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CAPOS: the bulge Cluster APOgee Survey IV elemental abundances of the bulge globular cluster NGC 6558
(MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2023-10-20) González-Díaz, D.; Fernández-Trincado, J. G.; Villanova, S.; Geisler, D.; Barbuy, B.; Minniti, D.; Beers, T. C.; Bidin, C. M.; Mauro, F.; Muñoz, C.; Tang, B. T.; Soto, M.; Monachesi, A.; Lane, R. R.; Frelijj, H.
This study presents the results concerning six red giant stars members of the globular cluster NGC 6558. Our analysis utilized high-resolution near-infrared spectra obtained through the CAPOS initiative (the APOgee Surv e y of Clusters in the Galactic Bulge), which focuses on surv e ying clusters within the Galactic Bulge, as a component of the Apache Point Observatory Galactic Evolution Experiment II surv e y (APOGEE-2). We employ the Brussels Automatic Code for Characterizing High accUracy Spectra ( BACCHUS ) code to provide line-by-line elemental-abundances for Fe-peak (Fe, Ni), alpha-(O, Mg, Si, Ca, Ti), light-(C, N), odd-Z (Al), and the s-process element (Ce) for the four stars with high-signal-to-noise ratios. This is the first reliable measure of the CNO abundances for NGC 6558. Our analysis yields a mean metallicity for NGC 6558 of ([Fe/H]) = -1.15 +/- 0.08, with no evidence for a metallicity spread. We find a Solar Ni abundance, ([Ni/Fe]) similar to + 0.01, and a moderate enhancement of alpha-elements, ranging between + 0.16 and < + 0.42, and a slight enhancement of the s-process element ([Ce/Fe]) similar to + 0.19. We also found low levels of ([Al/Fe]) similar to + 0.09, but with a strong enrichment of nitrogen, [N/Fe] > + 0.99, along with a low level of carbon, [C/Fe] < -0.12. This behaviour of Nitrogen-Carbon is a typical chemical signature for the presence of multiple stellar populations in virtually all GCs; this is the first time that it is reported in NGC 6558. We also observed a remarkable consistency in the behaviour of all the chemical species compared to the other CAPOS bulge GCs of the same metallicity.
Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus
(IOP Publishing Ltd, 2023/01/01) Cerny, W., Simon, J. D., Li, T. S., Drlica-Wagner, A., Pace, A. B., Martinez-Vazquez, C. E., Riley, A. H., Mutlu-Pakdil, B., Mau, S., Ferguson, P. S., Erkal, D., Munoz, R. R., Bom, C. R., Carlin, J. L., Carollo, D., Choi, Y., Ji, A. P., Manwadkar, V., Martinez-Delgado, D., Miller, A. E., Noel, N. E. D., Sakowska, J. D., Sand, D. J., Stringfellow, G. S., Tollerud, E. J., Vivas, A. K., Carballo-Bello, J. A., Hernandez-Lang, D., James, D. J., Nidever, D. L., Castellon, J. L. Nilo, Olsen, K. A. G., Zenteno, A.
We report the discovery of Pegasus IV, an ultra-faint dwarf galaxy found in archival data from the Dark Energy Camera processed by the DECam Local Volume Exploration Survey. Pegasus IV is a compact, ultra-faint stellar system ( = -r(1/2) 41(-6)(+8) pc, M-V = -4.25 +/- 0.2 mag) located at a heliocentric distance of 90(-6)(+4) kpc. Based on spectra of seven nonvariable member stars observed with Magellan/IMACS, we confidently resolve Pegasus IV's velocity dispersion, measuring s = sigma(v) 3.3(-1.1)(+1.7) km s(-1) (after excluding three velocity outliers), this implies a mass-to-light ratio of M1/2LV ,(1/2)=167(-99)(+224) M-?/L-? for the system. From the five stars with the highest signal-to-noise spectra, we also measure a systemic metallicity of [Fe/H] = -2.63(-0.30)(+0.26) dex, making Pegasus IV one of the most metal-poor ultra-faint dwarfs. We tentatively resolve a nonzero metallicity dispersion for the system. These measurements provide strong evidence that Pegasus IV is a dark-matter-dominated dwarf galaxy, rather than a star cluster. We measure Pegasus IV's proper motion using data from Gaia Early Data Release 3, finding (mu(alpha*, mu delta)) = (0.33 +/- 0.07, -0.21 +/- 0.08) mas yr(-1). When combined with our measured systemic velocity, this proper motion suggests that Pegasus IV is on an elliptical, retrograde orbit, and is currently near its orbital apocenter. Lastly, we identify three potential RR Lyrae variable stars within Pegasus IV, including one candidate member located more than 10 half-light radii away from the system's centroid. The discovery of yet another ultra-faint dwarf galaxy strongly suggests that the census of Milky Way satellites is still incomplete, even within 100 kpc.
Bulge-disc decomposition of the Hydra cluster galaxies in 12 bands
(OXFORD UNIV PRESS, 2023/01/01) Lima-Dias, Ciria, Monachesi, Antonela, Torres-Flores, Sergio, Cortesi, Arianna, Hernandez-Lang, Daniel, P. Montaguth, Gissel, Jimenez-Teja, Yolanda, Panda, Swayamtrupta, Menendez-Delmestre, Karin, Goncalves, Thiago S., Mendez-Hernandez, Hugo, Telles, Eduardo, Dimauro, Paola, Bom, Clecio R., de Oliveira, Claudia Mendes, Kanaan, Antonio, Ribeiro, Tiago, Schoenell, William
When a galaxy falls into a cluster, its outermost parts are the most affected by the environment. In this paper, we are interested in studying the influence of a dense environment on different galaxy's components to better understand how this affects the evolution of galaxies. We use, as laboratory for this study, the Hydra cluster which is close to virialization, yet it still shows evidence of substructures. We present a multiwavelength bulge-disc decomposition performed simultaneously in 12 bands from S-PLUS (Southern Photometric Local Universe Survey) data for 52 galaxies brighter than m(r) = 16. We model the galaxies with a Sersic profile for the bulge and an exponential profile for the disc. We find that the smaller, more compact, and bulge-dominated galaxies tend to exhibit a redder colour at a fixed stellar mass. This suggests that the same mechanisms (ram-pressure and tidal stripping) that are causing the compaction in these galaxies are also causing them to stop forming stars. The bulge size is unrelated to the galaxy's stellar mass, while the disc size increases with greater stellar mass, indicating the dominant role of the disc in the overall galaxy mass-size relation found. Furthermore, our analysis of the environment unveils that quenched galaxies are prevalent in regions likely associated with substructures. However, these areas also harbour a minority of star-forming galaxies, primarily resulting from galaxy interactions. Lastly, we find that similar to 37 per cent of the galaxies exhibit bulges that are bluer than their discs, indicative of an outside-in quenching process in this type of dense environments.
Pre-main-sequence Brackett Emitters in the APOGEE DR17 Catalog: Line Strengths and Physical Properties of Accretion Columns
(IOP Publishing Ltd, 2023/01/01) Campbell, Hunter, Khilfeh, Elliott, Covey, Kevin R., Kounkel, Marina, Ballantyne, Richard, Corey, Sabrina, Roman-Zuniga, Carlos G., Hernandez, Jesus, Martinez, Ezequiel Manzo, Ramirez, Karla Pena, Roman-Lopes, Alexandre, Stassun, Keivan G., Stringfellow, Guy S., Borissova, Jura, Chojnowski, S. Drew, Ramirez-Preciado, Valeria, Kim, Jinyoung Serena, Serna, Javier, Stutz, Amelia M., Lopez-Valdivia, Ricardo, Suarez, Genaro, Ybarra, Jason E., Longa-Pena, Penelope, Fernandez-Trincado, Jose G.
Very young (t less than or similar to 10 Myr) stars possess strong magnetic fields that channel ionized gas from the interiors of their circumstellar disks to the surface of the star. Upon impacting the stellar surface, the shocked gas recombines and emits hydrogen spectral lines. To characterize the density and temperature of the gas within these accretion streams, we measure equivalent widths of Brackett (Br) 11-20 emission lines detected in 1101 APOGEE spectra of 326 likely pre-main-sequence accretors. For sources with multiple observations, we measure median epoch-to-epoch line strength variations of 10% in Br11 and 20% in Br20. We also fit the measured line ratios to predictions of radiative transfer models by Kwan & Fischer. We find characteristic best-fit electron densities of n ( e ) = 10(11)-10(12) cm(-3), and excitation temperatures that are inversely correlated with electron density (from T similar to 5000 K for n ( e ) similar to 10(12) cm(-3) to T similar to 12,500 K at n ( e ) similar to 10(11) cm(-3)). These physical parameters are in good agreement with predictions from modeling of accretion streams that account for the hydrodynamics and radiative transfer within the accretion stream. We also present a supplementary catalog of line measurements from 9733 spectra of 4255 Brackett emission-line sources in the APOGEE Data Release 17 data set.
The isolated elliptical galaxy NGC 5812-MOND or dark matter?
(WILEY-V C H VERLAG GMBH, 2023/01/01) Richtler, Tom, Salinas, Ricardo, Lane, Richard, Hilker, Michael
There exist isolated elliptical galaxies, whose dynamics can be modeled without resorting to dark matter or MOND, for example, NGC 7507. Such objects lack understanding within the current framework of galaxy formation. The isolated elliptical NGC 5812 is another object to investigate a possible role of isolation. We use globular clusters (GCs) and the galaxy light itself as dynamical tracers to constrain its mass profile. We employ Gemini/GMOS mask spectroscopy, apply the GMOS reduction procedures provided within IRAF, measure GC velocities by cross correlation methods and extract the line-of-sight kinematics of galaxy spectra using the tool pPXF. We identify 28 GCs with an outermost galactocentric distance of 20 kpc, for which velocities could be obtained. Furthermore, 16 spectra of the integrated galaxy light out to 6 kpc have been used to model the central kinematics. These spectra provide evidence for a disturbed velocity field, which is plausible given the disturbed morphology of the galaxy. We construct spherical Jeans models for the galaxy light and apply tracer mass estimators for the globular clusters. With the assumptions inherent to the mass estimators, MOND is compatible with the mass out to 20 kpc. However, a dark matter free galaxy is not excluded, given the uncertainties related to a possible nonsphericity and a possible nonequilibrium state. We find one globular cluster with an estimated mass of 1.6x107M circle dot$$ 1.6times 1{0}<^>7{M}_{odot } $$, the first Ultra Compact Dwarf in an isolated elliptical. We put NGC 5812 into the general context of dark matter or alternative ideas in elliptical galaxies. The case for a MONDian phenomenology also among early-type galaxies has become so strong that deviating cases appear astrophysically more interesting than agreements. The baryonic Tully Fisher relation (BTFR) as predicted by MOND is observed in some samples of early-type galaxies, in others not. However, in cases of galaxies that deviate from the MONDian prediction, data quality and data completeness are often problematic.
Colour and infall time distributions of satellite galaxies in simulated Milky-Way analogues
(OXFORD UNIV PRESS, 2023/01/09) Pan, Yue, Simpson, Christine M., Kravtsov, Andrey, Gomez, Facundo A., Grand, Robert J. J., Marinacci, Federico, Pakmor, Rudiger, Manwadkar, Viraj, Esmerian, Clarke J.
We use the Auriga simulations to probe different satellite quenching mechanisms operating at different mass scales (10(5) M-theta ? M * < 10(11) M ((R))) in Milky Way-like hosts. Our goal is to understand the origin of the satellite colour distribution and star-forming properties in both observations and simulations. We find that the satellite populations in the Auriga simulations, which was originally designed to model Milky Way-like host galaxies, resemble the populations in the Exploration of Local VolumE Satellites (ELVES) Surv e y and the Satellites Around Galactic Analogs (SAGA) survey in their luminosity function in the luminosity range -12 ? M-V ? -15 and resemble ELVES in their quenched fraction and colour-magnitude distribution in the luminosity range -12 ? M-g ? -15. We find that satellites transition from blue colours to red colours at the luminosity range -15 ? Mg ? -12 in both the simulations and observations and we show that this shift is driven by environmental effects in the simulations. We demonstrate also that the colour distribution in both simulations and observations can be decomposed into two statistically distinct populations based on their morphological type or star-forming status that are statistically distinct. In the simulations, these two populations also have statistically distinct infall time distributions. The comparison presented here seems to indicate that this tension is resolved by the impro v ed target selection of ELVES, but there are still tensions in understanding the colours of faint galaxies, of which ELVES appears to have a significant population of faint blue satellites not reco v ered in Auriga.
Spatially resolved properties of the ionized gas in the H ii galaxy J084220+115000
(OXFORD UNIV PRESS, 2023/01/09) Fernandez-Arenas, D., Carrasco, E., Terlevich, R., Terlevich, E., Amorin, R., Bresolin, F., Chavez, R., Gonzalez-Moran, A. L., Rosa-Gonzalez, D., Mayya, Y. D., Vega, O., Zaragoza-Cardiel, J., Mendez-Abreu, J., Izazaga-Perez, R., Gil de Paz, A., Gallego, J., Iglesias-Paramo, J., Garcia-Vargas, M. L., Gomez-Alvarez, P., Castillo-Morales, A., Cardiel, N., Pascual, S., Perez-Calpena, A.
We present a spatially resolved spectroscopic study for the metal poor H ii galaxy J084220+115000 using MEGARA Integral Field Unit observations at the Gran Telescopio Canarias. We estimated the gas metallicity using the direct method for oxygen, nitrogen, and helium and found a mean value of 12 + log (O/H) = 8.03 +/- 0.06, and integrated electron density and temperature of similar to 161 cm(-3) and similar to 15400 K, respectively. The metallicity distribution shows a large range of Delta(O/H) = 0.72 dex between the minimum and maximum (7.69 +/- 0.06 and 8.42 +/- 0.05) values, unusual in a dwarf star-forming galaxy. We derived an integrated log (N/O) ratio of -1.51 +/- 0.05 and found that both N/O and O/H correspond to a primary production of metals. Spatially resolved maps indicate that the gas appears to be photoionized by massive stars according to the diagnostic line ratios. Between the possible mechanisms to explain the starburst activity and the large variation of oxygen abundance in this galaxy, our data support a possible scenario where we are witnessing an ongoing interaction triggering multiple star-forming regions localized in two dominant clumps.
Ca triplet metallicities and velocities for 12 globular clusters toward the galactic bulge
(EDP SCIENCES S A, 2023/01/20) Geisler, D., Parisi, M. C., Dias, B., Villanova, S., Mauro, F., Saviane, I., Cohen, R. E., Moni Bidin, C., Minniti, D.
Context. Globular clusters (GCs) are excellent tracers of the formation and early evolution of the Milky Way. The bulge GCs (BGCs) are particularly important because they can reveal vital information about the oldest in situ component of the Milky Way.Aims. Our aim is to derive the mean metallicities and radial velocities for 13 GCs that lie toward the bulge and are generally associated with this component. This region is observationally challenging because of high extinction and stellar density, which hampers optical studies of these and similar BGCs, making most previous determinations of these parameters quite uncertain.Methods. We used near-infrared low-resolution spectroscopy with the FORS2 instrument on the VLT to measure the wavelengths and equivalent widths of the CaII triplet (CaT) lines for a number of stars per cluster. We derived radial velocities, ascertained membership, and applied known calibrations to determine metallicities for cluster members, for a mean of 11 members per cluster. Unfortunately, one of our targets, VVV-GC002, which is the closest GC to the Galactic center, turned out not to have any members in our sample.Results. We derive mean cluster RV values to 3 km s(-1), and mean metallicities to 0.05 dex. We find general good agreement with previous determinations for both metallicity and velocity. On average, our metallicities are 0.07 dex more metal-rich than those of Harris (2010, arXiv:1012.3224), with a standard deviation of the difference of 0.25 dex. Our sample has metallicities between -0.21 and -1.64, and the values are distributed between the traditional metal-rich BGC peak near [Fe/H] -0.5 and a more metal-poor peak around [Fe/H] -1.1, which has recently been identified. These latter are candidates for the oldest GCs in the Galaxy, if blue horizontal branches are present, and include BH 261, NGC 6401, NGC 6540, NGC 6642, and Terzan 9. Finally, Terzan 10 is even more metal-poor. However, dynamically, Terzan 10 is likely an intruder from the halo, possibly associated with the Gaia-Enceladus or Kraken accretion events. Terzan 10 is also confirmed as an Oosterhoff type II GC based on our results.Conclusions. The CaT technique is an excellent method for deriving mean metallicities and velocities for heavily obscured GCs. Our sample provides reliable mean values for these two key properties via spectroscopy of a significant number of members per cluster for this important yet previously poorly studied sample of BGCs. We emphasize that the more metal-poor GCs are excellent candidates for being ancient relics of bulge formation. The lone halo intruder in our sample, Terzan 10, is conspicuous for also having by far the lowest metallicity, and casts doubt on the possibility of any bona fide BGCs at metallicities below about -1.5.
Multiple Populations in Low-mass Globular Clusters: Eridanus
(IOP Publishing Ltd, 2023/02/01) Wang, Yue, Tang, Baitian, Li, Chengyuan, Baumgardt, Holger, Munoz, Ricardo R., Fernandez-Trincado, Jose G., Geisler, Doug, Fang, Yuanqing
Multiple populations (MPs), characterized by variations in light elemental abundances, have been found in stellar clusters in the Milky Way, Magellanic Clouds, as well as several other dwarf galaxies. Based on a large number of observations, mass has been suggested to be a key parameter affecting the presence and appearance of MPs in stellar clusters. To further investigate the existence of MPs in low-mass clusters and explore the mass threshold for the formation of MPs, we carried out a project studying the composition of the stellar population in several lowmass Galactic globular clusters. Here we present our study on the cluster Eridanus. With blue-UV low-resolution spectra obtained with the OSIRIS/Multi-object spectrograph on the Gran Telescopio Canarias, we computed the spectral indices of CH and CN for a sample of giant stars and derived their carbon and nitrogen abundances using model spectra. A significant dispersion in the initial surface abundance of nitrogen was found in the sample, indicating the existence of MPs in Eridanus. Inspecting the age-initial mass distribution of in situ clusters with MPs, we find a slight trend that initial mass increases with increasing age, and the lowest initial masses of logM(initial) similar to 4.98 and 5.26 are found at the young and old end, respectively, which might provide a rough reference for the mass threshold for clusters to form MPs. However, more observations of clusters with low initial masses are still necessary before any firm conclusion can be drawn.
Dusty Starbursts Masquerading as Ultra-high Redshift Galaxies in JWST CEERS Observations
(IOP Publishing Ltd, 2023/02/01) Zavala, Jorge A., Buat, Veronique, Casey, Caitlin M., Finkelstein, Steven L., Burgarella, Denis, Bagley, Micaela B., Ciesla, Laure, Daddi, Emanuele, Dickinson, Mark, Ferguson, Henry C., Franco, Maximilien, Jimenez-Andrade, E. F., Kartaltepe, Jeyhan S., Koekemoer, Anton M., Le Bail, Aurelien, Murphy, E. J., Papovich, Casey, Tacchella, Sandro, Wilkins, Stephen M., Aretxaga, Itziar, Behroozi, Peter, Champagne, Jaclyn B., Fontana, Adriano, Giavalisco, Mauro, Grazian, Andrea, Grogin, Norman A., Kewley, Lisa J., Kocevski, Dale D., Kirkpatrick, Allison, Lotz, Jennifer M., Pentericci, Laura, Perez-Gonzalez, Pablo G., Pirzkal, Nor, Ravindranath, Swara, Somerville, Rachel S., Trump, Jonathan R., Yang, Guang, Yung, L. Y. Aaron, Almaini, Omar, Amorin, Ricardo O., Annunziatella, Marianna, Haro, Pablo Arrabal, Backhaus, Bren E., Barro, Guillermo, Bell, Eric F., Bhatawdekar, Rachana, Bisigello, Laura, Buitrago, Fernando, Calabro, Antonello, Castellano, Marco, Ortiz, Oscar A. Chavez, Chworowsky, Katherine, Cleri, Nikko J., Cohen, Seth H., Cole, Justin W., Cooke, Kevin C., Cooper, M. C., Cooray, Asantha R., Costantin, Luca, Cox, Isabella G., Croton, Darren, Dave, Romeel, de la Vega, Alexander, Dekel, Avishai, Elbaz, David, Estrada-Carpenter, Vicente, Fernandez, Vital, Finkelstein, Keely D., Freundlich, Jonathan, Fujimoto, Seiji, Garcia-Argumanez, Angela, Gardner, Jonathan P., Gawiser, Eric, Gomez-Guijarro, Carlos, Guo, Yuchen, Hamilton, Timothy S., Hathi, Nimish P., Holwerda, Benne W., Hirschmann, Michaela, Huertas-Company, Marc, Hutchison, Taylor A., Iyer, Kartheik G., Jaskot, Anne E., Jha, Saurabh W., Jogee, Shardha, Juneau, Stephanie, Jung, Intae, Kassin, Susan A., Kurczynski, Peter, Larson, Rebecca L., Leung, Gene C. K., Long, Arianna S., Lucas, Ray A., Magnelli, Benjamin, Mantha, Kameswara Bharadwaj, Matharu, Jasleen, McGrath, Elizabeth J., McIntosh, Daniel H., Medrano, Aubrey, Merlin, Emiliano, Mobasher, Bahram, Morales, Alexa M., Newman, Jeffrey A., Nicholls, David C., Pandya, Viraj, Rafelski, Marc, Ronayne, Kaila, Rose, Caitlin, Ryan, Russell E., Santini, Paola, Seille, Lise-Marie, Shah, Ekta A., Shen, Lu, Simons, Raymond C., Snyder, Gregory F., Stanway, Elizabeth R., Straughn, Amber N., Teplitz, Harry, I, Vanderhoof, Brittany N., Vega-Ferrero, Jesus, Wang, Weichen, Weiner, Benjamin J., Willmer, Christopher N. A., Wuyts, Stijn
Lyman-break galaxy (LBG) candidates at z greater than or similar to 10 are rapidly being identified in James Webb Space Telescope (JWST)/NIRCam observations. Due to the (redshifted) break produced by neutral hydrogen absorption of rest-frame UV photons, these sources are expected to drop out in the bluer filters while being well detected in redder filters. However, here we show that dust-enshrouded star-forming galaxies at lower redshifts (z less than or similar to 7) may also mimic the near-infrared (near-IR) colors of z > 10 LBGs, representing potential contaminants in LBG candidate samples. First, we analyze CEERS-DSFG-1, a NIRCam dropout undetected in the F115W and F150W filters but detected at longer wavelengths. Combining the JWST data with (sub)millimeter constraints, including deep NOEMA interferometric observations, we show that this source is a dusty star-forming galaxy (DSFG) at z approximate to 5.1. We also present a tentative 2.6 sigma SCUBA-2 detection at 850 mu m around a recently identified z approximate to 16 LBG candidate in the same field and show that, if the emission is real and associated with this candidate, the available photometry is consistent with a z similar to 5 dusty galaxy with strong nebular emission lines despite its blue near-IR colors. Further observations on this candidate are imperative to mitigate the low confidence of this tentative submillimeter emission and its positional uncertainty. Our analysis shows that robust (sub)millimeter detections of NIRCam dropout galaxies likely imply z similar to 4-6 redshift solutions, where the observed near-IR break would be the result of a strong rest-frame optical Balmer break combined with high dust attenuation and strong nebular line emission, rather than the rest-frame UV Lyman break. This provides evidence that DSFGs may contaminate searches for ultra-high redshift LBG candidates from JWST observations.
Stellar Properties for a Comprehensive Collection of Star-forming Regions in the SDSS APOGEE-2 Survey
(IOP Publishing Ltd, 2023/02/01) Roman-Zuniga, Carlos G., Kounkel, Marina, Hernandez, Jesus, Pena Ramirez, Karla, Lopez-Valdivia, Ricardo, Covey, Kevin R., Stutz, Amelia M., Roman-Lopes, Alexandre, Campbell, Hunter, Khilfeh, Elliott, Tapia, Mauricio, Stringfellow, Guy S., Jose Downes, Juan, Stassun, Keivan G., Minniti, Dante, Bayo, Amelia, Kim, Jinyoung Serena, Suarez, Genaro, Ybarra, Jason E., Fernandez-Trincado, Jose G., Longa-Pena, Penelope, Ramirez-Preciado, Valeria, Serna, Javier, Lane, Richard R., Garcia-Hernandez, D. A., Beaton, Rachael L., Bizyaev, Dmitry, Pan, Kaike
The Sloan Digital Sky Survey IV APOGEE-2 primary science goal was to observe red giant stars throughout the Galaxy to study its dynamics, morphology, and chemical evolution. The APOGEE instrument, a high-resolution 300fiber H-band (1.55-1.71 mu m) spectrograph, is also ideal to study other stellar populations in the Galaxy, among which are a number of star-forming regions and young open clusters. We present the results of the determination of six stellar properties (Teff, log g, [Fe/H], L/L-circle dot, M/M-circle dot, and age) for a sample that is composed of 3360 young stars, of subsolar to supersolar types, in 16 Galactic star formation and young open cluster regions. Those sources were selected by using a clustering method that removes most of the field contamination. Samples were also refined by removing targets affected by various systematic effects of the parameter determination. The final samples are presented in a comprehensive catalog that includes all six estimated parameters. This overview study also includes parameter spatial distribution maps for all regions and Hertzsprung-Russell (log L/L-circle dot vs. T-eff) diagrams. This study serves as a guide for detailed studies on individual regions and paves the way for the future studies on the global properties of stars in the pre-main-sequence phase of stellar evolution using more robust samples.
The Low-redshift Lyman Continuum Survey: Optically Thin and Thick Mg ii Lines as Probes of Lyman Continuum Escape
(IOP Publishing Ltd, 2023/02/01) Xu, Xinfeng, Henry, Alaina, Heckman, Timothy, Chisholm, John, Marques-Chaves, Rui, Leclercq, Floriane, Berg, Danielle A., Jaskot, Anne, Schaerer, Daniel, Worseck, Gabor, Amorin, Ricardo O., Atek, Hakim, Hayes, Matthew, Ji, Zhiyuan, Ostlin, Goran, Saldana-Lopez, Alberto, Thuan, Trinh
The Mg ii lambda lambda 2796, 2803 doublet has been suggested as a useful indirect indicator for the escape of Ly alpha and Lyman continuum (LyC) photons in local star-forming galaxies. However, studies to date have focused on small samples of galaxies with strong Mg ii or strong LyC emission. Here, we present the first study of Mg ii to probe a large dynamic range of galaxy properties, using newly obtained high-signal-to-noise, moderate-resolution spectra of Mg ii, for a sample of 34 galaxies selected from the Low-redshift Lyman Continuum Survey. We show that the galaxies in our sample have Mg ii profiles ranging from strong emission to P-Cygni profiles to pure absorption. We find that there is a significant trend (with a possibility of spurious correlations of similar to 2%) that galaxies that are detected as strong LyC emitters (LCEs) show larger equivalent widths of Mg ii emission, while non-LCEs tend to show evidence of more scattering and absorption features in Mg ii. We then find that Mg ii strongly correlates with Ly alpha in both equivalent width and escape fraction, regardless of whether emission or absorption dominates the Mg ii profiles. Furthermore, we show that, for galaxies that are categorized as Mg ii emitters, one can use the information of Mg ii, metallicity, and dust to estimate the escape fraction of LyC within a factor of similar to 3. These findings confirm that Mg ii lines can be used as a tool for selecting galaxies as LCEs and thus serve as an indirect indicator for the escape of Ly alpha and LyC.
Elemental abundance differences in the massive planet-hosting wide binary HD 196067-68
(OXFORD UNIV PRESS, 2023/02/01) Flores, M., Yana Galarza, J., Miquelarena, P., Saffe, C., Jaque Arancibia, M., Ibanez Bustos, R., V, Jofre, E., Alacoria, J., Gunella, F.
It has been suggested that small chemical anomalies observed in planet-hosting wide binary systems could be due to planet signatures, where the role of the planetary mass is still unknown. We search for a possible planet signature by analysing the T-C trends in the remarkable binary system HD 196067-HD 196068. At the moment, only HD 196067 is known to host a planet that is near the brown dwarf regime. We take advantage of the strong physical similarity between both stars, which is crucial to achieving the highest possible precision in stellar parameters and elemental chemical abundances. This system gives us a unique opportunity to explore whether a possible depletion of refractories in a binary system could be inhibited by the presence of a massive planet. We performed a line-by-line chemical differential study, employing the non-solar-scaled opacities, in order to reach the highest precision in the calculations. After differentially comparing both stars, HD 196067 displays a clear deficiency in refractory elements in the T-C plane, a lower iron content (0.051 dex), and also a lower Li I content (0.14 dex) than its companion. In addition, the differential abundances reveal a T-C trend. These targets represent the first cases of an abundance difference around a binary system hosting a super-Jupiter. Although we explored several scenarios to explain the chemical anomalies, none of them can be entirely ruled out. Additional monitoring of the system as well as studies of larger sample of wide binary systems hosting massive planets are needed to better understand the chemical abundance trend observed in HD 196067-68.
Taking a break: Paused accretion in the symbiotic binary RT Cru
(EDP SCIENCES S A, 2023/02/02) Pujol, A., Luna, G. J. M., Mukai, K., Sokoloski, J. L., Kuin, N. P. M., Walter, F. M., Angeloni, R., Nikolov, Y., de Oliveira, R. Lopes, Nunez, N. E., Arancibia, M. Jaque, Palma, T., Gramajo, L.
Symbiotic binaries sometimes hide their symbiotic nature for significant periods of time. There is mounting observational evidence that, in symbiotics that are powered solely by the accretion of the red giant's wind material onto a white dwarf, without any quasisteady shell burning on the surface of the white dwarf, the characteristic emission lines in the optical spectrum can vanish, leaving the semblance of an isolated red giant spectrum. Here we present compelling evidence that this disappearance of optical emission lines from the spectrum of RT Cru in 2019 was due to a decrease in the accretion rate, which we derived by modeling the X-ray spectrum. This drop in accretion rate leads to a lower flux of ionizing photons and thus to faint or absent photoionization emission lines in the optical spectrum. We observed the white dwarf symbiotic RT Cru with XMM-Newton and Swift in X-rays and UV and collected ground-based optical spectra and photometry obtained over the last 33 yr. This long-term coverage shows that, during most of the year 2019, the accretion rate onto the white dwarf was so low,. M = (3 :2 +/- 0 :06) x 10(-1)1 M fi yr(-1) (d /2.52 kpc)(2), that the historically detected hard X-ray emission almost vanished, the UV flux faded by roughly 5 mag, the U, B, and V flickering amplitude decreased, and the Balmer lines virtually disappeared from 2019 January through March. Long-lasting low-accretion episodes such as the one reported here may hamper the chances of RT Cru experiencing a nova-type outburst despite the high mass of the accreting white dwarf.
The resolved chemical composition of the starburst dwarf galaxy CGCG007-025: direct method versus photoionization model fitting
(OXFORD UNIV PRESS, 2023/02/15) Fernandez, V, Amorin, R., Sanchez-Janssen, R., del Valle-Espinosa, M. G., Papaderos, P.
This work focuses on the gas chemical composition of CGCG007-025. This compact dwarf is undergoing a galaxy wide star-forming burst, whose spatial behaviour has been observed by VLT/MUSE. We present a new line measurement library to treat almost 7800 voxels. The direct method chemical analysis is limited to 484 voxels with good detection of the [S III]6312 angstrom temperature diagnostic line. The recombination fluxes are corrected for stellar absorption via a population synthesis. Additionally, we discuss a new algorithm to fit photoionization models via neural networks. The eight ionic abundances analysed show a spatial normal distribution with a sigma similar to 0. 1 dex, where only half this value can be explained by the uncertainty in the measurements. The oxygen abundance distribution is 12 + log(O/H) = 7.88 +/- 0.11. The T-e[S III] and ne[S II] are also normally distributed. However, in the central and brightest region, the ne[S II] is almost thrice the mean galaxy value. This is also reflected in the extinction measurements. The ionization parameter has a distribution of log(U) = -2.52(0.019)(0.17). The parameter spatial behaviour agrees with the S2+/S+ map. Finally, the discrepancies between the direct method and the photoionization model fitting are discussed. In the latter technique, we find that mixing lines with uneven uncertainty magnitudes can impact the accuracy of the results. In these fittings, we recommend overestimating the minimum flux uncertainty one order below the maximum line flux uncertainty. This provides a better match with the direct method.
The chemical characterization of halo substructure in the Milky Way based on APOGEE
(OXFORD UNIV PRESS, 2023/02/22) Horta, Danny, Schiavon, Ricardo P., Mackereth, J. Ted, Weinberg, David H., Hasselquist, Sten, Feuillet, Diane, O'Connell, Robert W., Anguiano, Borja, Allende-Prieto, Carlos, Beaton, Rachael L., Bizyaev, Dmitry, Cunha, Katia, Geisler, Doug, Garcia-Hernandez, D. A., Holtzman, Jon, Joensson, Henrik, Lane, Richard R., Majewski, Steve R., Meszaros, Szabolcs, Minniti, Dante, Nitschelm, Christian, Shetrone, Matthew, Smith, Verne V., Zasowski, Gail
Galactic haloes in a ?-CDM universe are predicted to host today a swarm of debris resulting from cannibalized dwarf galaxies. The chemodynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I'itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ, (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way, (iii) the chemistry of Arjuna, LMS-1, and I'itoi is indistinguishable from that of GES, suggesting a possible common origin, (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion, (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures.
The Physical Conditions of Emission-line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations
(IOP Publishing Ltd, 2023/03/01) Trump, Jonathan R., Haro, Pablo Arrabal, Simons, Raymond C., Backhaus, Bren E., Amorin, Ricardo O., Dickinson, Mark, Fernandez, Vital, Papovich, Casey, Nicholls, David C., Kewley, Lisa J., Brunker, Samantha W., Salzer, John J., Wilkins, Stephen M., Almaini, Omar, Bagley, Micaela B., Berg, Danielle A., Bhatawdekar, Rachana, Bisigello, Laura, Buat, Veronique, Burgarella, Denis, Calabro, Antonello, Casey, Caitlin M., Ciesla, Laure, Cleri, Nikko J., Cole, Justin W., Cooper, M. C., Cooray, Asantha R., Costantin, Luca, Croton, Darren, Ferguson, Henry C., Finkelstein, Steven L., Fujimoto, Seiji, Gardner, Jonathan P., Gawiser, Eric, Giavalisco, Mauro, Grazian, Andrea, Grogin, Norman A., Hathi, Nimish P., Hirschmann, Michaela, Holwerda, Benne W., Huertas-Company, Marc, Hutchison, Taylor A., Jogee, Shardha, Juneau, Stephanie, Jung, Intae, Kartaltepe, Jeyhan S., Kirkpatrick, Allison, Kocevski, Dale D., Koekemoer, Anton M., Lotz, Jennifer M., Lucas, Ray A., Magnelli, Benjamin, Matharu, Jasleen, Perez-Gonzalez, Pablo G., Pirzkal, Nor, Rafelski, Marc, Rose, Caitlin, Seille, Lise-Marie, Somerville, Rachel S., Straughn, Amber N., Tacchella, Sandro, Vanderhoof, Brittany N., Weiner, Benjamin J., Wuyts, Stijn, Aaron Yung, L. Y., Zavala, Jorge A.
We present rest-frame optical emission-line flux ratio measurements for five z > 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliable relative flux calibration of emission lines that are closely separated in wavelength, despite the uncertain absolute spectrophotometry of the current version of the reductions. Compared to z similar to 3 galaxies in the literature, the z > 5 galaxies have similar [O iii]lambda 5008/H beta ratios, similar [O iii]lambda 4364/H gamma ratios, and higher (similar to 0.5 dex) [Ne III]lambda 3870/[O II]lambda 3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [Ne III]lambda 3870/[O II]lambda 3728, [O iii]lambda 4364/H gamma, and [O iii]lambda 5008/H beta emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( log(Q)?8-9 , units of cm s(-1)), low metallicity (Z/Z (?) ? 0.2), and very high pressure ( log(P/k)?8-9, units of cm(-3)). The combination of [O iii]lambda 4364/H gamma and [O iii]lambda(4960 + 5008)/H beta line ratios indicate very high electron temperatures of 4.1 < log(T-e/K) < 4.4, further implying metallicities of Z/Z(?)?0.2 with the application of low-redshift calibrations for T-e -based metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.
CEERS Key Paper. III. The Diversity of Galaxy Structure and Morphology at z=3-9 with JWST
(IOP Publishing Ltd, 2023/03/01) Kartaltepe, Jeyhan S., Rose, Caitlin, Vanderhoof, Brittany N., McGrath, Elizabeth J., Costantin, Luca, Cox, Isabella G., Yung, L. Y. Aaron, Kocevski, Dale D., Wuyts, Stijn, Ferguson, Henry C., Bagley, Micaela B., Finkelstein, Steven L., Amorin, Ricardo O., Andrews, Brett H., Haro, Pablo Arrabal, Backhaus, Bren E., Behroozi, Peter, Bisigello, Laura, Calabro, Antonello, Casey, Caitlin M., Coogan, Rosemary T., Cooper, M. C., Croton, Darren, de la Vega, Alexander, Dickinson, Mark, Fontana, Adriano, Franco, Maximilien, Grazian, Andrea, Grogin, Norman A., Hathi, Nimish P., Holwerda, Benne W., Huertas-Company, Marc, Iyer, Kartheik G., Jogee, Shardha, Jung, Intae, Kewley, Lisa J., Kirkpatrick, Allison, Koekemoer, Anton M., Liu, James, Lotz, Jennifer M., Lucas, Ray A., Newman, Jeffrey A., Pacifici, Camilla, Pandya, Viraj, Papovich, Casey, Pentericci, Laura, Perez-Gonzalez, Pablo G., Petersen, Jayse, Pirzkal, Nor, Rafelski, Marc, Ravindranath, Swara, Simons, Raymond C., Snyder, Gregory F., Somerville, Rachel S., Stanway, Elizabeth R., Straughn, Amber N., Tacchella, Sandro, Trump, Jonathan R., Vega-Ferrero, Jesus, Wilkins, Stephen M., Yang, Guang, Zavala, Jorge A.
We present a comprehensive analysis of the evolution of the morphological and structural properties of a large sample of galaxies at z = 3-9 using early James Webb Space Telescope (JWST) CEERS NIRCam observations. Our sample consists of 850 galaxies at z > 3 detected in both Hubble Space Telescope (HST)/WFC3 and CEERS JWST/NIRCam images, enabling a comparison of HST and JWST morphologies. We conduct a set of visual classifications, with each galaxy in the sample classified three times. We also measure quantitative morphologies across all NIRCam filters. We find that galaxies at z > 3 have a wide diversity of morphologies. Galaxies with disks make up 60% of galaxies at z = 3, and this fraction drops to similar to 30% at z = 6-9, while galaxies with spheroids make up similar to 30%-40% across the redshift range, and pure spheroids with no evidence for disks or irregular features make up similar to 20%. The fraction of galaxies with irregular features is roughly constant at all redshifts (similar to 40%-50%), while those that are purely irregular increases from similar to 12% to similar to 20% at z > 4.5. We note that these are apparent fractions, as many observational effects impact the visibility of morphological features at high redshift. On average, Spheroid-only galaxies have a higher Sersic index, smaller size, and higher axis ratio than disk or irregular galaxies. Across all redshifts, smaller spheroid and disk galaxies tend to be rounder. Overall, these trends suggest that galaxies with established disks and spheroids exist across the full redshift range of this study, and further work with large samples at higher redshift is needed to quantify when these features first formed.
Assessing model-based carbon and oxygen abundance derivation from ultraviolet emission lines in AGNs
(OXFORD UNIV PRESS, 2023/03/02) Perez-Montero, E., Amorin, R., Perez-Diaz, B., Vilchez, J. M., Garcia-Benito, R.
We present an adapted version of the code HII-CHI-mistry-UV to derive chemical abundances from emission lines in the ultraviolet, for use in narrow line regions (NLR) of active galactic nuclei (AGN). We evaluate different ultraviolet emission line ratios and how different assumptions about the models, including the presence of dust grains, the shape of the incident spectral energy distribution, or the thickness of the gas envelope around the central source, may affect the final estimates as a function of the set of emission lines used. We compare our results with other published recipes for deriving abundances using the same emission lines and show that deriving the carbon-to-oxygen abundance ratio using C iii] lambda 1909 angstrom and O iii] lambda 1665 angstrom emission lines is a robust indicator of the metal content in AGN that is nearly independent of the model assumptions, similar to the case of star-forming regions. Moreover, we show that a prior determination of C/O allows for a much more precise determination of the total oxygen abundance using carbon UV lines, as opposed to assuming an arbitrary relationship between O/H and C/O, which can lead to non-negligible discrepancies.
A trail of the invisible: blue globular clusters trace the radial density distribution of the dark matter - case study of NGC 4278
(OXFORD UNIV PRESS, 2023/03/31) Kluge, Matthias, Remus, Rhea-Silvia, Babyk, Iurii, V, Forbes, Duncan A., Dolfi, Arianna
We present new, deep optical observations of the early-type galaxy NGC 4278, which is located in a small loose group. We find that the galaxy lacks fine substructure, that is, it appears relaxed, out to a radius of similar to 70 kpc. Our g- and i-band surface brightness profiles are uniform down to our deepest levels of similar to 28 mag arcsec(-2). This spans an extremely large radial range of more than 14 half-mass radii. Combined with archival globular cluster (GC) number density maps and a new analysis of the total mass distribution obtained from archival Chandra X-ray data, we find that the red GC subpopulation traces well the stellar mass density profile from 2.4 out to even 14 half-mass radii, while the blue GC subpopulation traces the total mass density profile of the galaxy over a large radial range. Our results reinforce the scenario that red GCs form mostly in situ along with the stellar component of the galaxy, while the blue GCs are more closely aligned with the total mass distribution in the halo and were accreted along with halo matter. We conclude that for galaxies where the X-ray emission from the hot halo is too faint to be properly observable and as such is not available to measure the dark matter profile, the blue GC population can be used to trace this dark matter component out to large radii.