The Stellar Halo Metallicity - Luminosity Relationship for Spiral Galaxies

The stellar halos of spiral galaxies bear important chemo-dynamical signatures of galaxy formation. We present here the analysis of 89 semi-cosmological spiral galaxy simulations, spanning ~ 4 magnitudes in total galactic luminosity. These simulations sample a wide variety of merging histories and show significant dispersion in halo metallicity at a given total luminosity - more than a factor of ten in metallicity. Our preliminary analysis suggests that galaxies with a more extended merging history possess halos which have younger and more metal rich stellar populations than the stellar halos associated with galaxies with a more abbreviated assembly. A correlation between halo metallicity and its surface brightness has also been found, reflecting the correlation between halo metallicity and its stellar mass. Our simulations are compared with recent Hubble Space Telescope observations of resolved stellar halos in nearby spirals.Comment: 5 pages, 4 figures. MNRAS Letters, in pres

Hotel customer segmentation and sentiment analysis through online reviews: An analysis of selected European markets [Segmentação de clientes hoteleiros e análise de sentimento através de avaliações online: uma análise de mercados europeus selecionados]

Oliveira, A. S., Renda, A. I., Correia, M. B., & António, N. (2022). Hotel customer segmentation and sentiment analysis through online reviews: An analysis of selected European markets [Segmentação de clientes hoteleiros e análise de sentimento através de avaliações online: uma análise de mercados europeus selecionados]. Tourism & Management Studies, 18(1), 29-40. https://doi.org/10.18089/tms.2022.180----------------------------------------------This paper is financed by National Funds provided by FCTFoundation for Science and Technology through project UIDB/04470/2020This study aims to verify how distinct markets evaluate hotels in the Algarve through the analysis of online reviews, in order to identify if satisfaction and dissatisfaction attributes are similar among some of the main markets of overnight stay tourists in the region. Online reviews of hotels in the Algarve, written in English, French as well as Portuguese and posted on Tripadvisor by British, French and Portuguese residents from January 2019 to December 2019 are analysed. After the analysis of 8,596 online textual reviews, the results demonstrated that not only satisfaction and dissatisfaction rates towards hotel attributes differ according to the language, but also that customers from different countries place dissimilar emphasis on hotel attributes. Besides extending the current research on the use of online reviews, the findings of this study also assist hoteliers to identify improvement opportunities. Although many studies on marketing segmentation through data mining have been conducted, this paper analyses the customer satisfaction of relevant tourist markets and suggests up-to-date practical implications for hoteliers. --------------------------------------------------------------------------------------- Este estudo tem como objetivo verificar como mercados distintos avaliam hotéis no Algarve através da análise de comentários online, a fim de identificar se os atributos de satisfação e insatisfação são semelhantes entre alguns dos principais mercados turísticos da região. São analisadas avaliações online de hotéis no Algarve, escritas em inglês, francês e português e publicadas no Tripadvisor por residentes britânicos, franceses e portugueses de janeiro de 2019 a dezembro de 2019. Após a análise de 8.596 avaliações textuais online, os resultados demonstraram que não apenas as taxas de satisfação e insatisfação em relação aos atributos hoteleiros diferem de acordo com a língua, mas também que clientes de diferentes países colocam ênfase diferente nos atributos do hotel. Além de ampliar a pesquisa atual sobre o uso de revisões online, os resultados deste estudo também auxiliam os hoteleiros a identificar oportunidades de melhoria. Embora muitos estudos sobre segmentação de marketing por meio da mineração de dados tenham sido realizados, este artigo analisa a satisfação dos clientes dos mercados turísticos relevantes e sugere implicações práticas atualizadas para os hoteleirospublishersversionpublishe

The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)

We present spectroscopic observations of red giant branch (RGB) stars over a large expanse in the halo of the Andromeda spiral galaxy (M31), acquired with the DEIMOS instrument on the Keck II 10-m telescope. Using a combination of five photometric/spectroscopic diagnostics -- (1) radial velocity, (2) intermediate-width DDO51 photometry, (3) Na I equivalent width (surface gravity sensitive), (4) position in the color-magnitude diagram, and (5) comparison between photometric and spectroscopic [Fe/H] estimates -- we isolate over 250 bona fide M31 bulge and halo RGB stars located in twelve fields ranging from R = 12-165kpc from the center of M31 (47 of these stars are halo members with R > 60 kpc). We derive the photometric and spectroscopic metallicity distribution function of M31 RGB stars in each of these fields. The mean of the resulting M31 spheroid (bulge and halo) metallicity distribution is found to be systematically more metal-poor with increasing radius, shifting from = -0.47+/-0.03 (sigma = 0.39) at R = -0.94+/-0.06 (sigma = 0.60) at R ~ 30 kpc to = -1.26+/-0.10 (sigma = 0.72) at R > 60 kpc, assuming [alpha/Fe] = 0.0. These results indicate the presence of a metal-poor RGB population at large radial distances out to at least R = 160 kpc, thereby supporting our recent discovery of a stellar halo in M31: its halo and bulge (defined as the structural components with R^{-2} power law and de Vaucouleurs R^{1/4} law surface brightness profiles, respectively) are shown to have distinct metallicity distributions. If we assume an alpha-enhancement of [alpha/Fe] = +0.3 for M31's halo, we derive = -1.5+/-0.1 (sigma = 0.7). Therefore, the mean metallicity and metallicity spread of this newly found remote M31 RGB population are similar to those of the Milky Way halo.Comment: Accepted for publication in ApJ on May 4th, 2006 (submitted on Jan 30, 2006). 16 pages, 13 figures, 3 table

Prone positioning and convalescent plasma therapy in a critically ill pregnant woman with COVID-19

Prone positioning is feasible in pregnancy and may have contributed to the positive outcome in this case. Doctors should not be reluctant to move a patient to a prone position just because they are pregnant

The Milky Way: An Exceptionally Quiet Galaxy; Implications for the formation of spiral galaxies

[Abridged]We compare both the Milky Way and M31 galaxies to local external disk galaxies within the same mass range, using their relative locations in the planes formed by V_flat versus M_K, j_disk, and the average Fe abundance of stars in the galaxy outskirts. We find, for all relationships, that the MW is systematically offset by ~ 1 sigma, showing a significant deficiency in stellar mass, in angular momentum, in disk radius and [Fe/H] in the stars in its outskirts at a given V_flat. On the basis of their location in the M_K, V_flat, and R_d volume, the fraction of spirals like the MW is 7+/-1%, while M31 appears to be a "typical'' spiral. Our Galaxy appears to have escaped any significant merger over the last ~10 Gyrs which may explain why it is deficient by a factor 2 to 3 in stellar mass, angular momentum and outskirts metallicity and then, unrepresentative of the typical spiral. As with M31, most local spirals show evidence for a history shaped mainly by relatively recent merging. We conclude that the standard scenario of secular evolution is generally unable to reproduce the properties of most (if not all) spiral galaxies. However, the so-called "spiral rebuilding'' scenario proposed by Hammer et al. 2005 is consistent with the properties of both distant galaxies and of their descendants - the local spirals.Comment: 14 pages, 6 figures, to appear in Ap

Photometric Properties of White Dwarf Dominated Halos

Using stellar population synthesis techniques, we explore the photometric signatures of white dwarf progenitor dominated galactic halos, in order to constrain the fraction of halo mass that may be locked-up in white dwarf stellar remnants. We first construct a 10^9 M_sun stellar halo using the canonical Salpeter initial stellar mass distribution, and then allow for an additional component of low- and intermediate-mass stars, which ultimately give rise to white dwarf remnants. Microlensing observations towards the Large Magellanic Cloud, coupled with several ground-based proper motion surveys, have led to claims that in excess of 20% of the dynamical mass of the halo (10^12 M_sun) might be found in white dwarfs. Our results indicate that (1) even if only 1% of the dynamical mass of the dark halo today could be attributed to white dwarfs, their main sequence progenitors at high redshift (z ~ 3) would have resulted in halos more than 100 times more luminous than those expected from conventional initial mass functions alone, and (2) any putative halo white dwarf progenitor dominated initial mass function component, regardless of its dynamical importance, would be virtually impossible to detect at the present-day, due to its extremely faint surface brightness.Comment: 4 pages, Refereed contribution to the 5th Galactic Chemodynamics conference held in Swinburne, July 2003. Accepted for publication in PAS

The new Checklist of the Italian Fauna: marine Mollusca.

The mollusc fauna of the Mediterranean Sea is still considered as the best-known marine mollusc fauna in the world. The previous modern checklists of marine Mollusca were produced by joint teams of amateurs and professionals. During the last years the Italian Society of Malacology (Società Italiana di Malacologia – S.I.M.) maintained an updated version of the Mediterranean checklist, that served as the backbone for the development of the new Italian checklist. According to the current version (updated on April 1st, 2021), 1,777 recognised species of marine molluscs are present in the Italian Economic Exclusive Zone, including also the Tyrrhenian coasts of Corsica and the continental shelf of the Maltese archipelago. The new checklist shows an increase of 17% of the species reported in the 1995 Checklist. This is largely (yet not solely) due to the new wave of studies based on Integrative Taxonomy approaches. A total of 135 species (7.6%) are strictly endemic to the Italian waters; 44 species (2.5%) are alien and correspond to the 28% of the Mediterranean alien marine molluscs. All eight extant molluscan classes are represented. The families represented in the Italian fauna are 307, an increase of 14.6% from the first checklist, partly due to new records and partly to new phylogenetic systematics. Compared with the whole Mediterranean malacofauna, the Italian component represents 71% in species and 61% in families, which makes it a very remarkable part of the Mediterranean fauna

MaGICC baryon cycle: the enrichment history of simulated disc galaxies

Using cosmological galaxy formation simulations from the MaGICC (Making Galaxies in a Cosmological Context) project, spanning stellar mass from ∼107 to 3 × 1010 M⊙, we trace the baryonic cycle of infalling gas from the virial radius through to its eventual participation in the star formation process. An emphasis is placed upon the temporal history of chemical enrichment during its passage through the corona and circumgalactic medium. We derive the distributions of time between gas crossing the virial radius and being accreted to the star-forming region (which allows for mixing within the corona), as well as the time between gas being accreted to the star-forming region and then ultimately forming stars (which allows for mixing within the disc). Significant numbers of stars are formed from gas that cycles back through the hot halo after first accreting to the star-forming region. Gas entering high-mass galaxies is pre-enriched in low-mass proto-galaxies prior to entering the virial radius of the central progenitor, with only small amounts of primordial gas accreted, even at high redshift (z ∼ 5). After entering the virial radius, significant further enrichment occurs prior to the accretion of the gas to the star-forming region, with gas that is feeding the star-forming region surpassing 0.1 Z⊙ by z = 0. Mixing with halo gas, itself enriched via galactic fountains, is thus crucial in determining the metallicity at which gas is accreted to the disc. The lowest mass simulated galaxy (Mvir ∼ 2 × 1010 M⊙, with M⋆ ∼ 107 M⊙), by contrast, accretes primordial gas through the virial radius and on to the disc, throughout its history. Much like the case for classical analytical solutions to the so-called ‘G-dwarf problem’, overproduction of low-metallicity stars is ameliorated by the interplay between the time of accretion on to the disc and the subsequent involvement in star formation – i.e. due to the inefficiency of star formation. Finally, gas outflow/metal removal rates from star-forming regions as a function of galactic mass are presented