scholarly journals The stellar metallicity distribution function of galaxies in the CALIFA survey

2020 ◽  
Vol 499 (4) ◽  
pp. 4838-4853
Author(s):  
A Mejía-Narváez ◽  
S F Sánchez ◽  
E A D Lacerda ◽  
L Carigi ◽  
L Galbany ◽  
...  
Keyword(s):  
Distribution Function ◽  
Chemical Structure ◽  
Radial Distance ◽  
Clear Trend ◽  
Massive Galaxies ◽  
Chemical Enrichment ◽  
Integral Field Spectroscopy ◽  
Radial Profiles ◽  
Central Regions ◽  
Metallicity Distribution

ABSTRACT We present a novel method to retrieve the chemical structure of galaxies using integral field spectroscopy data through the stellar Metallicity Distribution Function (MDF). This is the probability distribution of observing stellar populations having a metallicity Z. We apply this method to a set of 550 galaxies from the CALIFA survey. We present the behaviour of the MDF as a function of the morphology, the stellar mass, and the radial distance. We use the stellar metallicity radial profiles retrieved as the first moment of the MDF, as an internal test for our method. The gradients in these radial profiles are consistent with the known trends: they are negative in massive early-type galaxies and tend to positive values in less massive late-type ones. We find that these radial profiles may not convey the complex chemical structure of some galaxy types. Overall, low mass galaxies (log M⋆/M⊙ ≤ 10) have broad MDFs ($\sigma _Z\sim 1.0\,$ dex), with unclear dependence on their morphology. However this result is likely affected by under-represented bins in our sample. On the other hand, massive galaxies (log M⋆/M⊙ ≥ 11) have systematically narrower MDFs ($\sigma _Z\le 0.2\,$ dex). We find a clear trend whereby the MDFs at rk/Re > 1.5 have large variance. This result is consistent with sparse SFHs in medium/low stellar density regions. We further find there are multimodal MDFs in the outskirts ($\sim 18\,$ per cent) and the central regions ($\sim 40\,$ per cent) of galaxies. This behaviour is linked to a fast chemical enrichment during early stages of the SFH, along with the posterior formation of a metal-poor stellar population.

scholarly journals SDSS IV MaNGA: Metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models

2020 ◽  
Vol 636 ◽  
pp. A42 ◽  
Author(s):  
M. Mingozzi ◽  
F. Belfiore ◽  
G. Cresci ◽  
K. Bundy ◽  
M. Bershady ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Theoretical Work ◽  
Universal Relation ◽  
Star Forming ◽  
Spatially Resolved ◽  
Integral Field Spectroscopy ◽  
Radial Profiles ◽  
Central Regions ◽  
Optical Line ◽  
Low Mass

We measured gas-phase metallicity, ionisation parameter, and dust extinction for a representative sample of 1795 local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by comparing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [S III]λλ9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. However, we find that current photoionisation model predictions substantially over-predict the intensity of the [S III] lines, while broadly reproducing other observed optical line ratios. We discuss how to nonetheless make use of the information provided by the [S III] lines by setting a prior on the ionisation parameter. Following this approach, we derive spatially resolved maps and radial profiles of metallicity and ionisation parameter. The metallicity radial profiles derived are comparable with previous works, with metallicity declining toward the outer parts and showing a flattening in the central regions. This is in agreement with infall models of galaxy formation, which predict that spiral discs build up through accretion of material, leading to an inside-out growth. On the other hand, ionisation parameter radial profiles are flat for low-mass galaxies, while their slope becomes positive as galaxy mass increases. However, the ionisation parameter maps we obtain are clumpy, especially for low-mass galaxies. The ionisation parameter is tightly correlated with the equivalent width of Hα [EW(Hα)], following a nearly universal relation, which we attribute to the change of the spectral shape of ionising sources due to ageing of H II regions. We derive a positive correlation between ionisation parameter and metallicity at fixed EW(Hα), in disagreement with previous theoretical work that predict an anti-correlation.

scholarly journals The Pristine Survey – VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime

2020 ◽  
Vol 492 (4) ◽  
pp. 4986-5002 ◽  
Author(s):  
K Youakim ◽  
E Starkenburg ◽  
N F Martin ◽  
G Matijevič ◽  
D S Aguado ◽  
...  
Keyword(s):  
Distribution Function ◽  
Globular Clusters ◽  
Milky Way ◽  
Current Data ◽  
Low Latitude ◽  
Chemical Enrichment ◽  
Merger Event ◽  
Low Metallicity ◽  
Metallicity Distribution ◽  
Milky Way Halo

ABSTRACT The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ($ \rm [Fe/H] \lt -3$), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2500\, \mathrm{deg}^2$. We focus our analysis on a subsample of ∼80 000 main-sequence turn-off stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at $ \rm [Fe/H] =-1.6$, and a slope of Δ(LogN)/$\Delta \rm [Fe/H] = 1.0 \pm 0.1$ in the metallicity range of $-3.4\; \lt\; \rm [Fe/H]\; \lt -2.5$. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low-latitude field in the anticentre direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for $ \rm [Fe/H]\; \lt\; -2.5$ and 1.5 for $ \rm [Fe/H]\; \lt\; -3$, suggesting that the lack of low-metallicity globular clusters in the Milky Way is not due simply to statistical undersampling.

Tracking a Long-Lasting Outer Tropical Cyclone Rainband: Origin and Convective Transformation

2019 ◽  
Vol 76 (10) ◽  
pp. 3267-3283 ◽  
Author(s):  
Cheng-Ku Yu ◽  
Che-Yu Lin ◽  
Jhang-Shuo Luo
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Radial Distance ◽  
Vertical Shear ◽  
Convective Precipitation ◽  
Squall Line ◽  
Mature Stage ◽  
Clear Trend ◽  
Dynamical Interaction ◽  
Cold Pools

Abstract This study used radar and surface observations to track a long-lasting outer tropical cyclone rainband (TCR) of Typhoon Jangmi (2008) over a considerable period of time (~10 h) from its formative to mature stage. Detailed analyses of these unique observations indicate that the TCR was initiated on the eastern side of the typhoon at a radial distance of ~190 km as it detached from the upwind segment of a stratiform rainband located close to the inner-core boundary. The outer rainband, as it propagated cyclonically outward, underwent a prominent convective transformation from generally stratiform precipitation during the earlier period to highly organized, convective precipitation during its mature stage. The transformation was accompanied by a clear trend of surface kinematics and thermodynamics toward squall-line-like features. The observed intensification of the rainband was not simply related to the spatial variation of the ambient CAPE or potential instability; instead, the dynamical interaction between the prerainband vertical shear and cold pools, with progression toward increasingly optimal conditions over time, provides a reasonable explanation for the temporal alternation of the precipitation intensity. The increasing intensity of cold pools was suggested to play an essential role in the convective transformation for the rainband. The propagation characteristics of the studied TCR were distinctly different from those of wave disturbances frequently documented within the cores of tropical cyclones; however, they were consistent with the theoretically predicted propagation of convectively generated cold pools. The convective transformation, as documented in the present case, is anticipated to be one of the fundamental processes determining the evolving and structural nature of outer TCRs.

Local and Average Heat Transfer Characteristics for a Disk Situated Perpendicular to a Uniform Flow

1985 ◽  
Vol 107 (2) ◽  
pp. 321-326 ◽  
Author(s):  
E. M. Sparrow ◽  
G. T. Geiger
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stagnation Point ◽  
Radial Distance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Average Heat ◽  
Radial Profiles

Wind tunnel experiments were performed to determine both the average heat transfer coefficient and the radial distribution of the local heat transfer coefficient for a circular disk facing a uniform oncoming flow. The experiments covered the range of Reynolds numbers Re from 5000 to 50,000 and were performed using the naphthalene sublimation technique. To complement the experiments, an analysis incorporating both potential flow theory and boundary layer theory was used to predict the stagnation point heat transfer. The measured average Nusselt numbers definitively resolved a deep disparity between information from the literature and yielded the correlation Nu = 1.05 Pr0.36 Re1/2. The radial distributions of the local heat transfer coefficient were found to be congruent when they were normalized by Re1/2. Furthermore, the radial profiles showed that the local coefficient takes on its minimum value at the stagnation point and increases with increasing radial distance from the center of the disk. At the outer edge of the disk, the coefficient is more than twice as large as that at the stagnation point. The theoretical predictions of the stagnation point heat transfer exceeded the experimental values by about 6 percent. This overprediction is similar to that which occurs for cylinders and spheres in crossflow.

scholarly journals Instabilities of Uniformly Rotating Disks

1996 ◽  
Vol 169 ◽  
pp. 349-350 ◽  
Author(s):  
P. Vauterin ◽  
H. Dejonghe
Keyword(s):  
Distribution Function ◽  
Differential Rotation ◽  
Mass Concentration ◽  
Expansion Method ◽  
Rotating Disks ◽  
Central Mass ◽  
Reasonable Approximation ◽  
Central Regions ◽  
Series Expansion Method

We explore a series expansion method to calculate the instabilities and the structure of the perturbations for a variety of uniformly rotating finite stellar disks. This survey focuses on the role of the distribution function in stability analyses. Although the potential does not show differential rotation, it will in many cases be a reasonable approximation for the disk in the central regions of galaxies without massive central mass concentration.

Evidence for the homothetic scaling of urban forms

2018 ◽  
Vol 47 (5) ◽  
pp. 870-888 ◽  
Author(s):  
Rémi Lemoy ◽  
Geoffrey Caruso
Keyword(s):  
Land Use ◽  
Population Density ◽  
Scaling Laws ◽  
Radial Distance ◽  
Three Dimensions ◽  
City Size ◽  
Cube Root ◽  
Radial Profiles ◽  
Population Grid ◽  
Urban Scaling

The size and form of cities influence their social and environmental impacts. Whether cities have the same form irrespective of their size is still an open question. We analyse the profile of artificial land and population density, with respect to the distance to their main centre, for the 300 largest European cities. Our analysis combines the GMES/Copernicus Urban Atlas 2006 land use database at 5 m resolution for 300 larger urban zones with more than 100,000 inhabitants and the Geostat population grid at 1 km resolution. We find a remarkable constancy of radial profiles across city sizes. Artificial land profiles scale in the two horizontal dimensions with the square root of city population, while population density profiles scale in three dimensions with its cube root. In short, cities of different size are homothetic in terms of land use and population density, which challenges the idea that larger cities are more parsimonious in the use of land per capita. While earlier literature documented the scaling of average densities (total surface and population) with city size, we document the scaling of the whole radial distance profile with city size, thus liaising intra-urban radial analysis and systems of cities. Our findings also yield homogenous spatial definitions of cities, from which we can re-question urban scaling laws and Zipf’s law for cities.

scholarly journals CHEMICAL CARTOGRAPHY WITH APOGEE: METALLICITY DISTRIBUTION FUNCTIONS AND THE CHEMICAL STRUCTURE OF THE MILKY WAY DISK

2015 ◽  
Vol 808 (2) ◽  
pp. 132 ◽  
Author(s):  
Michael R. Hayden ◽  
Jo Bovy ◽  
Jon A. Holtzman ◽  
David L. Nidever ◽  
Jonathan C. Bird ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Milky Way ◽  
Distribution Functions ◽  
Metallicity Distribution

scholarly journals Fossil group origins

2018 ◽  
Vol 618 ◽  
pp. A172 ◽  
Author(s):  
E. M. Corsini ◽  
L. Morelli ◽  
S. Zarattini ◽  
J. A. L. Aguerri ◽  
L. Costantin ◽  
...  
Keyword(s):  
Stellar Population ◽  
Line Strength ◽  
Abundance Ratio ◽  
Element Abundance ◽  
Population Parameters ◽  
Stellar Kinematics ◽  
Massive Galaxies ◽  
Radial Profiles ◽  
Major Merger ◽  
Satellite Galaxies

Context. Fossil groups (FGs) are galaxy aggregates with an extended and luminous X-ray halo, which are dominated by a very massive early-type galaxy and lack of L∗ objects. FGs are indeed characterized by a large magnitude gap between their central and surrounding galaxies. This is explained by either speculating that FGs are failed groups that formed without bright satellite galaxies and did not suffer any major merger, or by suggesting that FGs are very old systems that had enough time to exhaust their bright satellite galaxies through multiple major mergers. Aims. Since major mergers leave signatures in the stellar populations of the resulting galaxy, we study the stellar population parameters of the brightest central galaxies (BCGs) of FGs as a benchmark against which the formation and evolution scenarios of FGs can be compared. Methods. We present long-slit spectroscopic observations along the major, minor, and diagonal axes of NGC 6482 and NGC 7556, which are the BCGs of two nearby FGs. The measurements include spatially resolved stellar kinematics and radial profiles of line-strength indices, which we converted into stellar population parameters using single stellar-population models. Results. NGC 6482 and NGC 7556 are very massive (M∗ ≃ 1011.5 M⊙) and large (D25 ≃ 50 kpc) galaxies. They host a centrally concentrated stellar population, which is significantly younger and more metal rich than the rest of the galaxy. The age gradients of both galaxies are somewhat larger than those of the other FG BCGs studied so far, whereas their metallicity gradients are similarly negative and shallow. Moreover, they have negligible gradients of α-element abundance ratio. Conclusions. The measured metallicity gradients are less steep than those predicted for massive galaxies that formed monolithically and evolved without experiencing any major merger. We conclude that the observed FGs formed through major mergers rather than being failed groups that lacked bright satellite galaxies from the beginning.

scholarly journals Galaxies hosting an active galactic nucleus: a view from the CALIFA survey

2020 ◽  
Vol 492 (3) ◽  
pp. 3073-3090 ◽  
Author(s):  
Eduardo A D Lacerda ◽  
Sebastián F Sánchez ◽  
R Cid Fernandes ◽  
Carlos López-Cobá ◽  
Carlos Espinosa-Ponce ◽  
...  
Keyword(s):  
Star Formation ◽  
Morphological Type ◽  
Molecular Gas ◽  
Main Role ◽  
Type I ◽  
Massive Galaxies ◽  
Star Forming ◽  
Integral Field Spectroscopy ◽  
Almost All ◽  
Formation Efficiency

ABSTRACT We study the presence of optically-selected active galactic nuclei (AGNs) within a sample of 867 galaxies extracted from the extended Calar-Alto Legacy Integral Field spectroscopy Area (eCALIFA) spanning all morphological classes. We identify 10 Type-I and 24 Type-II AGNs, amounting to ∼4 per cent of our sample, similar to the fraction reported by previous explorations in the same redshift range. We compare the integrated properties of the ionized and molecular gas, and stellar population of AGN hosts and their non-active counterparts, combining them with morphological information. The AGN hosts are found in transitory parts (i.e. green-valley) in almost all analysed properties which present bimodal distributions (i.e. a region where reside star-forming galaxies and another with quiescent/retired ones). Regarding morphology, we find AGN hosts among the most massive galaxies, with enhanced central stellar-mass surface density in comparison to the average population at each morphological type. Moreover, their distribution peaks at the Sab-Sb classes and none are found among very late-type galaxies (>Scd). Finally, we inspect how the AGN could act in their hosts regarding the quenching of star-formation. The main role of the AGN in the quenching process appears to be the removal (or heating) of molecular gas, rather than an additional suppression of the already observed decrease of the star-formation efficiency from late-to-early type galaxies.

The Metallicity Distribution Function of Halo Dwarfs and Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 517-518
Author(s):  
J. B. Laird ◽  
M. P. Rupin ◽  
B. W. Carney ◽  
D. W. Latham ◽  
R. L. Kurucz
Keyword(s):  
Distribution Function ◽  
Simple Model ◽  
Chemical Evolution ◽  
Globular Clusters ◽  
Dwarf Stars ◽  
Metallicity Distribution

Metallicities have been determined for a chemically unbiased sample of field halo dwarf stars. Their metallicity distribution function is similar to the predictions of a simple model of chemical evolution, but somewhat different from that of globular clusters.

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