arXiv subjects

Diego Ferreiro

Publications and source records attributed to Diego Ferreiro.

4 recordsLinked to original sources

arXiv2019

Characterization of the continuum and kinematical properties of nearby NLS1

In order to study the slope and strength of the non-stellar continuum, we analyzed a sample of nearby Narrow Line Seyfert 1 (NLS1). Also, we re-examined the location of NLS1 galaxies on the M $-$ $σ$ relation using the stellar velocity dispersion and the [OIII]$λ$5007 emission line as surrogate of the former. We studied spectra of a sample of 131 NLS1 galaxies taken from the Sloan Digital Sky Survey (SDSS) DR7. We approached determining the non-stellar continuum by employing the spectral synthesis technique, which uses the code {\sc starlight}, and by adopting a power-law base to model the non-stellar continuum. Composite spectra of NLS1 galaxies were also obtained based on the sample.In addition, we obtained the stellar velocity dispersion from the code and by measuring Calcium II Triplet absorption lines and [OIII] emission lines. From Gaussian decomposition of the H$β$ profile we calculated the black hole mass. We obtained a median slope of $β$ = $-$1.6 with a median fraction of contribution of the non-stellar continuum to the total flux of 0.64. We determined black hole masses in the range of log(M$_{BH}$/M$_{\odot}$) = 5.6 $-$ 7.5 which is in agreement with previous works. We found a correlation between the luminosity of the broad component of H$β$ and black hole mass with the fraction of a power-law component. Finally, according to our results, NLS1 galaxies in our sample are located mostly underneath the MBH - $σ_{\star}$ relation, both considering the stellar velocity dispersion ($σ_{\star}$) and the core component of [OIII]$λ$5007.

astro-ph.GA↗

arXiv2018

Asymmetric emission of the [OIII]$λ$5007 profile in narrow-line Seyfert 1 galaxies

Many active galactic nuclei (AGN) and particularly narrow-line Seyfert 1 (NLS1) galaxies, usually exhibit blueshifts and blue wings in several emission lines, which are mainly associated with outflows and strong winds. In order to study the radial velocity difference between the narrow component of H$β$ and the core component of [OIII]$λ$5007 and the asymmetric emission of this forbidden line, we investigate a sample of NLS1 galaxies . One of the aims of this paper is to analyze the blue wings of the [OIII]$λ$5007 profiles and their relation with the central engine. We have obtained and studied medium-resolution spectra (190 km s$^{-1}$ FWHM at H$β$) of a sample of 28 NLS1 galaxies in the optical range 4300 - 5200Å. We performed Gaussian decomposition to the H$β$ and [OIII]$λλ$4959,5007 emission profiles in order to study the distinct components of these lines. A new blue outlier galaxy is found, in which the center of the core component of [OIII] is blueshifted by 405 km s$^{-1}$ relative to the center of the narrow component of H$β$ line. We confirmed a previously known correlation between the blueshift and the full width half maximum (FWHM) of the core component of [OIII]$λ$5007 line. We also corroborated the correlation between the latter and the velocity of the centroid of the blue wing. On the other hand, by studying the radial velocity difference between the blue end of the asymmetric emission and the centroid of the core component of [OIII], we found a correlation between it and the central black hole mass and, therefore, with the luminosity of the broad component of H$β$. Finally, we found a moderate correlation between the luminosity of the [OIII] blue wing and the black hole mass.

astro-ph.GA↗

arXiv2016

Spectral nuclear properties of NLS1 galaxies

It is not yet well known whether narrow line Seyfert 1 (NLS1) galaxies follow the $M_{BH} - σ_{\star}$ relation found for normal galaxies. Emission lines, such as [SII] or [OIII]$λ$5007, have been used as a surrogate of the stellar velocity dispersion and various results have been obtained. On the other hand, some active galactic nuclei (AGNs) have shown Balmer emission with an additional intermediate component (IC) besides the well-known narrow and broad lines. In order to re-examine the location of NLS1 in the $M_{BH} - σ_{\star}$ relation, we test some emission lines, such as the narrow component (NC) of H$α$ and the forbidden [NII]$λλ$6548,6584 and [SII]$λλ$6716,6731 lines, as replacements for $σ_{\star}$. On the other hand, we study the properties of the IC of H$α$ found in 14 galaxies of the sample to find a link between this component, the central engine, and the remaining lines. We also compare the emission among the broad component (BC) of H$α$ and those emitted at the narrow line region (NLR). We have obtained and studied medium-resolution spectra (170 km s$^{-1}$ FWHM at H$α$) of 36 NLS1 galaxies in the optical range $\sim$5800 - 6800Å. We found that, in general, most of the galaxies lie below the $M_{BH} - σ_{\star}$ relation when the NC of H$α$, [SII], and [NII] lines are used as a surrogate of $σ_{\star}$. Besides this, we found that 13 galaxies show an IC, most of which are in the velocity range $\sim$ 700 $-$ 1500 km s$^{- 1}$. This is same range as in AGN types and is well correlated with the FWHM of BC and, therefore, with the BH mass. On the other hand, we found that there is a correlation between the luminosity of the BC of H$α$ and NC, IC, [NII]$λ$6584, and [SII] lines.

astro-ph.GA↗

arXiv2014

Capturing coevolutionary signals in repeat proteins

The analysis of correlations of amino acid occurrences in globular proteins has led to the development of statistical tools that can identify native contacts -- portions of the chains that come to close distance in folded structural ensembles. Here we introduce a statistical coupling analysis for repeat proteins -- natural systems for which the identification of domains remains challenging. We show that the inherent translational symmetry of repeat protein sequences introduces a strong bias in the pair correlations at precisely the length scale of the repeat-unit. Equalizing for this bias reveals true co-evolutionary signals from which local native-contacts can be identified. Importantly, parameter values obtained for all other interactions are not significantly affected by the equalization. We quantify the robustness of the procedure and assign confidence levels to the interactions, identifying the minimum number of sequences needed to extract evolutionary information in several repeat protein families. The overall procedure can be used to reconstruct the interactions at long distances, identifying the characteristics of the strongest couplings in each family, and can be applied to any system that appears translationally symmetric.

q-bio.BM↗