Paola Álvarez-Hurtado
Gather.town id
CSF01
Poster Title
Exploring the impact of the Star Formation in the Mass-Metallicity relation at global scales
Institution
Instituto de Astronomía, UNAM
Abstract (short summary)
We explore the Mass-Metallicity relation (MZR) for ~1000 nearby galaxies using integrated properties from the extended version of the CALIFA integral field spectroscopy data. We focused on exploring the best mathematical form that describes the observed MZR through different functional forms as well as different statistical environments. To test the goodness of the fit of the MZR, we identify the function that yields the smallest scatter in its residuals. We use this residual to explore possible secondary relations of the MZR with other observables (e.g., SFR, Gas mass, gas fraction, and morphology). Among other results, we note a significant lack of an anti-correlation between these residuals and the SFR, in contrast to previous studies. Our results suggest that the functional form and the presence of secondary relations may depend on statistical treatment.
Plain text (extended) Summary
First slide:
To date, there is controversy if there is a second parameter that heavily reduces the scatter of the mass-metallicity relation (or MZR). The usual issues related are the aperture bias or the calibrator used.
So, with our study, we would like to overcome those biases properly using spatially resolved data at 1Re. Furthermore, we want to explore through a comprehensive statistical analysis if another parameter heavily reduced the scatter of the MZ scaling relation.
We compiled almost a thousand galaxies from the extended CALIFA (here and after eCALIFA) sample. We include one of the most extensive CO-derived datasets available from the EDGE and APEX surveys.
This collection comprises almost 600 eCALIFA galaxies with data measurements of molecular gas. The datasets will allow us to study many physical properties of galaxies: structural, stellar, molecular properties, among others.
To start our journey, we selected low-tilt star-forming galaxies. We use the strong emission line method to determine the oxygen abundance based on the O3N2 calibrator. However, we performed the same analysis for six more calibrators of different nature.
Second slide:
According to the literature, the MZR shape is associated with different functional forms. So we apply an agnostic statistical treatment over different functional forms, binning schemes, and fit criteria. We found that the best shape corresponds to a 3rd degree polynomial. The solid red line in the upper-left figure represents our best fit in the oxygen abundance - stellar-mass plain and is fully consistent with previous analysis with other Integral Field Spectroscopy datasets.
With the best shape of the MZR, we avoid introducing any bias in metallicity residuals analysis, as the figure of the bottom shows. So the next question is, what drives metallicity? We analyzed the Pearson correlation factor between 23 parameters with the metallicity of the ionized gas. The right-hand figure shows the behavior of the correlation factor between metallicity and each of these parameters plotted in descending order. The blue points are associated with positive correlations. The red points are associated with negative correlations. We focus on those observables that return a correlation factor greater than 0.3 to reduce the space parameters.
Inside the grey region, we can find the parameters that significantly correlate with metallicity.
So, we want to explore if, after characterizing the MZR, these parameters continue affecting the scaling relation or not. In other words, if those parameters correlate with the residuals of the MZR.
Third slide:
We emphasize the usual suspects: the total star-formation rate, Gas fraction, and molecular gas mass.
In the last figure, we present the oxygen abundance residuals distributions against those suspect parameters. In each panel, the distribution of our eCALIFA star-forming galaxies sample is represented by grey density contours, encircling 50, 80, and 90 percent. The green and grey lines trace the eCALIFA and EDGE-APEX distributions, respectively, through a linear fit between the residuals and the observable. We statistically quantified any trend computed correlation factor, scatter reduction, and slopes between residuals against each observable.
According to our analysis, all the distributions are relatively flat, with no significant trends, correlations, nor scatter reduction for any observable explored. We find similar results with the other six calibrations analyzed. This last implies that there is no evidence of secondary dependency with MZR, exploring 23 observables, even with the star-formation rate, gas fraction or molecular gas mass.
To date, there is controversy if there is a second parameter that heavily reduces the scatter of the mass-metallicity relation (or MZR). The usual issues related are the aperture bias or the calibrator used.
So, with our study, we would like to overcome those biases properly using spatially resolved data at 1Re. Furthermore, we want to explore through a comprehensive statistical analysis if another parameter heavily reduced the scatter of the MZ scaling relation.
We compiled almost a thousand galaxies from the extended CALIFA (here and after eCALIFA) sample. We include one of the most extensive CO-derived datasets available from the EDGE and APEX surveys.
This collection comprises almost 600 eCALIFA galaxies with data measurements of molecular gas. The datasets will allow us to study many physical properties of galaxies: structural, stellar, molecular properties, among others.
To start our journey, we selected low-tilt star-forming galaxies. We use the strong emission line method to determine the oxygen abundance based on the O3N2 calibrator. However, we performed the same analysis for six more calibrators of different nature.
Second slide:
According to the literature, the MZR shape is associated with different functional forms. So we apply an agnostic statistical treatment over different functional forms, binning schemes, and fit criteria. We found that the best shape corresponds to a 3rd degree polynomial. The solid red line in the upper-left figure represents our best fit in the oxygen abundance - stellar-mass plain and is fully consistent with previous analysis with other Integral Field Spectroscopy datasets.
With the best shape of the MZR, we avoid introducing any bias in metallicity residuals analysis, as the figure of the bottom shows. So the next question is, what drives metallicity? We analyzed the Pearson correlation factor between 23 parameters with the metallicity of the ionized gas. The right-hand figure shows the behavior of the correlation factor between metallicity and each of these parameters plotted in descending order. The blue points are associated with positive correlations. The red points are associated with negative correlations. We focus on those observables that return a correlation factor greater than 0.3 to reduce the space parameters.
Inside the grey region, we can find the parameters that significantly correlate with metallicity.
So, we want to explore if, after characterizing the MZR, these parameters continue affecting the scaling relation or not. In other words, if those parameters correlate with the residuals of the MZR.
Third slide:
We emphasize the usual suspects: the total star-formation rate, Gas fraction, and molecular gas mass.
In the last figure, we present the oxygen abundance residuals distributions against those suspect parameters. In each panel, the distribution of our eCALIFA star-forming galaxies sample is represented by grey density contours, encircling 50, 80, and 90 percent. The green and grey lines trace the eCALIFA and EDGE-APEX distributions, respectively, through a linear fit between the residuals and the observable. We statistically quantified any trend computed correlation factor, scatter reduction, and slopes between residuals against each observable.
According to our analysis, all the distributions are relatively flat, with no significant trends, correlations, nor scatter reduction for any observable explored. We find similar results with the other six calibrations analyzed. This last implies that there is no evidence of secondary dependency with MZR, exploring 23 observables, even with the star-formation rate, gas fraction or molecular gas mass.
URL
palvarez@astro.unam.mx
Poster file