Astronomy & Astrophysics最新文献

{"title":"The PAU Survey: Galaxy stellar population properties estimates with narrowband data","authors":"B. Csizi, L. Tortorelli, M. Siudek, D. Grün, P. Renard, P. Tallada-Crespí, E. Sanchez, R. Miquel, C. Padilla, J. García-Bellido, E. Gaztañaga, R. Casas, S. Serrano, J. De Vicente, E. Fernandez, M. Eriksen, G. Manzoni, C. M. Baugh, J. Carretero, F. Castander","doi":"10.1051/0004-6361/202449838","DOIUrl":"https://doi.org/10.1051/0004-6361/202449838","url":null,"abstract":"A newfound interest has been seen in narrowband galaxy surveys as a promising method for achieving the necessary accuracy on the photometric redshift estimate of individual galaxies for next-generation stage IV cosmological surveys. One key advantage is the ability to provide higher spectral resolution information on galaxies, which ought to allow for a more accurate and precise estimation of the stellar population properties for galaxies. However, the impact of adding narrowband photometry on the stellar population properties estimate is largely unexplored. The scope of this work is two-fold: 1) we leverage the predictive power of broadband and narrowband data to infer galaxy physical properties, such as stellar masses, ages, star formation rates, and metallicities; and 2) we evaluate the improvement of performance in estimating galaxy properties when we use narrowband instead of broadband data. In this work, we measured the stellar population properties of a sample of galaxies in the COSMOS field for which both narrowband and broadband data are available. In particular, we employed narrowband data from the Physics of the Accelerating Universe Survey (PAUS) and broadband data from the Canada France Hawaii Telescope legacy survey (CFHTLS). We used two different spectral energy distribution (SED) fitting codes to measure galaxy properties, namely and We find that the increased spectral resolution of narrowband photometry does not yield a substantial improvement in terms of constraining the galaxy properties using the SED fitting. Nonetheless, we find that we are able to obtain a more diverse distribution of metallicities and dust optical depths with when employing the narrowband data. The effect is not as prominent as expected, which we relate to the low narrowband signal-to-noise ratio (S/N) of a majority of the sampled galaxies, the respective drawbacks of both codes, and the restriction of coverage to the optical regime. The measured properties are compared to those reported in the COSMOS2020 catalogue, showing a good agreement. We have released the catalogue of measured properties in tandem with this work.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 808","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141364000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New ACV variables discovered in the Zwicky Transient Facility survey","authors":"B. Bauer-Fasching, K. Bernhard, E. Brandli, H. Burger, B. Eisele, S. Hummerich, J. Neuhold, E. Paunzen, M. Piecka, S. Ratzenbock, M. Privsegen","doi":"10.1051/0004-6361/202347476","DOIUrl":"https://doi.org/10.1051/0004-6361/202347476","url":null,"abstract":"The manifestation of surface spots on magnetic chemically peculiar (mCP) stars is most commonly explained by the atomic diffusion theory, which requires a calm stellar atmosphere and only moderate rotation. While very successful and well described, this theory still needs to be revised and fine-tuned to the observations. Our study aims to enlarge the sample of known photometrically variable mCP stars (ACV variables) to pave the way for more robust and significant statistical studies. We derive accurate physical parameters for these objects and discuss our results in the framework of the atomic diffusion theory. We studied 1314 candidate ACV variables that were selected from the Zwicky Transient Factory catalogue of periodic variables based on light curve characteristics. We investigated these objects using photometric criteria, a colour-magnitude diagram, and spectroscopic data from the LAMOST and Gaia missions to confirm their status as ACV variables. We present a sample of 1232 new ACV variables, including information on distance from the Sun, mass, fractional age on the main sequence, fraction of the radius between the zero-age and terminal-age main sequence, and the equatorial velocity and its ratio to the critical velocity. Our results confirm that the employed selection process is highly efficient for detecting ACV variables. We have identified 38 stars with $v_ equ $). This challenges current theories that cannot explain the occurrence of such fast-rotating mCP stars.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 32","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141366054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Striving towards robust phase diversity on-sky. Implementing LIFT for VLT/MUSE-NFM","authors":"Arseniy Kuznetsov, S. Oberti, B. Neichel, Thierry Fusco","doi":"10.1051/0004-6361/202449860","DOIUrl":"https://doi.org/10.1051/0004-6361/202449860","url":null,"abstract":"The recent IRLOS upgrade for VLT/MUSE narrow field mode (NFM) introduced a full-pupil mode to enhance sensitivity and sky coverage. This involved replacing the 2times 2 Shack-Hartmann sensor with a single lens for full-aperture photon collection, which also enabled the engagement of the linearized focal-plane technique (LIFT) wavefront sensor instead. However, initial on-sky LIFT experiments have highlighted a complex point spread function (PSF) structure due to strong and polychromatic non-common path aberrations (NCPAs), complicating the accurate retrieval of tip-tilt and focus using LIFT. This study aims to conduct the first on-sky validation of LIFT on VLT/UT4, outline challenges encountered during the tests, and propose solutions for increasing the robustness of LIFT in on-sky operations. We developed a two-stage approach to focal-plane wavefront sensing, where tip-tilt and focus retrieval done with LIFT is preceded by the NCPA calibration step. The resulting NCPA estimate is subsequently used by LIFT. To perform the calibration, we proposed a method capable of retrieving the information about NCPAs directly from on-sky focal-plane PSFs. We verified the efficacy of this approach in simulated and on-sky tests. Our results demonstrate that adopting the two-stage approach has led to a significant improvement in the accuracy of the defocus estimation performed by LIFT, even under challenging low-flux conditions. The efficacy of LIFT as a slow and truth focus sensor in practical scenarios has been demonstrated. However, integrating NCPA calibration with LIFT is essential to verifying its practical application in the real system. Additionally, the proposed calibration step can serve as an independent and minimally invasive approach to evaluate NCPA on-sky.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 809","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141363999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Apparent non-variable stars from the Kepler mission","authors":"E. Paunzen, F. Binder, A. Cyniburk, M. N. Duffek, F. Haberhauer, C. Heinreichsberger, H. Kohlhofer, L. Kuess, H. Maitzen, T. Saalmann, A. M. Schanz, S. Schauer, K. Schmidt, A. Tokareva, I. Wizani","doi":"10.1051/0004-6361/202244572","DOIUrl":"https://doi.org/10.1051/0004-6361/202244572","url":null,"abstract":"The analysis of non-variable stars is generally neglected in the literature. However, such objects are needed for many calibration processes and for testing pulsational models. The photometric time series of the Kepler satellite mission still stand as the most accurate data available today and are excellently suited to the search for non-variable stars. We analysed all long-cadence light curves for stars not reported as a variable so far from the Kepler satellite mission. Using the known characteristics and flaws of these data sets, we defined three different frequency ranges where we searched for non-variability. We used the Lomb-Scargle periodogram and the false-alarm probability (FAP) to analyse the cleaned data sets of light curves. We then used $ FAP -2$ to define a star as 'non-variable' in the ranges below 0.1,c/d, 0.1 to 2.0,c/d, and 2.0 to 25.0,c/d, respectively. Furthermore, we also calculated the standard deviation of the mean light curve to obtain another parameter. In total, we found stars that fulfil the set criteria. These objects are mostly cooler than the K populating the whole main sequence (MS) to the red giant branch (RGB).","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141363884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detecting galaxy groups populating the local Universe in the eROSITA era","authors":"I. Marini, P. Popesso, G. Lamer, K. Dolag, V. Biffi, S. Vladutescu-Zopp, A. Dev, V. Toptun, E. Bulbul, J. Comparat, N. Malavasi, A. Merloni, T. Mroczkowski, G. Ponti, R. Seppi, S. Shreeram, Y. Zhang","doi":"10.1051/0004-6361/202450442","DOIUrl":"https://doi.org/10.1051/0004-6361/202450442","url":null,"abstract":"eROSITA will deliver an unprecedented volume of X-ray survey observations, $20-30$ times more sensitive than ROSAT in the soft band ($0.5-2.0$ keV) and for the first time imaging in the hard band ($2-10$ keV). The final observed catalogue of sources will include galaxy clusters and groups along with obscured and unobscured ( active galactic nuclei ) AGNs. This calls for a powerful theoretical effort to mitigate potential systematics and biases that may influence the data analysis. We investigate the detection technique and selection biases in the galaxy group and AGN populations within a simulated X-ray observation conducted at the depth equivalent to a four-year eROSITA survey (eRASS:4). We generate a mock observation spanning $30 30$ deg2 based on the cosmological hydrodynamical simulation Magneticum Pathfinder from $z=0$ up to redshift $z=0.2$, mirroring the depth of eRASS:4 (with an average exposure of$ 600$ s). We combined a physical background from the real eFEDS background analysis with realistic simulations of X-ray emission for the hot gas, AGNs, and XRB. Using a detection method similar to that utilised for eRASS data, we assessed completeness and contamination levels to reconstruct the luminosity functions for both extended and point sources within the catalogue. We define the completeness of extended detections as a function of the input X-ray flux $S_ $ and halo mass $M_ $ at the depth of eRASS:4. Notably, we fully recovered the brightest (most massive) galaxy clusters and AGNs. However, a significant fraction of galaxy groups ($M_ M_ odot $) remain undetected. Examining gas properties between the detected and undetected galaxy groups at a fixed halo mass, we observe that the detected population typically displays higher X-ray brightness compared to the undetected counterpart. Furthermore, we establish that X-ray luminosity primarily correlates with the hot gas fraction, rather than temperature or metallicity. Our simulation suggests a systematic selection bias in current surveys, leading to X-ray catalogues predominantly composed of the lowest-entropy, gas-richest, and highest surface brightness halos on galaxy group scales.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 984","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141364240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detailed chemical abundances of the globular cluster Terzan 6 in the inner bulge","authors":"C. Fanelli, L. Origlia, A. Mucciarelli, F. Ferraro, R. M. Rich, B. Lanzoni, D. Massari, C. Pallanca, E. Dalessandro, M. Loriga","doi":"10.1051/0004-6361/202450556","DOIUrl":"https://doi.org/10.1051/0004-6361/202450556","url":null,"abstract":"We used near-infrared spectroscopy at medium-high resolution (R=8,000$-$25,000) to perform the first comprehensive chemical study of the intermediate luminosity bulge globular cluster Terzan 6. \u0000We derived detailed abundances and abundance patterns of 27 giant stars, likely members of Terzan 6, based on their accurate Hubble Space Telescope proper motions and line-of-sight radial velocities. \u0000From the spectral analysis of these stars, we determined an average heliocentric radial velocity of 143.3pm 1.0 km s$^ $ with a velocity dispersion of 5.1pm 0.7 km s$^ $ and an average Fe/H and a low 1sigma dispersion of 0.03 dex. We also measured some depletion of Mn/Fe with respect to the solar-scaled values and \u0000enhancement of for Ca/Fe Si/Fe Mg/Fe Ti/Fe O/Fe Al/Fe Na/Fe and, to a lower extent, for K/Fe consistent with previous measurements of other bulge globular clusters \u0000and favoring the scenario of a rapid bulge formation and chemical enrichment.\u0000Some spread in the light element abundances suggest the presence of first- and second-generation stars, typical of genuine globulars.\u0000Finally, we measured some depletion of carbon and low $ C/^ C$ isotopic ratios, \u0000as in previous studies of field and cluster bulge giants, indicating that extra-mixing mechanisms \u0000should be at work during the post main sequence evolution in the high metallicity regime as well.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 17","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141370888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ExoplANETS-A: A virtual observatory database for host stars and planetary systems. The effect of XUV on planet atmospheres","authors":"M. Morales-Calderon, S.R.G. Joyce, J. Pye, D. Barrado, M. Garcia, Castro, C. Rodrigo, E. Solano, J. D. Nichols, P. Lagage, A. Castro-González, R. A. Garcia, M. Guedel, N. Huelamo, Y. Metodieva, R. Waters","doi":"10.1051/0004-6361/202449832","DOIUrl":"https://doi.org/10.1051/0004-6361/202449832","url":null,"abstract":"ExoplANETS-A is an EU Horizon-2020 project with the primary objective of establishing new knowledge on exoplanet atmospheres. Intimately related to this topic is the study of the host stars' radiative properties in order to understand the environment in which exoplanets lie. The aim of this work is to exploit archived data from space-based observatories and other public sources to produce uniform sets of stellar data that can establish new insight into the influence of the host star on the planetary atmosphere. We have compiled X-ray and UV luminosities, which affect the formation and the atmospheric properties of the planets, and stellar parameters, which impact the retrieval process of the planetary atmosphere's properties and its errors. Our sample is formed of all transiting-exoplanet systems observed by HST or Spitzer . It includes 205 exoplanets and their 114 host stars. We have built a catalogue with information extracted from public, online archives augmented by quantities derived by the Exoplanets-A work. With this catalogue we have implemented an online database that also includes X-ray and OHP spectra and TESS light curves. In addition, we have developed a tool, exoVOSA, that is able to fit the spectral energy distribution of exoplanets. We give an example of using the database to study the effects of the host star high energy emission on the exoplanet atmosphere. The sample has a planet radius valley that is located at 1.8 $ R_ oplus $, in agreement with previous studies. Multiplanet systems in our sample were used to test the photoevaporation model and we find that out of 14 systems, only one significant case poses a contradiction to it (K2-3). In this case, the inner planet of the system is above the radius gap while the two exterior planets are both below it. This indicates that some factor not included in the photoevaporation model has increased the mass-loss timescale of the inner planet. In summary, the exoplanet and stellar resources compiled and generated by ExoplANETS-A form a sound basis for current JWST observations and for future work in the era of Ariel","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 25","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141372158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-redshift Lyman Continuum Survey (LzLCS): Radio continuum properties of low-z Lyman continuum emitters","authors":"O. Bait, S. Borthakur, D. Schaerer, E. Momjian, Biny Sebastian, A. Saldana-Lopez, S. Flury, J. Chisholm, R. Marques-Chaves, A. Jaskot, H. Ferguson, G. Worseck, Zhiyuan Ji, L. Komarova, M. Trebitsch, M. Hayes, L. Pentericci, G. Ostlin, T. Thuan, Bingjie Wang, Xinfeng Xu, M. Sargent","doi":"10.1051/0004-6361/202348416","DOIUrl":"https://doi.org/10.1051/0004-6361/202348416","url":null,"abstract":"Sources that leak Lyman continuum (LyC) photons and lead to the reionisation of the universe are an object of intense study using multiple observing facilities. Recently the Low-redshift LyC Survey (LzLCS) has presented the first large sample of LyC emitting galaxies at low redshift ($z 0.3$) with the Hubble Space Telescope Cosmic Origins Spectrograph . The LzLCS sample contains a robust estimate of the LyC escape fraction ( ) for 66 galaxies, spanning a wide range of values. Here, we aim to study the dependence of on the radio continuum (RC) properties of LzLCS sources. Overall, RC emission can provide unique insights into the role of supernova feedback, cosmic rays (CRs), and magnetic fields from its non-thermal emission component. RC emission is also a dust-free tracer of the star formation rate (SFR) in galaxies. In this study, we present Karl G. Jansky Very Large Array (VLA) RC observations of the LzLCS sources at gigahertz (GHz) frequencies. We performed VLA C (4-8 GHz) and S (2-4 GHz) band observations for a sample of 53 LzLCS sources. We also observed a sub-sample of 17 LzLCS sources in the L (1-2 GHz) band. We detected RC from both C- and S-bands in 24 sources for which we are able to estimate their radio spectral index across 3-6 GHz, denoted as . We also used the RC luminosity to estimate their SFRs. The radio spectral index of LzLCS sources spans a wide range, from flat ( $ -0.1$) to very steep ($ -1.0$). They have a steeper mean -0.92$) compared to that expected for normal star-forming galaxies ( -0.64$). They also show a larger scatter in (sim 0.71) compared to that of normal star-forming galaxies (sim 0.15). \u0000 The strongest leakers in our sample show flat weak leakers have close to normal star-forming galaxies and non-leakers are characterized by steep .\u0000 We argue that a combination of young ages, free-free absorption, and a flat cosmic-ray energy spectrum can altogether lead to a flat for strong leakers. Non-leakers are characterized by steep spectra which can arise due to break or cutoff at high frequencies. Such a cutoff in the spectrum can arise in a single injection model of CRs characteristic of galaxies which have recently stopped star-formation. The dependence of on (which is orientation-independent) suggests that the escape of LyC photons is not highly direction-dependent at least to the first order.\u0000 \u0000 The radio-based SFRs ( ) of LzLCS sources show a large offset ($ dex) from the standard calibration. We find that adding as a second parameter helps us to calibrate the with and within a scatter of $ dex. For the first time, we have found a relation between and . This hints at the interesting role of supernovae feedback, CRs, and magnetic fields in facilitating the escape (alternatively, and/or the lack) of LyC photons.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141372458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quasars as standard candles VI. Spectroscopic validation of the cosmological sample","authors":"B. Trefoloni, E. Lusso, E. Nardini, G. Risaliti, A. Marconi, G. Bargiacchi, Andrea Sacchi, Paola Pietrini, M. Signorini","doi":"10.1051/0004-6361/202348938","DOIUrl":"https://doi.org/10.1051/0004-6361/202348938","url":null,"abstract":"A sample of quasars has been recently assembled to investigate the non-linear relation between their monochromatic luminosities at 2500 and 2 keV and to exploit quasars as a new class of `standardized candles'. The use of this technique for cosmological purposes relies on the non-evolution with redshift of the UV-optical spectral properties of quasars, as well as on the absence of possible contaminants such as dust extinction and host galaxy contribution. We address these possible issues by analysing the spectral properties of our cosmological quasar sample. We produced composite spectra in different bins of redshift and accretion parameters (black hole mass, bolometric luminosity), to investigate any possible evolution of the spectral properties of the continuum of the composites with these parameters. We found a remarkable similarity amongst the various stacked spectra. Apart from the well known evolution of the emission lines with luminosity (i.e. the Baldwin effect) and black hole mass (i.e. the virial relation), the overall shape of the continuum, produced by the accretion disc, does not show any statistically significant trend with black-hole mass BH $), bolometric luminosity ($L_ bol $), or redshift ($z$). The composite spectrum of our quasar sample is consistent with negligible levels of both intrinsic reddening (with a colour excess $E(B-V) 0.01$) and host galaxy emission (less than 10) in the optical. We tested whether unaccounted dust extinction could explain the discrepancy between our cosmographic fit of the i tre diagram and the concordance $ Lambda $CDM model. The average colour excess required to solve the tension should increase with redshift up to unphysically high values ($E(B-V) at $z>3$) that would imply that the intrinsic emission of quasars is much bluer and more luminous than ever reported in observed spectra. The similarity of quasar spectra across the parameter space excludes a significant evolution of the average continuum properties with any of the explored parameters, confirming the reliability of our sample for cosmological applications. Lastly, dust reddening cannot account for the observed tension between the i tre diagram of quasars and the $ Lambda $CDM model.","PeriodicalId":505693,"journal":{"name":"Astronomy & Astrophysics","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141375314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photometric classification of stars around the Milky Way's central black hole. I. Central parsec","authors":"E. Gallego-Cano, T. Fritz, R. Schodel, A. Feldmeier-Krause, T. Do, S. Nishiyama","doi":"10.1051/0004-6361/202449881","DOIUrl":"https://doi.org/10.1051/0004-6361/202449881","url":null,"abstract":"The presence of young massive stars in the Galactic Centre (GC) raises questions about how such stars could form near the massive black hole Sagittarius,A* (Sgr,A*). Furthermore, the shape of the initial mass function (IMF) in this region seems to differ from its standard Salpeter/Kroupa law. Due to observational challenges such as extreme extinction and crowding, our understanding of the stellar population in this region remains limited, with spectroscopic data available only for selected small and comparably bright sources. We aim to improve our knowledge about the distribution and the IMF of young, massive, stars in the vicinity of Sgr,A*. We used intermediate band (IB) photometry to identify candidates for massive young stars. To ensure robust classification, we applied three different, but complementary methods: Bayesian inference, a basic neural network, and a fast gradient-boosted trees algorithm. We obtain spectral energy distributions for 6590 stars, 1181 of which have been previously classified spectroscopically. We identify 351 stars that are classified as early types by all three classification methods, with 155 of them being newly identified candidates. The radial density profiles for late and early-type stars fit well with broken power laws, revealing a break radius of $9.2 0.6''$ for early-type stars. The late-type stars show a core-like distribution around Sgr,A* while the density of the early-type stars increases steeply towards the black hole, consistent with previous work. We infer a top-heavy IMF of the young stars near Sgr,A* ($R < 9''$), with a power-law of $1.6 0.1$. At greater distances from Sgr,A* a standard Salpeter/Kroupa IMF can explain the data. Additionally, we demonstrate that IB photometry can also constrain the metallicities of late-type stars, estimating metallicities for over 600 late-type stars. The variation of the IMF with radial distance from Sgr,A* suggests that different mechanisms of star formation may have been at work in this region. The top-heavy IMF in the innermost region is consistent with star formation in a disc around Sgr,A*.","PeriodicalId":505693,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"162 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141376214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}