Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

This paper uses the first XMM–Newton Serendipitous Source Catalog compiled by the XMM–Newton Science Centre to identify low-z X-ray selected normal galaxy candidates. Our sample covers a total area of ≈6 deg² to the 0.5–2 keV limit ≈10⁻¹⁵ erg s⁻¹ cm⁻². A total of 23 sources are selected on the basis of low X-ray to optical flux ratio log f_X/f_opt < −2, soft X-ray spectral properties and optical spectra, when available, consistent with stellar formation rather than active galactic nucleus (AGN) processes. This sample is combined with similarly selected systems from the Needles in the Haystack Survey to provide a total of 46 unique (z≲ 0.2) X-ray detected normal galaxies, the largest low-z sample yet available. This is first used to constrain the normal galaxy log N–log S at bright fluxes (10⁻¹⁵–10⁻¹³ erg s⁻¹ cm⁻²). We estimate a slope of −1.46 ± 0.13 for the cumulative number counts consistent with the Euclidean prediction. We further combine our sample with 23 local (z≲ 0.2) galaxies from the Chandra Deep Field-North and -South surveys to construct the local X-ray luminosity function of normal galaxies. A Schechter form provides a good fit to the data with a break at log L_★= 41.02^+0.14_−0.12 erg s⁻¹ and a slope of α=−1.76 ± 0.10. Finally, for the sample of 46 systems, we explore the association between X-ray luminosity and host galaxy properties, such as star formation rate (SFR) and stellar mass. We find that the L_X of the emission-line systems correlates with Hα luminosity and 1.4-GHz radio power, both providing an estimate of the current SFR. In the case of early-type galaxies with absorption-line optical spectra, we use the K band as an approximation of stellar mass and find a correlation of the form L_X∝L^1.5_K. This is flatter than the L_X–L_B relation for local ellipticals. This may be due to either L_K providing a better approximation of galaxy mass or selection effects biasing our sample against very luminous early-type galaxies, L_X > 10⁴² erg s⁻¹.

We investigated the physical characteristics of the broad line region (BLR) of NGC 5548 using the Boltzmann plot (BP) method, which we applied to the Balmer lines observed from 1996 to 2004. We found that variability earlier detected in the lines is also present in the temperature parameter $A$, obtained from the BP method. Using the BP temperature parameter $A$ to calculate temperature, we found that the average temperature for the considered period was $T \approx$10000 K, and that it varies from 5000K (in 2002) to 15000K (in 1998). This variation correlates with the AGN-component of the optical continuum flux ($r=$ 0.85), and may indicate the existence of an accretion disk in the BLR of NGC 5548.

A noise suppression approach was developed and applied for pitting corrosion studies of chromatized 6061-T6 airspace aluminum alloy by Scanning Vibrating Electrode Technique (SVET). The proposed approach is based on the power line frequency application as a SVET probe driving frequency combined with a synchronized double integration of the SVET probe signal yielding a free of noise signal product. Noise suppression up to -58 dB was achieved allowing precise measurement of the ionic current above the corroded metal surface proving the opportunity to replace the high cost lock-in amplifier.

The foot is considered a wonder of biological engineering due to its structure, formed by bones, ligaments, and tendons that collaborate to ensure stability and mobility. A key area often examined by medical professionals in patients with diabetic feet is the plantar surface, due to the risk of ulcer development. If left untreated, these ulcers can lead to severe complications, including amputation of the toe, foot, or even the limb. Interpolation methods are used to find areas with overloads in a system of sensor maps that are based on capacitive, load cells, or force-sensitive resistors (FSRs). This manuscript presents the assessment of linear, nearest neighbors, and bicubic methods in comparison with ground truth to calculate the root mean square error (RMSE) in two assessments using a dataset of eight healthy subjects, four men and four women, with an average age of 25 years, height of 1.63 m, and weight of 72 kg with shoe sizes from 7.3 USA using FSR map with 48 sensors. Additionally, this paper describes the conditioning circuit development to implement a plantar surface system that enables interpolating loads on the plantar surface. The proposed system’s results show that the first assessment indicates an RMSE of 0.089, 0.126, and 0.089 for linear, nearest neighbor, and bicubic methods, while the second assessment shows a mean RMSE for linear, nearest neighbor, and bicubic methods of 0.114, 0.159, and 0.112.