The Fundamental Plane for early-type galaxies. Dependence on the magnitude range

Studying 3 samples of early-type galaxies, which include approximately 8800 galaxies and cover a relatively ample magnitude range ($$ $\sim 5$ $mag$), we find that the coefficients as well as the intrinsic dispersion of the Fundamental Plane depend on the width of the magnitude range within which the galaxies are distributed. We analyse this dependence and the results show that it could be due to the fact that the distribution of galaxies in the space defined by the variables $\log (r_{e}), _{e}, \log(\sigma)$ depends on the luminosity.Comment: 11 pages, 5 figures. MNRAS. Accepte

The Faber-Jackson relation for early-type galaxies: Dependence on the magnitude range

We take a sample of early-type galaxies from the Sloan Digital Sky Survey (SDSS-DR7, $\sim$ 90 000 galaxies) spanning a range of approximately 7 $mag$ in both $g$ and $r$ filters and analyse the behaviour of the Faber-Jackson relation parameters as functions of the magnitude range. We calculate the parameters in two ways: i) We consider the faintest (brightest) galaxies in each sample and we progressively increase the width of the magnitude interval by inclusion of the brighter (fainter) galaxies (increasing-magnitude-intervals), and ii) we consider narrow-magnitude intervals of the same width ($\Delta M = 1.0$ $mag$) over the whole magnitude range available (narrow-magnitude-intervals). Our main results are that: i) in both increasing and narrow-magnitude-intervals the Faber-Jackson relation parameters change systematically, ii) non-parametric tests show that the fluctuations in the values of the slope of the Faber-Jackson relation are not products of chance variations. We conclude that the values of the Faber-Jackson relation parameters depend on the width of the magnitude range and the luminosity of galaxies within the magnitude range. This dependence is caused, to a great extent by the selection effects and because the geometrical shape of the distribution of galaxies on the $M - \log (\sigma_{0})$ plane depends on luminosity. We therefore emphasize that if the luminosity of galaxies or the width of the magnitude range or both are not taken into consideration when comparing the structural relations of galaxy samples for different wavelengths, environments, redshifts and luminosities, any differences found may be misinterpreted.Comment: 15 pages, 5 figures. A&A. Accepte

CCD Photometry of the Globular Cluster NGC 5897

We report CCD photometric observations of the globular cluster NGC 5897, in the Johnson system filters B, V , R, and I. With the values for these magnitudes we obtain various colour indices and produce several colour-magnitude diagrams. We present eight colour-magnitude diagrams: V vs B-V , B vs B-V , V vs V-I, I vs V-I, R vs R-I, I vs R-I, V vs V-R, and R vs V-R. In all of these diagrams we can clearly see the Giant Branch, the Horizontal Branch and the beginning of the Main Sequence. To the left of the Main Sequence turn-off point we detect a somewhat large number of Blue Straggler stars. We determine the mean value of the visual magnitude of the HB as $16.60 \pm 0.46$. This value is fainter than the value found by other authors.Comment: 28 pages, 7 figures, accepted for publication RevMexAA, vol. 60-1, April 2024. arXiv admin note: text overlap with arXiv:1606.0452

Collision of molecular outflows in the L1448--C system

We present a study of the central zone of the star-forming region L1448 at 217--230 GHz ($\sim$ 1.3 mm) using ALMA observations. Our study focuses on the detection of proto-stellar molecular outflows and the interaction with the surrounding medium toward sources L1448--C(N) and L1448--C(S). Both sources exhibit continuum emission, with L1448--C(N) being the brightest one. Based on its spectral index and the associated bipolar outflow, the continuum emission is the most likely to be associated with a circumstellar disk. The $^{\rm 12}$CO(J=2$\rightarrow$1) and SiO(J= 5$\rightarrow$4) emissions associated with L1448--C(N) trace a bipolar outflow and a jet oriented along the northwest-southeast direction. The $^{\rm 12}$CO(J=2$\rightarrow$1) outflow for L1448--C(N) has a wide-open angle and a V-shape morphology. The SiO jet is highly collimated and has an axial extent comparable with the $^{\rm 12}$CO(J=2$\rightarrow$1) emission. There is not SiO(J= 5$\rightarrow$4) emission towards L1448--C(S), but there is $^{\rm 12}$CO(J=2$\rightarrow$1) emission. The observations revealed that the red-shifted lobes of the $^{\rm 12}$CO(J=2$\rightarrow$1) outflows of L1448--C(N) and L1448--C(S) are colliding. As a result of this interaction, the L1448-C(S) lobe seems to be truncated. The collision of the molecular outflows is also hinted by the SiO(J= 5$\rightarrow$4) emission, where the velocity dispersion increases significantly in the interaction zone. We also investigated whether it could be possible that this collision triggers the formation of new stars in the L1448--C system.Comment: 11 pages, 7 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) DOI: 10.1093/mnras/stad98

How much dark matter is there inside early-type galaxies?

We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte

The Fundamental Plane of Early-Type Galaxies as a Confounding Correlation

Early-type galaxies are characterized by many scaling relations. One of them, the so-called fundamental plane is a relatively tight correlation between three variables, and has resisted a clear physical understanding despite many years of intensive research. Here, we show that the correlation between the three variables of the fundamental plane can be the artifact of the effect of another parameter influencing all, so that the fundamental plane may be understood as a confounding correlation. Indeed, the complexity of the physics of galaxies and of their evolution suggests that the main confounding parameter must be related to the level of diversification reached by the galaxies. Consequently, many scaling relations for galaxies are probably evolutionary correlations