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ÈThe size and luminosity vs. p correlations in NGC 4449, from the Ha data. The correlation between log R and log p (left), and log p log R F , (center) and log L and log p (right) for the regions of highest surface brightness, with symmetric spectral proÐles and good S/N, measured in Ha.
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Here we present the size and luminosity versus velocity dispersion empirical correlations for the giant H II regions in the large irregular galaxy NGC 4449. We show that correlations only hold for nebulae with a surface brightness higher than 2 × 1035 ergs s-1 pc-2 in Hα and with a supersonic single-line Gaussian profile. The exponents of the fits...
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... resulting set of points has been Ðtted using a stan- dard regression procedure, accounting for the errors in abscissas and ordinates associated to every single point. Figure 4 shows the correlations between log R, and log R F , log L versus log p obtained from the Ha line proÐles. And Figure 5 shows the correlations obtained using the [O III] data. ...
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... While comparing the results from the previous "L-σ" relation, differences in central values of the best-fit cosmological parameters were also reported: W = -+ 0.22 m 0.04 0.06 . The possible cosmological application of these HIIGx and GEHRs as standard candles has been extensively discussed in the literature (Fuentes-Masip et al. 2000;Bosch et al. 2002;Telles 2003;Siegel et al. 2005;Bordalo & Telles 2011;Plionis et al. 2011;Chávez et al. 2012Chávez et al. , 2014Mania & Ratra 2012;Wei et al. 2016). It was found that the H II galaxies provide a competitive source of luminosity distance to probe the acceleration of the universe. ...
Cosmological applications of H ii galaxies and giant extragalactic H ii regions (GEHRs) to construct the Hubble diagram at high redshifts require knowledge of the “ L – σ ” relation of the standard candles used. In this paper, we study the properties of a large sample of 156 sources (25 high- z H ii galaxies, 107 local H ii galaxies, and 24 GEHRs) compiled by Terlevich et al. Using the cosmological distances reconstructed through two new cosmology-independent methods, we investigate the correlation between the H β emission-line luminosity L and the ionized gas velocity dispersion σ . The method is based on non-parametric reconstruction using the measurements of Hubble parameters from cosmic clocks, as well as the simulated data of gravitational waves from the third-generation gravitational wave detector (the Einstein Telescope, ET), which can be considered as standard sirens. Assuming the relation between emission-line luminosity and ionized gas velocity dispersion, , we find that the full sample provides a tight constraint on the correlation parameters. However, similar analysis done on three different subsamples seems to support the scheme of treating H ii galaxies and GEHRs with distinct strategies. Using the corrected “ L – σ ” relation for the H ii observational sample beyond the current reach of Type Ia supernovae, we obtain values of the matter density parameter, Ω m = 0.314 ± 0.054 (calibrated with standard clocks) and Ω m = 0.311 ± 0.049 (calibrated with standard sirens), in the spatially flat ΛCDM cosmology.
... The scatter in the L(Hβ) − σ relation is small enough that it can be used to determine cosmic distances independently of redshift (see Melnick et al. 1988Melnick et al. , 2000Fuentes-Masip et al. 2000;Bosch et al. 2002;Siegel et al. 2005;Bordalo & Telles 2011;Chávez et al. 2012Chávez et al. , 2014Fernández Arenas et al. 2018). ...
Massive starforming regions like Giant H II Regions (GHIIR) and H II Galaxies (HIIG) are emission line systems ionized by compact young massive star clusters (YMC) with masses ranging from 104M⊙ to 108M⊙. 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 (MB − σ) 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 σ vs. MB plane coincides – depending on the initial mass – either with the globular clusters for systems with initial mass M < 106M⊙ or with a continuation of the ellipticals, bulges of spirals and ultracompact dwarfs for YMC with M > 106M⊙. The slope change in the MB − σ and MB-size relations at cluster masses around 106M⊙ 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.
... The scatter in the L(Hβ) − σ relation is small enough that it can be used to determine cosmic distances independently of redshift (see Melnick et al. 1988Melnick et al. , 2000Fuentes-Masip et al. 2000;Bosch et al. 2002;Siegel et al. 2005;Bordalo & Telles 2011;Chávez et al. 2012Chávez et al. , 2014Fernández Arenas et al. 2018). ...
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.
... It has been noted that the luminosity L(Hβ) in Hβ in these systems is strongly correlated with the ionized gas velocity dispersion σ [4], presumably because both the number of ionizing photons and the turbulent velocity of the gas increase with the mass in the starburst component [6,7]. This strong correlation and a relatively small dispersion in the relationship between L(Hβ) and σ makes it possible to consider and use these galaxies (and HII regions) as standard candles [1,[6][7][8][9][10][11][12][13][14][15][16][17]. ...
The Hubble diagram constructed using HII galaxies (HIIGx) and Giant extragalactic HII regions (GEHR) as standard candles already extends beyond the current reach of Type Ia SNe. A sample of 156 HIIGx and GEHR sources has been used previously to compare the predictions of LCDM and R_h=ct, the results of which suggested that the HIIGx and GEHR sources strongly favour the latter over the former. But this analysis was based on the application of parametric fits to the data and the use of information criteria, which disfavour the less parsimonious models. In this paper, we advance the use of HII sources as standard candles by utilizing Gaussian processes (GP) to reconstruct the distance modulus representing these data without the need to pre-assume any particular model, none of which may in the end actually be the correct cosmology. In addition, this approach tightly constrains the 1 sigma confidence region of the reconstructed function, thus providing a better tool with which to differentiate between competing cosmologies. With this approach, we show that the Planck concordance model is in tension with the HII data at more than 2.5 sigma, while R_h=ct agrees with the GP reconstruction very well, particularly at redshifts > 10^{-3}.
We consider several well-known f(R) cosmological models and constrain their parameters, namely the deviation parameter b and the cosmological parameters Ωm and h. We first obtain analytical approximations for the Hubble rate H(z) and the luminosity distance dL(z) in terms of these parameters, and then test these against the observational expansion rate derived from cosmic chronometers and the distance modulus in the H ii galaxy Hubble diagram, obtained in a model-independent way using Gaussian Processes (GP). We first optimize the models based solely on the cosmic chronometers and then repeat this process with a joint analysis using both the cosmic chronometers and H ii galaxies.
Since Sep. 2018, LAMOST has started the medium-resolution ( R ∼ 7500) spectral survey (MRS). We proposed the spectral survey of Galactic nebulae, including H ii regions, HH objects, supernova remnants, planetary nebulae and the special stars with MRS (LAMOST MRS-N). LAMOST MRS-N covers about 1700 square degrees of the northern Galactic plane within 40° < l < 215° and –5° < b < 5°. In this 5-year survey, we plan to observe about 500 thousand nebulae spectra. According to the commissioning observations, the nebulae spectra can provide precise radial velocity with uncertainty less than 1 km s ⁻¹ . These high-precision spectral data are of great significance to our understanding of star formation and evolution.
The cosmic distance duality relation (CDDR), η(z) = (1 + z)2dA(z)/dL(z) = 1, is one of the most fundamental and crucial formulae in cosmology. This relation couples the luminosity and angular diameter distances, two of the most often used measures of structure in the Universe. We here propose a new model-independent method to test this relation, using strong gravitational lensing (SGL) and the high-redshift quasar Hubble diagram reconstructed with a Bézier parametric fit. We carry out this test without pre-assuming a zero spatial curvature, adopting instead the value ΩK = 0.001 ± 0.002 optimized by Planck in order to improve the reliability of our result. We parametrize the CDDR using η(z) = 1 + η0z, 1 + η1z + η2z2 and 1 + η3z/(1 + z), and consider both the SIS and non-SIS lens models for the strong lensing. Our best fit results are: $\eta _0=-0.021^{+0.068}_{-0.048}$, $\eta _1=-0.404^{+0.123}_{-0.090}$, $\eta _2=0.106^{+0.028}_{-0.034}$, and $\eta _3=-0.507^{+0.193}_{-0.133}$ for the SIS model, and $\eta _0=-0.109^{+0.044}_{-0.031}$ for the non-SIS model. The measured η(z), based on the Planck parameter ΩK, is essentially consistent with the value (=1) expected if the CDDR were fully respected. For the sake of comparison, we also carry out the test for other values of ΩK, but find that deviations of spatial flatness beyond the Planck optimization are in even greater tension with the CDDR. Future measurements of SGL may improve the statistics and alter this result but, as of now, we conclude that the CDDR favours a flat Universe.
The cosmic distance duality (CDD) relation (based on the Etherington reciprocity theorem) plays a crucial role in awide 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 aGaussian 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 Rh = ct universe and ΛCDM - and show that Rh = ct is favoured by the CDD data with a likelihood ~82.3 per cent compared with ~17.7 per cent for the standard model.
Using a representative sample of 14 star-forming dwarf galaxies in the local Universe, we show the existence of a spaxel-to-spaxel anti-correlation between the index N2 (log([NII]6583/Halpha)) and the Halpha flux. These two quantities are commonly employed as proxies for gas-phase metallicity and star formation rate (SFR), respectively. Thus, the observed N2 to Halpha relation may reflect the existence of an anti-correlation between the metallicity of the gas forming stars and the SFR it induces. Such an anti-correlation is to be expected if variable external metal-poor gas fuels the star-formation process. Alternatively, it can result from the contamination of the star-forming gas by stellar winds and SNe, provided that intense outflows drive most of the metals out of the star-forming regions. We also explore the possibility that the observed anti-correlation is due to variations in the physical conditions of the emitting gas, other than metallicity. Using alternative methods to compute metallicity, as well as previous observations of HII regions and photoionization models, we conclude that this possibility is unlikely. The radial gradient of metallicity characterizing disk galaxies does not produce the correlation either.
