Browsing by Author "Sharon, K. "
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- ItemA multi-wavelength mass analysis of RCS2 J232727.6-020437, A similar to 3 x 10(15) M-circle dot galaxy cluster AT z=0.7(2015) Sharon, K.; Gladders, M. D.; Marrone, D. P.; Hoekstra, H.; Rasia, E.; Barrientos, Luis Felipe
- ItemMolecular gas budget and characterization of intermediate-mass star-forming galaxies at z ≈ 2–3(2021) Solimano, M. ; González-López, J. ; Barrientos, L. F. ; Aravena, M. ; López, S. ; Tejos, N. ; Sharon, K. ; Dahle, H. ; Bayliss, M. ; Ledoux, C. ; Rigby, J. R. ; Gladders, M.Star-forming galaxies (SFGs) with stellar masses below 10(10) M-circle dot make up the bulk of the galaxy population at z > 2. The properties of the cold gas in these galaxies can only be probed in very deep observations or by targeting strongly lensed galaxies. Here we report the results of a pilot survey using the Atacama Compact Array of molecular gas in the most strongly magnified galaxies selected as giant arcs in optical data. The selection in rest-frame ultraviolet (UV) wavelengths ensures that sources are regular SFGs, without a priori indications of intense dusty starburst activity. We conducted Band 4 and Band 7 observations to detect mid-J CO, [C I] and thermal continuum as molecular gas tracers from four strongly lensed systems at z approximate to 2-3: our targets are SGAS J1226651.3+215220 (A and B), SGAS J003341.5+024217 and the Sunburst Arc. The measured molecular mass was then projected onto the source plane with detailed lens models developed from high resolution Hubble Space Telescope observations. Multiwavelength photometry was then used to obtain the intrinsic stellar mass and star formation rate via spectral energy distribution modeling. In only one of the sources are the three tracers robustly detected, while in the others they are either undetected or detected in continuum only. The implied molecular gass masses range from 4 x 10(9) M-circle dot in the detected source to an upper limit of less than or similar to 10(9) M-circle dot in the most magnified source. The inferred gas fraction and gas depletion timescale are found to lie approximately 0.5-1.0 dex below the established scaling relations based on previous studies of unlensed massive galaxies, but in relative agreement with existing literature about UV-bright lensed galaxies at these high redshifts. Our results indicate that the cold gas content of intermediate to low mass galaxies should not be extrapolated from the trends seen in more massive high-z galaxies. The apparent gas deficit is robust against biases in the stellar mass or star formation rate. However, we find that in this mass-metallicity range, the molecular gas mass measurements are severely limited by uncertainties in the current tracer-to-gas calibrations.
- ItemMolecular gas budget of strongly magnified low-mass star-forming galaxies at cosmic noon(2024) Catán Valenzuela, Victoria Sofia; González López, Jorge; Solimano Gambardella, Manuel Antonio; Barrientos, Luis Felipe; Afruni, A.; Aravena, M.; Bayliss, M.; Hernández, J. A.; Ledoux, C.; Mahler, G.; Sharon, K.; Tejos, N.Aims. The aim of this study is to investigate the molecular gas content of strongly magnified low-mass star-forming galaxies (SFGs) around the cosmic noon period (z ∼ 2) through observations of carbon monoxide (CO) emission lines and dust continuum emission, both of which serve as tracers of molecular gas (H2). Methods. We observed 12 strongly lensed arcs with the Atacama Compact Array (ACA) to detect CO mid-J rotational transitions and dust continuum. Thanks to the strong lensing, we were able to probe the previously understudied low-mass regime. With a compiled set of observations, we recalibrated empirical relations between star formation rate density (ΣSFR) and the CO line ratios. We derived galaxy properties using spectral energy distribution fitting (SED). We also performed galaxy stacking to combine faint signals. In all cases, molecular gas masses were estimated using both tracers. Results. We detected CO emission in 3 of the 12 arcs and dust continuum emission in another 3. The obtained H2 masses indicate that most of these galaxies (M* < 1010.7 M⊙) have lower molecular gas fractions and shorter depletion times compared to expectations from established scaling relations at these redshifts. We explored several possible explanations for this gas deficit, including uncertainties in mass estimates, effects of low-metallicity environments, larger atomic gas reservoirs in low-mass systems, and the possibility that these represent low-mass analogs of main sequence starburst (MS SBs) galaxies that are undergoing sustained star formation due to gas compaction despite low overall gas fractions. Conclusions. We conclude that these mass and metallicity regimes present a molecular gas deficit. Our results suggest that this deficit is likely due to a significant amount of atomic gas, which our stacking indicates is about 91% of the total gas. However, this estimation might be an upper limit, as the possibility remains that our galaxies contain CO-dark gas.
- ItemOrientation effects on cool gas absorption from gravitational-arc tomography of a z=0.77 disc galaxy(2022) Fernandez-Figueroa, A.; Lopez, S.; Tejos, N.; Berg, T. A. M.; Ledoux, C.; Noterdaeme, P.; Afruni, A.; Barrientos, L. F.; Gonzalez-Lopez, J.; Hamel, M.; Johnston, E. J.; Katsianis, A.; Sharon, K.; Solimano, M.We use spatially resolved spectroscopy of a distant giant gravitational arc to test orientation effects on Mg ii absorption equivalent width (EW) and covering fraction () in the circumgalactic medium of a foreground star-forming galaxy (G1) at z similar to 0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles alpha between 30 degrees and 90 degrees (minor axis). We find an EW-D anticorrelation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and with alpha, revealing a non-isotropic gas distribution. In line with our previous results on Mg ii kinematics suggesting the presence of outflows in G1, at minimum a simple 3D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and alpha values probed by the arc cannot confirm the presence of a disc, but the data highly disfavour a disc alone. Our results support the interpretation that the EW-alpha correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.
- ItemSlicing the cool circumgalactic medium along the major axis of a star-forming galaxy at z=0.7(2020) Lopez, S.; Tejos, N.; Barrientos, Luis Felipe; Ledoux, C.; Sharon, K.; Katsianis, A.; Florian, M.K.; Rivera-Thorsen, E.; Bayliss, M.B.; Dahle, H.; Fernandez-Figueroa, A.; Gladders, M.D.; Gronke, M.; Hamel, M.; Pessa, I.; Rigby, J.R.
- ItemSource-plane reconstruction of the bright lensed galaxy RCSGA 032727-132609(2012) Sharon, K.; Barrientos, Luis Felipe
- ItemSpatially Resolved Outflows in a Seyfert Galaxy at z = 2.39(2019) Fischer, Travis C.; Rigby, J. R.; Mahler, G.; Gladders, M.; Sharon, K.; Florian, M.; Kraemer, S.; Bayliss, M.; Dahle, H.; Barrientos, L. Felipe; Lopez, S.; Tejos, N.; Johnson, T.; Wuyts, E.We present the first spatially resolved analysis of rest-frame optical and UV imaging and spectroscopy for a lensed galaxy at z = 2.39 hosting a Seyfert active galactic nucleus (AGN). Proximity to a natural guide star has enabled observations with high signal-to-noise ratio using Very Large Telescope SINFONI + adaptive optics (AO) of rest-frame optical diagnostic emission lines, which exhibit an underlying broad component with full width at half maximum similar to 700 km s(-1) in both the Balmer and forbidden lines. Measured line ratios place the outflow robustly in the region of the ionization diagnostic diagrams associated with AGNs. This unique opportunity-combining gravitational lensing, AO guiding, redshift, and AGN activity-allows for a magnified view of two main tracers of the physical conditions and structure of the interstellar medium in a star-forming galaxy hosting a weak AGN at Cosmic Noon. By analyzing the spatial extent and morphology of the Ly alpha and dust-corrected H alpha emission, disentangling the effects of star formation and AGN ionization on each tracer, and comparing the AGN-induced mass outflow rate to the host star formation rate, we find that the AGN does not significantly impact the star formation within its host galaxy.
- ItemTelltale signs of metal recycling in the circumgalactic medium of a z 0.77 galaxy(2021) Tejos, N.; López, S.; Ledoux, C.; Fernández-Figueroa, A.; Rivas, N.; Sharon, K.; Johnston, E. J.; Florian, M. K.; D'Ago, G.; Katsianis, A.; Barrientos, F.; Berg, T.; Corro-Guerra, F.; Hamel, M.; Moya-Sierralta, C.; Poudel, S.; Rigby, J. R.; Solimano, M.We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy ('G1') at z approximate to 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy, we obtain partially resolved kinematics of Mg II in absorption and [O II] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus four positions in front of it. The transverse positions cover G1's minor and major axes at impact parameters of approximate to 10-30 and approximate to 60kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg II) and the interstellar medium (traced by [O II]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg II velocity dispersion (sigma approximate to 30-100 km s(-1), depending on position) is of the same order as the modelled galaxy rotational velocity (v(rot) approximate to 80 km s(-1)), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z similar to 1 CGM.