arXiv subjects

L. Galbany

Publications and source records attributed to L. Galbany.

At least 163 records · Page 9Linked to original sources

arXiv2022

Cosmological Results from the RAISIN Survey: Using Type Ia Supernovae in the Near Infrared as a Novel Path to Measure the Dark Energy Equation of State

Type Ia supernovae (SNe Ia) are more precise standardizable candles when measured in the near-infrared (NIR) than in the optical. With this motivation, from 2012-2017 we embarked on the RAISIN program with the Hubble Space Telescope (HST) to obtain rest-frame NIR light curves for a cosmologically distant sample of 37 SN Ia ($0.2 \lesssim z \lesssim 0.6$) discovered by Pan-STARRS and the Dark Energy Survey. By comparing higher-$z$ HST data with 42 SN Ia at $z<0.1$ observed in the NIR by the Carnegie Supernova Project, we construct a Hubble diagram from NIR observations (with only time of maximum light and some selection cuts from optical data) to pursue a unique avenue to constrain the dark energy equation of state parameter, $w$. We analyze the dependence of the full set of Hubble residuals on the SN Ia host galaxy mass and find Hubble residual steps of size $\sim$0.06-0.1~mag with 1.5- to 2.5-$σ$ significance depending on the method and step location. Combining our NIR sample with CMB constraints, we find $1+w=-0.17\pm0.12$ (stat$+$syst). The largest systematic errors are the redshift-dependent SN selection biases and the properties of the NIR mass step. We also use these data to measure $H_0=75.9\pm 2.2$ km s$^{-1}$ Mpc$^{-1}$ from stars with geometric distance calibration in the hosts of 8 SNe Ia observed in the NIR versus $H_0=71.2\pm3.8$ km s$^{-1}$ Mpc$^{-1}$ using an inverse distance ladder approach tied to Planck. Using optical data we find $1+w=-0.10\pm0.09$ and with optical and NIR data combined, we find $1+w=-0.06\pm0.07$; these shifts of up to 0.11 in $w$ could point to inconsistency in optical versus NIR SN models. There will be many opportunities to improve this NIR measurement and better understand systematic uncertainties through larger low-$z$ samples, new light-curve models, calibration improvements, and by building high-$z$ samples from the Roman Space Telescope.

astro-ph.CO↗

arXiv2022

The Dark Energy Survey 5-year photometrically identified Type Ia Supernovae

As part of the cosmology analysis using Type Ia Supernovae (SN Ia) in the Dark Energy Survey (DES), we present photometrically identified SN Ia samples using multi-band light-curves and host galaxy redshifts. For this analysis, we use the photometric classification framework SuperNNova (SNN; Möller et al. 2019) trained on realistic DES-like simulations. For reliable classification, we process the DES SN programme (DES-SN) data and introduce improvements to the classifier architecture, obtaining classification accuracies of more than 98 per cent on simulations. This is the first SN classification to make use of ensemble methods, resulting in more robust samples. Using photometry, host galaxy redshifts, and a classification probability requirement, we identify 1,863 SNe Ia from which we select 1,484 cosmology-grade SNe Ia spanning the redshift range of 0.07 < z < 1.14. We find good agreement between the light-curve properties of the photometrically-selected sample and simulations. Additionally, we create similar SN Ia samples using two types of Bayesian Neural Network classifiers that provide uncertainties on the classification probabilities. We test the feasibility of using these uncertainties as indicators for out-of-distribution candidates and model confidence. Finally, we discuss the implications of photometric samples and classification methods for future surveys such as Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST).

astro-ph.CO↗

arXiv2022

Exploring stellar and ionized gas non--circular motions in barred galaxies with MUSE

We present MUSE integral field stellar and ionized velocity maps for a sample of 14 barred galaxies. Most of these objects exhibit "S"-shape iso-velocities in the bar region indicative of the presence of streaming motions in the velocity fields. % By applying circular rotation models we observe that bars leave symmetric structures in the residual maps of the stellar velocity. %which demonstrates the capabilities of the MUSE instrument for detecting kinematic bar signatures. % We built non-circular rotation models using the \xs~tool to characterize the observed velocity fields. In particular we adopt bisymmetric models and a harmonic decomposition for a bar potential for describing the non-axisymmetric velocities. We find that both models reproduce the observed kinematic features. % The position angle of the oval distortion estimated from the bisymmetric model correlates with the photometric bar position angle $(ρ_{pearson} = 0.95)$, which suggest that non-circular velocities are caused by the bar. However because of the low amplitudes of the $s_3$ harmonic we can not rule out radial flows as possible source. % Because of the weak detection of \ha~in our objects we are not able to compare gas to stellar non-circular motions in our sample, although we show that when galaxies are gas rich the oval distortion is also observed but with larger amplitudes. % Finally, we do not find evidence that the amplitude of the non-circular motions is dependent on the bar size, stellar mass or the global SFR.

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arXiv2022

Examining the Properties of Low-Luminosity Hosts of Type Ia Supernovae from ASAS-SN

We present a spectroscopic analysis of 44 low-luminosity host galaxies of Type Ia supernovae (SNe Ia) detected by the All-Sky Automated Survey for Supernovae (ASAS-SN), using the emission lines to measure metallicities and star formation rates. We find that although the star formation activity of our sample is representative of general galaxies, there is some evidence that the lowest-mass SN Ia host galaxies (log($M_\star/M_\odot$)$<8$) in our sample have high metallicities compared to general galaxies of similar masses. We also identify a subset of 5 galaxies with particularly high metallicities. This highlights the need for spectroscopic analysis of more low-luminosity, low-mass SN Ia host galaxies to test the robustness of these conclusions and their potential impact on our understanding of SN Ia progenitors.

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arXiv2022

A galaxy-driven model of type Ia supernova luminosity variations

Type Ia supernovae (SNe Ia) are used as standardisable candles to measure cosmological distances, but differences remain in their corrected luminosities which display a magnitude step as a function of host galaxy properties such as stellar mass and rest-frame $U-R$ colour. Identifying the cause of these steps is key to cosmological analyses and provides insight into SN physics. Here we investigate the effects of SN progenitor ages on their light curve properties using a galaxy-based forward model that we compare to the Dark Energy Survey 5-year SN Ia sample. We trace SN Ia progenitors through time and draw their light-curve width parameters from a bimodal distribution according to their age. We find that an intrinsic luminosity difference between SNe of different ages cannot explain the observed trend between step size and SN colour. The data split by stellar mass are better reproduced by following recent work implementing a step in total-to-selective dust extinction ratio $(R_V)$ between low- and high-mass hosts, although an additional intrinsic luminosity step is still required to explain the data split by host galaxy $U-R$. Modelling the $R_V$ step as a function of galaxy age provides a better match overall. Additional age vs. luminosity steps marginally improve the match to the data, although most of the step is absorbed by the width vs. luminosity coefficient $α$. Furthermore, we find no evidence that $α$ varies with SN age.

astro-ph.GA↗

arXiv2022

Testing the Homogeneity of Type Ia Supernovae in the Near-Infrared for Accurate Distance Estimations

Type Ia Supernovae (SNe Ia) have been extensively used as standardisable candles in the optical for several decades. 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 peak magnitudes in $J$ ($J_{max}$) and $H$ ($H_{max}$) bands. The use of a single NIR epoch only introduces an additional scatter of $\sim0.05$ mag for epochs around the time of $B$-band peak magnitude ($T_{max}$). We also tested the effect of optical cadence and signal-to-noise ratio (S/N) in the estimation of $T_{max}$ and its uncertainty propagation to the NIR peak magnitudes. Both cadence and S/N have a similar contribution, where we constrained the introduced scatter of each to $<0.02$ mag in $J_{max}$ and $<0.01$ in $H_{max}$. However, these effects are expected to be negligible, provided the data quality is comparable to that obtained for observations of nearby SNe ($z\lesssim0.1$). The effect of S/N in the NIR was tested as well. For SNe Ia at $0.08<z\lesssim0.1$, NIR observations with better S/N than that found in the CSP sample is necessary to constrain the introduced scatter to a minimum ($\lesssim0.05$ mag). 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, parameterised by $fD$, and the Hubble-Lemaître constant, $H_0$.

astro-ph.CO↗

arXiv2022

SN 2018bsz: a Type I superluminous supernova with aspherical circumstellar material

We present a spectroscopic analysis of Type I superluminous supernova (SLSN-I), SN 2018bsz. While it closely resembles SLSNe-I, the multi-component H$α$ line appearing at $\sim30$ d post-maximum is the most atypical. The H$α$ is characterised by two emission components, one at $+3000$ km/s and a second at $-7500$ km/s, with a third, near-zero velocity component appearing after a delay. The blue and central components can be described by Gaussian profiles of intermediate width, but the red component is significantly broader and Lorentzian. The blue component evolves towards lower velocity before fading at $100$ d post-peak, concurrently with a light curve break. Multi-component profiles are observed in other hydrogen lines including Pa$β$, and in lines of Ca II and He I. Spectropolarimetry obtained before (10.2 d) and after (38.4 d) the appearance of the H lines show a large shift on the Stokes $Q$ -- $U$ plane consistent with SN 2018bsz undergoing radical changes in its geometry. Assuming the SN is almost unpolarised at 10.2 d, the continuum polarisation at 38.4 d reaches $P \sim1.8\%$ implying a highly asymmetric configuration. We propose that the observed evolution of SN 2018bsz can be explained by highly aspherical CSM. After the SN explosion, the CSM is quickly overtaken by the ejecta, but as the photosphere starts to recede, the different CSM regions re-emerge producing the peculiar line profiles. Based on the first appearance of H$α$, we can constrain the distance of the CSM to be less than $430$ AU, or even lower ($<87$ AU) if the pre-peak plateau is related to an eruption that created the CSM. The presence of CSM has been inferred for other SLSNe-I. However, it is not clear whether the rare properties of SN 2018bsz can be generalised for SLSNe-I or whether they are the result of an uncommon evolutionary path, possibly involving a binary companion.

astro-ph.HE↗

arXiv2022

Evaluating and Optimizing a Slitless Prism for Nancy Grace Roman Space Telescope SN Cosmology

This work presents a set of studies addressing the use of the low-dispersion slitless prism on Roman for SN spectroscopy as part of the Roman High Latitude Time Domain Survey (HLTDS). We find SN spectral energy distributions including prism data carry more information than imaging alone at fixed total observing time, improving redshift measurements and sub-typing of SNe. The Roman field of view will typically include ~ 10 SNe Ia at observable redshifts at a range of phases (the multiplexing of host galaxies is much greater as they are always present), building up SN spectral time series without targeted observations. We show that fitting these time series extracts more information than stacking the data over all the phases, resulting in a large improvement in precision for SN Ia subclassification measurements. A prism on Roman thus significantly enhances scientific opportunities for the mission, and is particularly important for the Roman SN cosmology program to provide the systematics-controlled measurement that is a focus of the Roman dark energy mission. Optimizing the prism parameters, we conclude that the blue cutoff should be set as blue as the prism image quality allows (~ 7500A), the red cutoff should be set to ~ 18000A to minimize thermal background, and the two-pixel dispersion should be >~ 70.

astro-ph.CO↗

arXiv2022

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

The most stringent local measurement of the Hubble-Lemaître constant from Cepheid-calibrated Type Ia supernovae (SNe~Ia) differs from the value inferred via the cosmic microwave background radiation ({\it Planck}$+Λ$CDM) by $\sim 5σ$. 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-Lemaître constant. From 13 SNe~II with geometric, Cepheid, or tip of the red giant branch (TRGB) host-galaxy distance measurements, we derive H$_0= 75.4^{+3.8}_{-3.7}$\,km\,s$^{-1}$\,Mpc$^{-1}$ (statistical errors only), consistent with the local measurement but in disagreement by $\sim 2.0σ$ with the {\it Planck}$+Λ$CDM value. Using only Cepheids ($N=7$), we find H$_0 = 77.6^{+5.2}_{-4.8}$\,km\,s$^{-1}$\,Mpc$^{-1}$, while using only TRGB ($N=5$), we derive H$_0 = 73.1^{+5.7}_{-5.3}$\,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 statistically significant difference between the Cepheid and TRGB H$_0$ measurements -- our work reveals no indication that SNe~Ia or Cepheids could be the sources of the "H$_0$ tension." We caution, however, that our conclusions rest upon a modest calibrator sample; as this sample grows in the future, our results should be verified.

astro-ph.CO↗

arXiv2022

A Speed Bump: SN 2021aefx Shows that Doppler Shift Alone can Explain Early-Excess Blue Flux in Some Type Ia Supernovae

We present early-time photometric and spectroscopic observations of the Type Ia Supernova (SN Ia) 2021aefx. The early time u-band light curve shows an excess flux when compared to normal SNe Ia. We suggest that the early-excess blue flux may be due to a rapid change in spectral velocity in the first few days post explosion, produced by the emission of the Ca II H&K feature passing from the u to the B bands on the time scale of a few days. This effect could be dominant for all SNe Ia which have broad absorption features and early-time velocities over 25,000 km/s. It is likely to be one of the main causes of early-excess u-band flux in SNe Ia which have early-time high-velocities. This effect may also be dominant in the UV filters, as well as in places where the SN spectral energy distribution is quickly rising to longer wavelengths. The rapid change in velocity can only produce a monotonic change (in flux-space) in the u-band. For objects which explode at lower velocities, and have a more structured shape in the early-excess emission, there must also be an additional parameter producing the early-time diversity. More early time observations, in particular early spectra, are required to determine how prominent this effect is within SNe Ia.

astro-ph.HE↗

arXiv2022

Progenitor, environment, and modelling of the interacting transient, AT 2016jbu (Gaia16cfr)

We present the bolometric lightcurve, identification and analysis of the progenitor candidate, and preliminary modelling of AT2016jbu (Gaia16cfr). We find a progenitor consistent with a $\sim$22--25~$M_{\odot}$ yellow hypergiant surrounded by a dusty circumstellar shell, in agreement with what has been previously reported. We see evidence for significant photometric variability in the progenitor, as well as strong H$α$ emission consistent with pre-existing circumstellar material. The age of the environment as well as the resolved stellar population surrounding AT2016jbu, support a progenitor age of $>$10 Myr, consistent with a progenitor mass of $\sim$22~$M_{\odot}$. A joint analysis of the velocity evolution of AT2016jbu, and the photospheric radius inferred from the bolometric lightcurve shows the transient is consistent with two successive outbursts/explosions. The first outburst ejected material with velocity $\sim$650$kms^{-1}$, while the second, more energetic event, ejected material at $\sim$4500$kms^{-1}$. Whether the latter is the core-collapse of the progenitor remains uncertain. We place a limit on the ejected $^{56}$Ni mass of $<$0.016$M_{\odot}$. Using the BPASS code, we explore a wide range of possible progenitor systems, and find that the majority of these are in binaries, some of which are undergoing mass transfer or common envelope evolution immediately prior to explosion. Finally, we use the SNEC code to demonstrate that the low-energy explosion within some of these binary systems, together with sufficient CSM, can reproduce the overall morphology of the lightcurve of AT2016jbu.

astro-ph.HE↗

arXiv2022

Photometric and spectroscopic evolution of the interacting transient AT 2016jbu (Gaia16cfr)

We present the results from a high cadence, multi-wavelength observation campaign of AT 2016jbu (aka Gaia16cfr), an interacting transient. This dataset complements the current literature by adding higher cadence as well as extended coverage of the lightcurve evolution and late-time spectroscopic evolution. Photometric coverage reveals that AT 2016jbu underwent significant photometric variability followed by two luminous events, the latter of which reached an absolute magnitude of M$_V\sim$-18.5 mag. This is similar to the transient SN 2009ip whose nature is still debated. Spectra are dominated by narrow emission lines and show a blue continuum during the peak of the second event. AT 2016jbu shows signatures of a complex, non-homogeneous circumstellar material (CSM). We see slowly evolving asymmetric hydrogen line profiles, with velocities of 500km$s^{-1}$ seen in narrow emission features from a slow moving CSM, and up to 10,000km$s^{-1}$ seen in broad absorption from some high velocity material. Late-time spectra ($\sim$+1 year) show a lack of forbidden emission lines expected from a core-collapse supernova and are dominated by strong emission from H, He i and Ca ii. Strong asymmetric emission features, a bumpy lightcurve, and continually evolving spectra suggest an inhibit nebular phase. We compare the evolution of H$α$ among SN 2009ip-like transients and find possible evidence for orientation angle effects. The light-curve evolution of AT 2016jbu suggests similar, but not identical, circumstellar environments to other SN 2009ip-like transients.

astro-ph.SR↗

arXiv2022

pyHIIextractor: A tool to detect and extract physical properties of HII regions from Integral Field Spectroscopic data

We present a new code named pyHIIextractor, which detects and extracts the main features (positions and radii) of clumpy ionized regions, i.e. candidate HII regions, using Hα emission line images. Our code is optimized to be used on the dataproducts provided by the Pipe3D pipeline (or dataproducts with such a format), applied to high spatial resolution Integral Field Spectroscopy data (like that provided by the AMUSING++ compilation, using MUSE). The code provides the properties of both the underlying stellar population and the emission lines for each detected H ii candidate. Furthermore, the code delivers a novel estimation of the diffuse ionized gas (DIG) component, independent of its physical properties, which enables a decontamination of the properties of the HII regions from the DIG. Using simulated data, mimicking the expected observations of spiral galaxies, we characterise pyHIIextractor and its ability to extract the main properties of the H ii regions (and the DIG), including the line fluxes, ratios and equivalent widths. Finally, we compare our code with other such tools adopted in the literature, which have been developed or used for similar purposes: pyhIIexplorer, SourceExtractor, HIIphot, and astrodendro. We conclude that pyHIIextractor exceeds the performance of previous tools in aspects such as the number of recovered regions and the distribution of sizes and fluxes (an improvement that is especially noticeable for the faintest and smallest regions). pyHIIextractor is therefore an optimals tool to detect candidate HII regions, offering an accurate estimation of their properties and a good decontamination of the DIG component.

astro-ph.GA↗

arXiv2022

A detailed spectroscopic study of Tidal Disruption Events

Spectroscopically, TDEs are characterized by broad ( 10$^{4}$ km/s) emission lines and show large diversity as well as different line profiles. After carefully and consistently performing a series of data reduction tasks including host galaxy light subtraction, we present here the first detailed, spectroscopic population study of 16 optical/UV TDEs. We report a time lag between the peaks of the optical light-curves and the peak luminosity of H$α$ spanning between 7 - 45 days. If interpreted as light-echoes, these lags correspond to distances of 2 - 12 x 10$^{16}$ cm, one to two orders of magnitudes larger than the estimated blackbody radii (R$_{\rm BB}$) of the same TDEs and we discuss the possible origin of this surprisingly large discrepancy. We also report time lags for the peak luminosity of He I $λ$5876 line; smaller than the ones of H$α$ for H TDEs and similar or larger for N III Bowen TDEs. We report that N III Bowen TDEs have lower H$α$ velocity widths compared to the rest of the TDEs in our sample and we also find that a strong X-ray to optical ratio might imply weakening of the line widths. Furthermore, we study the evolution of line luminosities and ratios with respect to their radii (R$_{\rm BB}$) and temperatures (T$_{\rm BB}$). We find a linear relationship between H$α$ luminosity and the R$_{\rm BB}$ and potentially an inverse power-law relation with T$_{\rm BB}$ leading to weaker H$α$ emission for T$_{\rm BB}$ $\geq$ 25000 K. The He II/He I ratio becomes large at the same temperatures possibly pointing to an ionization effect. The He II/H$α$ ratio becomes larger as the photospheric radius recedes, implying a stratified photosphere where Helium lies deeper than Hydrogen. We suggest that the large diversity of the spectroscopic features seen in TDEs along with their X-ray properties, can potentially be attributed to viewing angle effects.

astro-ph.HE↗

arXiv2022

Low luminosity Type II supernovae -- IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class

Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) are presented. SN 2020cxd reaches a peak absolute magnitude $M_{r}$ = -13.90 $\pm$ 0.05 mag two days after explosion, subsequently settling on a plateau for $\sim$120 days. Through the luminosity of the late light curve tail, we infer a synthesized $^{56}$Ni mass of (1.8$\pm$0.5) $\times$ 10$^{-3}$ M$_{\odot}$. During the early evolutionary phases, optical spectra show a blue continuum ($T$ $>$ 8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases Ca II, Fe II, Sc II and Ba II lines dominate the spectra. Hydrodynamical modelling of the observables yields $R$ $\simeq$ 575 $R_{\odot}$ for the progenitor star, with $M_{ej}$ = 7.5 M$_{\odot}$ and $E$ $\simeq$ 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asymptotic giant branch star. SN 2021aai reaches a maximum luminosity of $M_{r}$ = -16.4 mag (correcting for $A_{V}$=1.9 mag), and displays a remarkably long plateau ($\sim$140 days). The estimated $^{56}$Ni mass is (1.4$\pm$0.5) $\times$ 10$^{-2}$ M$_{\odot}$. The expansion velocities are compatible with those of other LL SNe IIP (few 10$^{3}$ km s$^{-1}$). The physical parameters obtained through hydrodynamical modelling are $R$ $\simeq$ 575 R$_{\odot}$, $M_{ej}$ = 15.5 M$_{\odot}$ and $E$ = 0.4 foe. SN 2021aai is therefore interpreted as the explosion of a RSG, with properties that bridge the class of LL SNe IIP with standard SN IIP events.

astro-ph.SR↗

arXiv2022

Type II supernovae from the Carnegie Supernova Project-I. III. Understanding SN II diversity through correlations between physical and observed properties

SNe II show great photometric and spectroscopic diversity which is attributed to the varied physical characteristics of their progenitor and explosion properties. In this study, the third of a series of papers where we analyse a sample of SNe II observed by the Carnegie Supernova Project-I, we present correlations between their observed and physical properties. Our analysis shows that explosion energy is the physical property that correlates with the highest number of parameters. We recover previously suggested relationships between the hydrogen-rich envelope mass and the plateau duration, and find that more luminous SNe II with higher expansion velocities, faster declining light curves, and higher Ni masses are consistent with higher energy explosions. In addition, faster declining SNe II are also compatible with more concentrated Ni in the inner regions of the ejecta. Positive trends are found between the initial mass, explosion energy, and Ni mass. While the explosion energy spans the full range explored with our models, the initial mass generally arises from a relatively narrow range. Observable properties were measured from our grid of models to determine the effect of each physical parameter on the observed SN II diversity. We argue that explosion energy is the physical parameter causing the greatest impact on SN II diversity, when assuming standard single-star evolution as in the models used in this study. The inclusion of pre-SN models assuming higher mass loss produces a significant increase in the strength of some correlations, particularly those between the progenitor hydrogen-rich envelope mass and the plateau and optically thick phase durations. These differences clearly show the impact of having different treatments of stellar evolution, implying that changes in the assumption of standard single-star evolution are necessary for a complete understanding of SN II diversity.

astro-ph.SR↗

arXiv2022

Measuring Cosmological Parameters with Type Ia Supernovae in redMaGiC galaxies

Current and future cosmological analyses with Type Ia Supernovae (SNe Ia) face three critical challenges: i) measuring redshifts from the supernova or its host galaxy; ii) classifying SNe without spectra; and iii) accounting for correlations between the properties of SNe Ia and their host galaxies. We present here a novel approach that addresses each challenge. In the context of the Dark Energy Survey (DES), we analyze a SNIa sample with host galaxies in the redMaGiC galaxy catalog, a selection of Luminous Red Galaxies. Photo-$z$ estimates for these galaxies are expected to be accurate to $σ_{Δz/(1+z)}\sim0.02$. The DES-5YR photometrically classified SNIa sample contains approximately 1600 SNe and 125 of these SNe are in redMaGiC galaxies. We demonstrate that redMaGiC galaxies almost exclusively host SNe Ia, reducing concerns with classification uncertainties. With this subsample, we find similar Hubble scatter (to within $\sim0.01$ mag) using photometric redshifts in place of spectroscopic redshifts. With detailed simulations, we show the bias due to using photo-$z$s from redMaGiC host galaxies on the measurement of the dark energy equation-of-state $w$ is up to $Δw \sim 0.01-0.02$. With real data, we measure a difference in $w$ when using redMaGiC photometric redshifts versus spectroscopic redshifts of $Δw = 0.005$. Finally, we discuss how SNe in redMaGiC galaxies appear to be a more standardizable population due to a weaker relation between color and luminosity ($β$) compared to the DES-3YR population by $\sim5σ$; this finding is consistent with predictions that redMaGiC galaxies exhibit lower reddening ratios ($\textrm{R}_\textrm{V}$) than the general population of SN host galaxies. These results establish the feasibility of performing redMaGiC SN cosmology with photometric survey data in the absence of spectroscopic data.

astro-ph.CO↗

arXiv2022

HII regions in CALIFA survey: II. The relation between their physical properties and galaxy evolution

We present in here the exploration of the physical properties of the sample of HII regions and aggregations of the last HII regions catalog of the CALIFA survey. This sample comprises the optical spectroscopic properties of more than ~26,000 ionized regions corresponding to 924 galaxies from the Integral Field Spectroscopy data, including the flux intensity and equivalent widths and the properties of their underlying stellar population. In the current study we derive a set of physical quantities for all these regions based on those properties, including (i) the fraction of young stars; (ii) the ionization strength (using six different estimations); (iii) the oxygen abundance (using 25 different calibrators); (iv) the nitrogen and nitrogen-to-oxygen abundance; (v) the dust extinction and (vi) the electron density. Using this dataset we explore how the loci in the classical diagnostic diagrams are connected with those quantities, the radial distributions of these parameters, and the inter-relations between themselves and with the properties of the underlying stellar populations. We conclude that many properties of the HII regions are tightly related to the galactic stellar evolution at the location where those regions are observed. Those properties are modulated only as a second-order effect by the properties of the ionizing stars and the ionized nebulae that do not depend on the astrophysical context in which they are formed. Our results highlight the importance of HII regions to explore the chemical evolution in galaxies, clarifying which of their properties can be used as proxies of that evolution.

astro-ph.GA↗