HII Galaxies Research Articles

HII galaxies as standard candles: Evolutionary corrections

Over the past decade, the relation between the Balmer-line luminosity of HII galaxies and the velocity width of the emission lines, the relation, has been painstakingly calibrated as a cosmological distance indicator with seemingly spectacular results: the Hubble constant and the energy density of dark energy obtained using the indicator agree remarkably well with the values from canonical indicators. Since most of the luminosity of these young compact starburst galaxies is emitted by a few narrow emission lines, they can be observed with good precision up to redshifts of $z with JWST, making the indicator a potentially unique cosmological probe. However, the precision of the method remains too low to effectively constrain the relevant cosmological parameters, notably the equation of state of dark energy. The scatter of the relation is significantly larger than the random observational errors, so we do not have a good handle on the systematics of the method. In a previous paper, we posited that since the ionizing radiation of these young galaxies fades rapidly over timescales of only a few million years, age differences could be the main underlying cause of the scatter. In this paper, we explore several different ways of explaining the scatter of the correlation, but without success. We show that the majority of HII galaxies are powered by multiple starbursts of slightly different ages, and therefore that the equivalent widths are not reliable chronometers to correct the luminosities for evolution. Thus, it is not likely that the accuracy of the distance indicator can be improved in the near future. Since we do not fully understand either the systematics or the underlying physics of the relation, using large samples of distant HII galaxies may or may not improve the accuracy of the method.

ΛCDM-Rastall cosmology revisited: constraints from a recent Quasars datasample

In this paper we study the impact of a recent quasar datasample in the constraint of the free parameters of an extension of general relativity. As a ruler to test, we use Rastall gravity in the context of background cosmology being a simple extension to general relativity. We compare the results from quasars dataset with other known samples such as cosmic chronometers, supernovae of the Ia type, baryon acoustic oscillations, HII galaxies, and also a joint analysis. Results are consistent with the standard cosmological model emphasizing that Rastall gravity is equivalent to general relativity. According to the constraints provided from the joint sample, the age of the Universe is τU=12.601−0.066+0.067 Gyrs and the transition to an accelerated phase occurs at zT=0.620±0.025 in the redshift scale, being only the phase transition consistent with the standard paradigm and having a younger Universe. With the quasars sample, the Universe age differs with that expected in ΛCDM having a result of τU=11.958−0.109+0.139 Gyrs with a transition at zT=0.652±0.032 this last consistent with standard cosmology. A remarkable result is that quasars constraints has the capability to differentiate among general relativity and Rastall gravity due to the result for the parameter λ=−2.231−0.546+0.785 . Moreover, the parameter j under quasars constraints suggests that the cause of the late Universe’s acceleration is a dark energy fluid different from a cosmological constant.

Simultaneous measurements on cosmic curvature and opacity using latest HII regions and H(z) observations

The different spatial curvatures of the universe affect the measurement of cosmological distances, which may also contribute to explaining the observed dimming of type Ia supernovae. This phenomenon may be caused by the opacity of the universe. Similarly, the opacity of the universe can lead to a bias in our measurements of curvature. Thus, it is necessary to measure cosmic curvature and opacity simultaneously. In this paper, we propose a new model-independent method to simultaneously measure the cosmic curvature and opacity by using the latest observations of HII galaxies acting as standard candles and the latest Hubble parameter observations. The machine learning method-Artificial Neural Network is adopted to reconstruct observed Hubble parameter H(z) observations. Our results support a slightly opaque and flat universe at 1sigma confidence level by using previous 156 HII regions sample. However, the negative curvature is obtained by using the latest 181 HII regions sample in the redshift range zsim 2.5. More importantly, we obtain the simultaneous measurements with precision on the cosmic opacity mathrm Delta tau sim 10^{-2} and curvature mathrm Delta Omega _Ksim 10^{-1}. A strong degeneracy between the cosmic opacity and curvature parameters is also revealed in this analysis.

A Reliable Calibration of H ii Galaxies Hubble Diagram with Cosmic Chronometers and Artificial Neural Network

The L–σ relation of H ii galaxies (HIIGx) calibrated by a distance indicator is a reliable standard candle for measuring the Hubble constant H 0. The most straightforward calibration technique anchors them with the first tier of distance ladders from the same galaxies. Recently another promising method that uses the cosmological model–independent cosmic chronometers as a calibrator has been proposed. We promote this technique by removing the assumptions about the cosmic flatness and using a nonparametric artificial neural network for the data reconstruction process. We observe a correlation between the cosmic curvature density parameter and the slope of the L–σ relation, thereby improving the reliability of the calibration. Using the calibrated HIIGx Hubble diagram, we obtain a Type Ia supernovae Hubble diagram free of the conventional assumption about H 0. Finally we get a value of , which is compatible with the latest Planck 18 measurement.

The VANDELS survey: Global properties of CIII]λ1908 Å emitting star-forming galaxies at z ∼ 3

Context. Strong nebular emission is ubiquitous in galaxies that contribute to cosmic reionization at redshift z ≳ 6. High-ionization UV metal lines, such as CIII]λ1908 Å, show high equivalent widths (EW) in these early galaxies, suggesting harder radiation fields at low metallicity than low-z galaxies of similar stellar mass. Understanding the physical properties driving the observed UV nebular line emission at high-z requires large and very deep spectroscopic surveys, which are now only accessible out to z ∼ 4. Aims. We study the mean properties of a large representative sample of 217 galaxies showing CIII] emission at 2 < z < 4, selected from a parent sample of ∼750 main-sequence star-forming galaxies in the VANDELS survey. These CIII] emitters have a broad range of UV luminosities, allowing for a detailed stacking analysis to characterize their stellar mass, star formation rate (SFR), and metallicity as a function of the UV emission line ratios, EWs, and the carbon-to-oxygen (C/O) abundance ratio. Methods. Stacking provides unprecedented high signal-to-noise (S/N) spectra for CIII] emitters over more than three decades in luminosity, stellar mass, and SFR. This enables a full spectral fitting to derive stellar metallicities for each stack. Moreover, we use diagnostics based on photoionization models and UV line ratios to constrain the ionization sources of the galaxies and derive the C/O abundance. Results. Reliable CIII] detections (S/N ≥ 3) represent ∼30% of the parent sample. However, stacked spectra of non-detections (S/N < 3) show weak (EW ≲ 2 Å) CIII] emission, suggesting that this line is common in normal star-forming galaxies at z ∼ 3. On the other hand, extreme CIII] emitters (EW(CIII]) ≳ 8 Å) are exceedingly rare (∼3%) in VANDELS. The UV line ratios of the sample suggest no ionization source other than massive stars. Stacks with larger EW(CIII]) show larger EW(Lyα) and lower metallicity, but not all CIII] emitters are Lyα emitters. The stellar metallicities of CIII] emitters are not significantly different from that of the parent sample, increasing from ∼10% to ∼40% solar for stellar masses log(M⋆/M⊙) ∼ 9−10.5. The stellar mass-metallicity relation of the CIII] emitters is consistent with previous works, exhibiting a strong evolution from z = 0 to z ∼ 3. The C/O abundances of the sample range between 35%−150% solar, with a noticeable increase with FUV luminosity and a smooth decrease with the CIII] EW. Here, we discuss the CIII] emitters in the C/O–Fe/H and the C/O–O/H planes and we find that they follow stellar and nebular abundance trends consistent with those of Milky Way halo and thick-disk stars and local HII galaxies, respectively. A qualitative agreement is also found with chemical evolution models, which suggests that CIII] emitters at z ∼ 3 are experiencing an active phase of chemical enrichment. Conclusions. Our results provide new insights into the nature of UV line emitters at z ∼ 2 − 4, paving the way for future studies at higher z using the James Webb Space Telescope.

Observational constraints and predictions of the interacting dark sector with field-fluid mapping

We consider an interacting field theory model that describes the interaction between dark energy-dark matter interaction. Only for a specific interaction term, this interacting field theory description has an equivalent interacting fluid description. For inverse power law potentials and linear interaction function, we show that the interacting dark sector model with field-fluid mapping is consistent with four cosmological data sets — Hubble parameter measurements (Hz), Baryonic Acoustic Oscillation data (BAO), Supernova Type Ia data (SN), and High redshift HII galaxy measurements (HIIG). More specifically, these data sets prefer a negative value of interaction strength in the dark sector and lead to consistent best-fit values of Hubble constant and other cosmological parameters. Having established that this interacting field theory model is consistent with cosmological observations, we obtain quantifying tools to distinguish between the interacting and non-interacting dark sector scenarios. We focus on the variation of the scalar metric perturbed quantities as a function of redshift related to structure formation, weak gravitational lensing, and the integrated Sachs-Wolfe effect. We show that the difference in the evolution becomes significant for z < 20, for all length scales, and the difference peaks at smaller redshift values z < 5. We then discuss the implications of our results for the upcoming missions.

Barrow Entropy Cosmology: an observational approach with a hint of stability analysis

In this work, we use an observational approach and dynamical system analysis to study the cosmological model recently proposed by Saridakis (2020), which is based on the modification of the entropy-area black hole relation proposed by Barrow (2020). The Friedmann equations governing the dynamics of the Universe under this entropy modification can be calculated through the gravity-thermodynamics conjecture. We investigate two models, one considering only a matter component and the other including matter and radiation, which have new terms compared to the standard model sourcing the late cosmic acceleration. A Bayesian analysis is performed in which using five cosmological observations (observational Hubble data, type Ia supernovae, HII galaxies, strong lensing systems, and baryon acoustic oscillations) to constrain the free parameters of both models. From a joint analysis, we obtain constraints that are consistent with the standard cosmological paradigm within 2σ confidence level. In addition, a complementary dynamical system analysis using local and global variables is developed which allows obtaining a qualitative description of the cosmology. As expected, we found that the dynamical equations have a de Sitter solution at late times.

Using our newest VLT-KMOS HII galaxies and other cosmic tracers to test the Lambda cold dark matter tension

ABSTRACT We place novel constraints on the cosmokinetic parameters by using a joint analysis of the newest Very Large Telescope (VLT)-K-band Multi Object Spectrograph (KMOS) HII galaxies (HIIG) with the Type Ia Supernovae (SNIa) Pantheon sample. We combine the latter data sets in order to reconstruct, in a model-independent way, the Hubble diagram to as high redshifts as possible. Using a Gaussian process, we derive the basic cosmokinetic parameters and compare them with those of Lambda cold dark matter (ΛCDM). In the case of SNIa, we find that the extracted values of the cosmokinetic parameters are in agreement with the predictions of ΛCDM model. Combining SNIa with high-redshift tracers of the Hubble relation, namely HIIG data, we obtain consistent results with those based on ΛCDM as far as the present values of the cosmokinetic parameters are concerned, but find significant deviations in the evolution of the cosmokinetic parameters with respect to the expectations of the concordance ΛCDM model.

Revisiting the cosmic distance duality relation with machine learning reconstruction methods: the combination of HII galaxies and ultra-compact radio quasars

In this paper, we carry out an assessment of cosmic distance duality relation (CDDR) based on the latest observations of HII galaxies acting as standard candles and ultra-compact structure in radio quasars acting as standard rulers. Particularly, two machine learning reconstruction methods [Gaussian Process (GP) and Artificial Neural Network (ANN)] are applied to reconstruct the Hubble diagrams from observational data. We show that both approaches are capable of reconstructing the current constraints on possible deviations from the CDDR in the redshift range zsim 2.3. Considering four different parametric methods of CDDR, which quantify deviations from the CDDR and the standard cosmological model, we compare the results of the two different machine learning approaches. It is observed that the validity of CDDR is in well agreement with the current observational data within 1sigma based on the reconstructed distances through GP in the overlapping redshift domain. Moreover, we find that ultra-compact radio quasars could provide 10^{-3}-level constraints on the violation parameter at high redshifts, when combined with the observations of HII galaxies. In the framework of ANN, one could derive robust constraints on the violation parameter at a precision of 10^{-2}, with the validity of such distance duality relation within 2sigma confidence level.

Cosmological constraints using the newest VLT-KMOS H ii galaxies and the full Planck CMB spectrum

ABSTRACT We present novel cosmological constraints based on a joint analysis of our H ii galaxies (HIIG) Hubble relation with the full Planck cosmic microwave background (CMB) anisotropy spectrum and the baryon acoustic oscillations (BAO) probes. The HIIG span a large redshift range (0.088 ≤ z ≤ 2.5), reaching significantly higher redshifts than available Type Ia supernovae (SNeIa) and hence they probe the cosmic expansion at earlier times. Our independent constraints compare well with those based on the ‘Pantheon’ compilation of SNeIa data, which we also analyse. We find our results to be in agreement with the conformal Λ cold dark matter (ΛCDM) model within 1σ. We also use our HIIG data to examine the behaviour of the dark energy equation-of-state parameter under the Chevallier–Polarski–Linder (CPL) parametrization, w = w0 + waz/(1 + z), and find consistent results with those based on SNeIa, although the degeneracy in the parameter space and the individual parameter uncertainties, when marginalizing one over the other, are quite large.

Independent cosmological constraints from high-z H ii galaxies: new results from VLT-KMOS data

ABSTRACT We present independent determinations of cosmological parameters using the distance estimator based on the established correlation between the Balmer line luminosity, L(H β), and the velocity dispersion (σ) for H ii galaxies (HIIG). These results are based on new VLT-KMOS high spectral resolution observations of 41 high-z (1.3 ≤ z ≤2.6) HIIG combined with published data for 45 high-z and 107 z ≤0.15 HIIG, while the cosmological analysis is based on the MultiNest Markov Chain Monte Carlo (MCMC) procedure not considering systematic uncertainties. Using only HIIG to constrain the matter density parameter (Ωm), we find $\Omega _\mathrm{ m} = 0.244^{+0.040}_{-0.049}$ (stat), an improvement over our best previous cosmological parameter constraints, as indicated by a 37 per cent increase of the figure of merit. The marginalized best-fitting parameter values for the plane {Ωm; w0} = $\lbrace 0.249^{+0.11}_{-0.065}; -1.18^{+0.45}_{-0.41}\rbrace$ (stat) show an improvement of the cosmological parameters constraints by 40 per cent. Combining the HIIG Hubble diagram, the cosmic microwave background (CMB) and the baryon acoustic oscillation (BAO) probes yields Ωm = 0.298 ± 0.012 and w0 = −1.005 ± 0.051, which are certainly compatible – although less constraining – than the solution based on the joint analysis of Ia supernovae (SNIa), CMB and BAO measurements. An attempt to constrain the evolution of the dark energy with time (CPL model), using a joint analysis of the HIIG, CMB, and BAO measurements, shows a degenerate 1σ contour of the parameters in the {w0, wa} plane.

A hybrid model of viscous and Chaplygin gas to tackle the Universe acceleration

Motivated by two seminal models proposed to explain the Universe acceleration, this paper is devoted to study a hybrid model which is constructed through a generalized Chaplygin gas with the addition of a bulk viscosity. We call the model a viscous generalized Chaplygin gas (VGCG) and its free parameters are constrained through several cosmological data like the Observational Hubble Parameter, Type Ia Supernovae, Baryon Acoustic Oscillations, Strong Lensing Systems, HII Galaxies and using Joint Bayesian analysis. In addition, we implement a Om-diagnostic to analyze the VGCC dynamics and its difference with the standard cosmological model. The hybrid model shows important differences when compared with the standard cosmological model. Finally, based on our Joint analysis we find that the VGCG could be an interesting candidate to alleviate the well-known Hubble constant tension.

Einstein–Gauss–Bonnet gravity: Is it compatible with modern cosmology?

Einstein–Gauss–Bonnet (EGB) model is recently restudied in order to analyze new consequences in gravitation, modifying appropriately the Einstein–Hilbert action. The consequences in EGB cosmology are mainly geometric, with higher order values in the Hubble parameter. In this vein this paper is devoted to contribute with extra evidences about its pros and cons of the model from a cosmological point of view. We start constraining the characteristic parameter, α , of the EGB model when a cosmological constant as the catalyst for the acceleration is considered. The constrictions are developed at the background cosmology using Observational Hubble Data, Baryon Acoustic Oscillations, Supernovas of the Ia type, Strong Lensing Systems and the recent compilation of HII Galaxies. Additionally, we implement a statefinder analysis where we found not only a late acceleration but also an early Universe acceleration which is associated with the parameter α . Based on our results of the lensing systems, the Universe evolution never reaches a non accelerated phase, instead it is always presented in an accelerated state, being a possible fault that afflicts the EGB model.

Star formation and AGN activities in selected nearby HII galaxies in the LeMMINGS survey

AbstractWe investigate the relative fraction of the emission generated by star formation and nuclear activities in 6 nearby HII galaxies selected from the first high resolution radio data release of LeMMINGS, the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies Survey. These galaxies are supposed to be powered solely by star formation according to the BPT diagram but exhibit jetted morphologies on parsec scales indicating the presence of a low luminosity AGN. We further carried out a multi-wavelength SED fiiting and analysis using the CIGALE code, estimating stellar masses and star formation rates.

The varying cosmological constant models tested with Supernovae Type Ia and HII Galaxy Data

Abstract We have recently proposed a varying cosmological constant model for which we now test our proposal with the use of two large collections of observational Gold data of supernovae Type Ia (SNe Ia) and HII Galaxies (HIIGx) data as standard candles for constructing the Hubble diagram at redshifts beyond the current reach of Type Ia supernovae. For this aim, we obtain the luminosity distances from the proposed varying Λ models which have been briefly summarized. Using these luminosity distance values, we present the modulus values from which we test the accuracy of the models by probing the Gold data and HII Data confirming that the relation between the emission-line luminosity and ionized-gas velocity dispersion is a reliable modulus indicator. From the χ 2 minimization and the maximization of the likelihood function, we optimize the cosmological parameters in each cosmological model. While the best model is obtained as the Λ CDM for Gold data, our model with a Λ depending on the matter density ρ is obtained as the best model for HII data. Moreover, the statistical tools, such as the Akaike (AIC), and Bayes (BIC) Information Criteria favor the standard Λ CDM model over our Λ ∝ ρ model with a relative BIC of 372/383 for Gold data, but same criteria favor our Λ ∝ ρ model over Λ CDM with 1055/1120 for HII Galaxy data. We also test the accuracy of our models by comparison of the theoretical and observational modulus values for both data, and illustrate the Hubble diagrams for all varying Λ models showing a worse fit with respect to Λ CDM model for Gold Data, and a best fit with Λ ∝ ρ model for HII Data, through given statistical confidence tables.

Independent cosmological constraints from high-z H ii galaxies

We present new high spectral resolution observations of 15 high-z ($1.3 \leq$ z $\leq 2.5$) HII Galaxies (HIIG) obtained with MOSFIRE at the Keck Observatory. These data, combined with already published data for another 31 high-z and 107 z $\leq 0.15$ HIIG, are used to obtain new independent cosmological results using the distance estimator based on the established correlation between the Balmer emission line velocity dispersion and luminosity for HIIG. Our results are in excellent agreement with the latest cosmological concordance model ($\Lambda$CDM) published results. From our analysis, we find a value for the mass density parameter of $\Omega_m=0.290^{+0.056}_{-0.069}$ (stat). For a flat Universe we constrain the plane $\lbrace\Omega_m;w_0\rbrace = \lbrace 0.280^{+0.130}_{-0.100} ; -1.12^{+0.58}_{-0.32}\rbrace $ (stat). The joint likelihood analysis of HIIG with other complementary cosmic probes (Cosmic Microwave Background and Baryon Acoustic Oscillations) provides tighter constraints for the parameter space of the Equation of State of Dark Energy that are also in excellent agreement with those of similar analyses using Type Ia Supernovae instead as the geometrical probe.

Searching for the evidence of dynamical dark energy

In the statistical framework of model-independent Gaussian processes (GP), we search for the evidence of dynamical dark energy (DDE) using the “Joint Light-curve Analysis” (JLA) Type Ia supernovae (SNe Ia) sample, the 30 latest cosmic chronometer data points (H(z)), Planck’s shift parameter from cosmic microwave background (CMB) anisotropies, the 156 latest HII galaxy measurements and 79 calibrated gamma-ray bursts (GRBs). We find that the joint constraint from JLA + H(z) + CMB + HII + GRB supports the global measurement of H_0 by Planck collaboration very much in the low redshift range zin [0, 0.76] at the 2sigma confidence level (C.L.), gives a cosmological constant crossing (quintom-like) equation of state (EoS) of DE at the 2sigma C.L. and implies that the evolution of the late-time Universe may be actually dominated by the DDE.

A comparison of the Rh = ct and ΛCDM cosmologies using the cosmic distance duality relation

The cosmic distance duality (CDD) relation (based on the Etherington reciprocity theorem) plays a crucial role in a wide assortment of cosmological measurements. Attempts at confirming it observationally have met with mixed results, though the general consensus appears to be that the data do support its existence in nature. A common limitation with past approaches has been their reliance on a specific cosmological model, or on measurements of the luminosity distance to Type Ia SNe, which introduces a dependence on the presumed cosmology in spite of beliefs to the contrary. Confirming that the CDD is actually realized in nature is crucial because its violation would require exotic new physics. In this paper, we study the CDD using the observed angular size of compact quasar cores and a Gaussian Process reconstruction of the HII galaxy Hubble diagram---without pre-assuming any particular background cosmology. In so doing, we confirm at a very high level of confidence that the angular-diameter and luminosity distances do indeed satisfy the CDD. We then demonstrate the potential power of this result by utilizing it in a comparative test of two competing cosmological models---the R_h=ct universe and LCDM---and show that R_h=ct is favoured by the CDD data with a likelihood ~82.3% compared with ~17.7% for the standard model.

From Giant H ii regions and H ii galaxies to globular clusters and compact dwarf ellipticals

Massive starforming regions like Giant HII Regions (GHIIR) and HII Galaxies (HIIG) are emission line systems ionized by compact young massive star clusters (YMC) with masses ranging from $10^4$M$_\odot$ to $10^8$M$_\odot$. We model the photometric and dynamical evolution over a Hubble time of the massive gravitationally bound systems that populate the tight relation between absolute blue magnitude and velocity dispersion ($M_{B}-\sigma$) of GHIIR and HIIG and compare the resulting relation with that one of old stellar systems: globular clusters, elliptical galaxies, bulges of spirals. After 12~Gyr of evolution their position on the $\sigma$ vs. M$_B$ plane coincides -- depending on the initial mass -- either with the globular clusters for systems with initial mass $M < 10^6$M$_\odot$ or with a continuation of the ellipticals, bulges of spirals and ultracompact dwarfs for YMC with $M >10^6$M$_\odot$. The slope change in the $M_{B}-\sigma$ and $M_B$-size relations at cluster masses around $10^6$M$_\odot$ is due to the larger impact of the dynamical evolution on the lower mass clusters. We interpret our result as an indication that the YMC that ionize GHIIR and HIIG can evolve to form globular clusters and ultra compact dwarf ellipticals in about 12 Gyr so that present day globular clusters and ultra compact dwarf ellipticals may have formed in conditions similar to those observed in today GHIIR and HIIG.

Stellar populations of HII galaxies

Aims. We present a UV to mid-IR spectral energy distribution (SED) study of a large sample of SDSS DR13 HII galaxies. These galaxies are selected as starbursts (EW(Hα) &gt; 50Å) and for their high-excitation locus in the upper left region of the BPT diagram. Their photometry was derived from the cross-matched GALEX, SDSS, UKDISS, and WISE catalogs. Methods. We used CIGALE modeling and a SED fitting routine with the parametrization of a three-burst star formation history, and a comprehensive analysis of all other model parameters. We were able to estimate the contribution of the underlying old stellar population to the observed equivalent width of Hβ, and allow for more accurate burst age determination. Results. We found that the star formation histories of HII Galaxies can be reproduced remarkably well by three major eras of star formation. In addition, the SED fitting results indicate that in all cases the current burst produces a small percent of the total stellar mass, i.e., the bulk of stellar mass in HII galaxies has been produced by the past episodes of star formation, and also indicate that at a given age the Hβ luminosity depends only on the mass of young stars favoring a universal IMF for massive stars. Most importantly, the current star formation episodes are maximum starbursts that produce stars at the highest possible rate.