumulative-rank (NCR) method, which utilizes all 12 single bands along with five continuum-subtracted narrow-band emission and absorption bands, and (2) simple stellar population (SSP) synthesis, where we build spectral energy distributions (SED) of the surrounding 1 kpc2 SN environment using the 12 broad- and narrow-band filters. The main difference is that type Ia, II, and IIb SNe are preferably located in redder environments than the other SN types. The radial distribution of the SNe shows that type IIb SNe seem to have a preference for occurring in the inner regions of galaxies, whereas other types of SNe occur throughout the galaxies without a distinct preference for a specific location. For the Hα filter we recover the sequence from SNe Ic, which has the highest NCR, to SNe Ia, which has the lowest; this is interpreted as a sequence in progenitor mass and age. All core-collapse SN types are strongly correlated to the [O II] emission, which also traces star formation rate (SFR), following the same sequence as in Hα. The NCR distributions of the Ca II triplet show a clear division between II-IIb-Ia and Ib-Ic-IIn subtypes, which is interpreted as a difference in the environmental metallicity. Regarding the SSP synthesis, we found that including the seven J-PLUS narrow filters in the fitting process has a more significant effect on the core-collapse SN environmental parameters than for SNe Ia, shifting their values toward more extincted, younger, and more star-forming environments, due to the presence of strong emission lines and stellar absorptions in those narrow bands.

Martínez-Rodríguez, Galbany, Badenes, et al., 2024, ApJ, 963:125

Recovering Lost Light: Discovery of Supernova Remnants with Integral Field Spectroscopy

We present results from a systematic search for broad (≥ 400 km s‑1) Hα emission in integral field spectroscopy data cubes of ∼1200 nearby galaxies obtained with PMAS and MUSE. We found 19 unique regions that pass our quality cuts, four of which match the locations of previously discovered supernovae (SNe): one Type IIP and three Type IIn, including the well-known SN 2005ip. We suggest that these objects are young Supernova remnants (SNRs), with bright and broad Hα emission powered by the interaction between the SN ejecta and dense circumstellar material. The stellar ages measured at the locations of these SNR candidates are systematically lower by about 0.5 dex than those measured at the locations of core-collapse (CC) SNe, implying that their progenitors might be shorter lived and therefore more massive than a typical CCSN progenitor. The methods laid out in this work open a new window into the study of nearby SNe with integral field spectroscopy.

Sánchez, Galbany, Walcher, et al., 2023, MNRAS, 526:5555

The Calar Alto Legacy Integral Field Area survey: extended and remastered data release

This paper describes the extended data release (eDR) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It comprises science-grade quality data for 895 galaxies obtained with the Potsdam Multi Aperture Spectograph/PPak instrument at the 3.5-m telescope at the Calar Alto Observatory along the last 12 yr, using the V500 setup [3700-7500 Å, 6 Å/full-width at half-maximum (FWHM)] and the CALIFA observing strategy. It includes galaxies of any morphological type, star formation stage, a wide range of stellar masses (~107-1012 M⊙), at an average redshift of ~0.015 (90 per cent within 0.005 < z < 0.05). Primarily selected based on the projected size and apparent magnitude, we demonstrate that it can be volume corrected resulting in a statistically limited but representative sample of the population of galaxies in the nearby Universe. All the data were homogeneous re-reduced, introducing a set of modifications to the previous reduction. The most relevant is the development and implementation of a new cube-reconstruction algorithm that provides with an (almost) seeing-limited spatial resolution (FWHMPSF ~ 1.0 arcsec). To illustrate the usability and quality of the data, we extracted two aperture spectra for each galaxy (central 1.5 arcsec and fully integrated), and analyse them using PYFIT3D. We obtain a set of observational and physical properties of both the stellar populations and the ionized gas, that have been compared for the two apertures, exploring their distributions as a function of the stellar masses and morphologies of the galaxies, comparing with recent results in the literature.

Galbany, de Jaeger, Riess, et al., 2023, A&A, 679:A95

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.

Moriya, Galbany, Jiménez-Palau, et al., 2023, A&A, 677:A20

Environmental dependence of Type IIn supernova properties

Type IIn supernovae occur when stellar explosions are surrounded by dense hydrogen-rich circumstellar matter. The dense circumstellar matter is likely formed by extreme mass loss from their progenitors shortly before they explode. The nature of Type IIn supernova progenitors and the mass-loss mechanism forming the dense circumstellar matter are still unknown. In this work, we investigate whether Type IIn supernova properties and their local environments are correlated. We use Type IIn supernovae with well-observed light curves and host-galaxy integral field spectroscopic data so that we can estimate both supernova and environmental properties. We find that Type IIn supernovae with a higher peak luminosity tend to occur in environments with lower metallicity and/or younger stellar populations. The circumstellar matter density around Type IIn supernovae is not significantly correlated with metallicity, so the mass-loss mechanism forming the dense circumstellar matter around Type IIn supernovae might be insensitive to metallicity.

de Jaeger, Galbany, Riess, et al., 2022, MNRAS, 514:4620

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".

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.

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.

Galbany, Smith, Duarte Puertas, et al., 2022, A&A, 659:A89

Aperture-corrected spectroscopic type Ia supernova host galaxy properties

We use type Ia supernova (SN Ia) data obtained by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SNS) in combination with the publicly available SDSS DR16 fiber spectroscopy of supernova (SN) host galaxies to correlate SN Ia light-curve parameters and Hubble residuals with several host galaxy properties. Fixed-aperture fiber spectroscopy suffers from aperture effects: the fraction of the galaxy covered by the fiber varies depending on its projected size on the sky, and thus measured properties are not representative of the whole galaxy. The advent of integral field spectroscopy has provided a way to correct the missing light, by studying how these galaxy parameters change with the aperture size. Here we study how the standard SN host galaxy relations change once global host galaxy parameters are corrected for aperture effects. We recover previous trends on SN Hubble residuals with host galaxy properties, but we find that discarding objects with poor fiber coverage instead of correcting for aperture loss introduces biases into the sample that affect SN host galaxy relations. The net effect of applying the commonly used g-band fraction criterion is that intrinsically faint SNe Ia in high-mass galaxies are discarded, thus artificially increasing the height of the mass step by 0.02 mag and its significance. Current and next-generation fixed-aperture fiber-spectroscopy surveys, such as OzDES, DESI, or TiDES with 4MOST, that aim to study SN and galaxy correlations must consider, and correct for, these effects.