The progenitors of superluminous supernovae (SLSNe) are still a mystery. Hydrogen-poor SLSN hosts are young, highly star-forming dwarf galaxies and the majority belongs to the class of ‘extreme ...emission line galaxies’. Here we present a resolved long-slit study of the host of the hydrogen-poor SLSN PTF12dam probing the kiloparsec environment of the SN site to determine the age of the progenitor. The SN occurred in a star-forming region in the head of a ‘tadpole’ galaxy with largely uniform properties. The galaxy experienced a recent starburst superimposed on an underlying old stellar population (SP). We determine a very young SP at the SN site of ∼3 Myr and a metallicity of 12+log(O/H)=8.0 but do not observe any Wolf–Rayet features. The progenitor of PTF12dam was likely a massive star of >60 M⊙ and one of the first stars exploding as an SN in the most recent starburst episode.
Aims.
Star-forming galaxies with nebular He
II
emission contain very energetic ionizing sources of radiation, which can be considered as analogs to the major contributors of the reionization of the ...Universe in early epochs. It is therefore of great importance to provide a reliable absolute scale for the equivalent effective temperature (
T
*
) for these sources.
Methods.
We study a sample of local (
z
< 0.2) star-forming galaxies showing optical nebular He
II
emission using the so-called softness diagrams, involving emission lines of two elements in two consecutive stages of ionization (e.g., S
II
/S
III
vs. O
II
/O
III
). We use for the first time the He
I
/He
II
ratio in these diagrams in order to explore the higher range of
T
*
expected in these objects, and to investigate the role of possible mechanisms driving the distribution of galaxy points in these diagrams. We build grids of photoionization models covering different black-body temperatures, model cluster atmospheres, and density-bounded geometries to explain the conditions observed in the sample.
Results.
We verified that the use of the softness diagrams including the emission-line ratio He
I
/He
II
combined with black-body photoionization models can provide an absolute scale of
T
*
for these objects. The application of a Bayesian-like code indicates
T
*
in the range 50−80 kK for the sample of galaxies, with a mean value higher than 60 kK. The average of these high temperature values can only be reproduced using cluster model populations with nearly metal-free stars, although such ionizing sources cannot explain either the highest
T
*
values, beyond 1
σ
, or the dispersion observed in the softness diagrams. According to our photoionization models, most sample galaxies could be affected to some extent by ionizing photon leaking, presenting a mean photon absorption fraction of 26% or higher depending on the metallicity assumed for the ionizing cluster. The entire range of He
I
/He
II
, S
II
/S
III
, and O
II
/O
III
ratios for these HeII-emitting galaxies is reproduced with our models, combining nearly metal-free ionizing clusters and photon leaking under different density-bounded conditions.
This paper describes the Second Public Data Release (DR2) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. The data for 200 objects are made public, including the 100 galaxies of the ...First Public Data Release (DR1). Data were obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto observatory. Two different spectral setups are available for each galaxy, (i) a low-resolution V500 setup covering the wavelength range 3745-7500 Angstrom with a spectral resolution of 6.0 Angstrom (FWHM); and (ii) a medium-resolution V1200 setup covering the wavelength range 3650-4840 Angstrom with a spectral resolution of 2.3 Angstrom (FWHM). The sample covers a redshift range between 0.005 and 0.03, with a wide range of properties in the color-magnitude diagram, stellar mass, ionization conditions, and morphological types. All the cubes in the data release were reduced with the latest pipeline, which includes improvedspectrophotometric calibration, spatial registration, and spatial resolution. The spectrophotometric calibration is better than 6% and the median spatial resolution is 2."4. In total, the second data release contains over 1.5 million spectra.
Bar pattern speeds in CALIFA galaxies Aguerri, J A L; Mendez-Abreu, J; Falcon-Barroso, J ...
Astronomy and astrophysics (Berlin),
4/2015, Letnik:
576
Journal Article
Recenzirano
Odprti dostop
The bar pattern speed (Omegab) is defined as the rotational frequency of the bar, and it determines the bar dynamics. Several methods have been proposed for measuring Omegab. This method has been ...applied so far to 17 galaxies, most of them SB0 and SBa types. We have applied the TW method to a new sample of 15 strong and bright barred galaxies, spanning a wide range of morphological types from SB0 to SBbc. Combining our analysis with previous studies, we investigate 32 barred galaxies with their pattern speed measured by the TW method. We measured Omegab using the TW method on the stellar velocity maps provided by the integral-field spectroscopy data from the CALIFA survey. Our results indicate that independent of the Hubble type, bars have been formed and then evolve as fast rotators. This observational result will constrain the scenarios of formation and evolution of bars proposed by numerical simulations.
Context. The study of the integrated properties of star-forming galaxies is central to understand their formation and evolution. Some of these properties are extensive and therefore their analysis ...require totally covering and spatially resolved observations. Among these properties, metallicity can be defined in spiral discs by means of integral field spectroscopy (IFS) of individual H ii regions. The simultaneous analysis of the abundances of primary elements, as oxygen, and secondary, as nitrogen, also provides clues about the star formation history and the processes that shape the build-up of spiral discs. Aims. Our main aim is to analyse simultaneously O/H and N/O abundance ratios in H ii regions in different radial positions of the discs in a large sample of spiral galaxies to obtain the slopes and the characteristic abundance ratios that can be related to their integrated properties. Methods. We analysed the optical spectra of individual selected H ii regions extracted from a sample of 350 spiral galaxies of the CALIFA survey. We calculated total O/H abundances and, for the first time, N/O ratios using the semi-empirical routine Hii-Chi-mistry, which, according to Pérez-Montero (2014, MNRAS, 441, 2663), is consistent with the direct method and reduces the uncertainty in the O/H derivation using N ii lines owing to the dispersion in the O/H-N/O relation. Then we performed linear fittings to the abundances as a function of the de-projected galactocentric distances. Results. The analysis of the radial distribution both for O/H and N/O in the non-interacting galaxies reveals that both average slopes are negative, but a non-negligible fraction of objects have a flat or even a positive gradient (at least 10% for O/H and 4% for N/O). The slopes normalised to the effective radius appear to have a slight dependence on the total stellar mass and the morphological type, as late low-mass objects tend to have flatter slopes. No clear relation is found, however, to explain the presence of inverted gradients in this sample, and there is no dependence between the average slopes and the presence of a bar. The relation between the resulting O/H and N/O linear fittings at the effective radius is much tighter (correlation coefficient ρs = 0.80) than between O/H and N/O slopes (ρs = 0.39) or for O/H and N/O in the individual H ii regions (ρs = 0.37). These O/H and N/O values at the effective radius also correlate very tightly (less than 0.03 dex of dispersion) with total luminosity and stellar mass. The relation with other integrated properties, such as star formation rate, colour, or morphology, can be understood only in light of the found relation with mass.
ABSTRACT
We apply fossil record techniques to the CALIFA sample to study how galaxies in the Local Universe have evolved in terms of their chemical content. We show how the stellar metallicity and ...the mass–metallicity relation (MZR) evolve through time for the galaxies in our sample and how this evolution varies when we divide them based on their mass, morphology, and star-forming status. We also check the impact of measuring the metallicity at the centre or the outskirts. We find the expected results that the most massive galaxies were enriched more quickly, and that the MZR was steeper at higher redshifts. However, once we separate the galaxies into morphology bins this behaviour is less clear, which suggests that morphology is a primary factor in determining how quickly a galaxy becomes enriched, but with mass determining the final enrichment. We also find that star-forming galaxies (SFGs) appear to be asymptotic in their chemical evolution; that is, the metallicity of SFGs of any mass is very similar at recent times unlike several Gyr ago.
ABSTRACT Variations in the stellar initial mass function (IMF) have been invoked to explain the spectroscopic and dynamical properties of early-type galaxies (ETGs). However, no observations have yet ...been able to disentangle the physical driver. We analyze here a sample of 24 ETGs drawn from the CALIFA survey, deriving in a homogeneous way their stellar population and kinematic properties. We find that the local IMF is tightly related to the local metallicity, becoming more bottom-heavy toward metal-rich populations. Our result, combined with the galaxy mass-metallicity relation, naturally explains previous claims of a galaxy mass-IMF relation, derived from non-IFU spectra. If we assume that-within the star formation environment of ETGs-metallicity is the main driver of IMF variations, a significant revision of the interpretation of galaxy evolution observables is necessary.
Abstract
We study a sample of 28 S0 galaxies extracted from the integral field spectroscopic (IFS) survey Calar Alto Legacy Integral Field Area. We combine an accurate two-dimensional (2D) ...multicomponent photometric decomposition with the IFS kinematic properties of their bulges to understand their formation scenario. Our final sample is representative of S0s with high stellar masses (M⋆/M⊙ > 1010). They lay mainly on the red sequence and live in relatively isolated environments similar to that of the field and loose groups. We use our 2D photometric decomposition to define the size and photometric properties of the bulges, as well as their location within the galaxies. We perform mock spectroscopic simulations mimicking our observed galaxies to quantify the impact of the underlying disc on our bulge kinematic measurements (λ and v/σ). We compare our bulge corrected kinematic measurements with the results from Schwarzschild dynamical modelling. The good agreement confirms the robustness of our results and allows us to use bulge deprojected values of λ and v/σ. We find that the photometric (n and B/T) and kinematic (v/σ and λ) properties of our field S0 bulges are not correlated. We demonstrate that this morpho-kinematic decoupling is intrinsic to the bulges and it is not due to projection effects. We conclude that photometric diagnostics to separate different types of bulges (disc-like versus classical) might not be useful for S0 galaxies. The morpho-kinematics properties of S0 bulges derived in this paper suggest that they are mainly formed by dissipational processes happening at high redshift, but dedicated high-resolution simulations are necessary to better identify their origin.
Resolving galaxies in time and space Fernandes, R Cid; Delgado, R M Gonzalez; Benito, R Garcia ...
Astronomy and astrophysics (Berlin),
1/2014, Letnik:
561
Journal Article
Recenzirano
In a companion paper we have presented many products derived from the application of the spectral synthesis code STARLIGHT to datacubes from the CALIFA survey, including 2D maps of stellar population ...properties and 1D averages in the temporal and spatial dimensions. Our goal here is to assess the uncertainties in these products. Uncertainties associated to noise and spectral shape calibration errors in the data and to the synthesis method were investigated by means of a suite of simulations, perturbing spectra and processing them through our analysis pipelines. The simulations used 1638 CALIFA spectra for NGC 2916, with perturbation amplitudes gauged in terms of the expected errors. Noise and shape-related errors at the level expected for C ALIFA propagate to uncertainties of 0.10-0.15 dex in stellar masses, mean ages, and metallicities. Spectral residuals are of the order of 1% on average, but with systematic features of up to 4% amplitude. We discuss the origin of these features, most of which are present in both in C ALIFA and SDSS spectra.
PDF
