adsabs/AstroCLIMB huggingface dataset:
Paper: Pearls on a String: Dark and Bright Galaxies on a Strikingly Straight and Narrow Filament
Authors: M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc'h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud, M. A. Zwaan
Figure caption: The r-band CFHT image, with the squares marking the positions of the H I sources detected within the JVLA HPBW (listed in Table 2). G3–G6 are marked with red squares. The HPBW of JVLA is marked with a white dashed circle.
Paper: Discovery of Metal-poor and Distant Pre–Main Sequence Candidates in WLM with JWST
Authors: Venu M. Kalari, Ricardo Salinas, Morten Andersen, Guido De Marchi, Monica Rubio, Jorick S. Vink, Hans Zinnecker
Figure caption: (F090W–F150W) vs. F090W CMD of the whole JWST field of view (gray dots) and the central cluster (blue crosses). Shown are the 1, 3, 8, and 10 Myr A. Dotter (2016) isochrones. The stellar masses correspond to main-sequence stars at the distance and extinction adopted. The PMS candidates selected using the two-color diagrams are shown as red circles. The extinction vector corresponds to the adopted foreground and cluster extinction value (see text).
Paper: Discovery of Metal-poor and Distant Pre–Main Sequence Candidates in WLM with JWST
Authors: Venu M. Kalari, Ricardo Salinas, Morten Andersen, Guido De Marchi, Monica Rubio, Jorick S. Vink, Hans Zinnecker
Figure caption: (F090W–F150W) vs. (F150W–F250M) (left) and (F090W–F150W) vs. (F150W–F430M) (right) two-color diagrams of WLM. The main-sequence color locus from A. Dotter (2016) is given by the dotted line. Blue crosses represent all sources falling within the central cluster, while red circles give the sources marked as having infrared excesses in both F250M and F430M filters and are the PMS candidates. The stellar masses correspond to main-sequence stars at the distance and extinction adopted. Photometric uncertainties are only given for PMS candidates.
Paper: Stellar Streams Reveal the Mass Loss of Globular Clusters
Authors: Yingtian Chen, Hui Li, Oleg Y. Gnedin
Figure caption: Mass-loss rate of 12 GCs against MGC (first panel), Ω (second panel), rh (third panel), and best-fit mass-loss rate ﹩{\dot{M}}_{{\rm{fit}}}﹩ (fourth panel). The uncertainty of ﹩\dot{M}﹩ (from Poisson errors and the MF slope) is plotted as vertical error bars. Horizontal error bars in the fourth panel represent the uncertainty of the best-fit power-law relation (Equations (10) and (12)). Gray shaded regions in the first three panels show the best-fit mass-loss rate and the associated uncertainty, with the other two GC properties set to the reference values: MGC = 2 × 105 M⊙, Ω = 30 Gyr−1, and rh = 5 pc. Magenta regions show the (a, b, c) = (1/3, 1, 0) model from M. Gieles & O. Y. Gnedin (2023) with ﹩|{\dot{M}}_{{\rm{ref}}}|=30-45\,{M}_{\odot }\,{{\rm{Myr}}}^{-1}﹩. Gray lines in the first panel indicate the expected lifetime if GCs continue to dissolve at the current rates. The gray line in the fourth panel indicates the one-to-one agreement.
Paper: Stellar Streams Reveal the Mass Loss of Globular Clusters
Authors: Yingtian Chen, Hui Li, Oleg Y. Gnedin
Figure caption: Gaia observations of 12 GC streams (black open symbols) and their corresponding mock streams (colored solid symbols). Stream segments are represented as gray regions. The widths of these regions stand for ±3σdetect. The mock stream particles are color coded by their lookback release time, as indicated by the color bar. The progenitor clusters are shown as star symbols.
Paper: NGDEEP: The Star Formation and Ionization Properties of Galaxies at 1.7 < z < 3.4
Authors: Lu Shen, Casey Papovich, Jasleen Matharu, Nor Pirzkal, Weida Hu, Danielle A. Berg, Micaela B. Bagley, Bren E. Backhaus, Nikko J. Cleri, Mark Dickinson, Steven L. Finkelstein, Nimish P. Hathi, Marc Huertas-Company, Taylor A. Hutchison, Mauro Giavalisco, Norman A. Grogin, Anne E. Jaskot, Intae Jung, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Jennifer M. Lotz, Pablo G. Pérez-González, Barry Rothberg, Raymond C. Simons, Brittany N. Vanderhoof, L. Y. Aaron Yung
Figure caption: Top panels: comparison of calibrated E(B − V) using a uniform star-to-gas attenuation ratio of 0.44 (filled green squares) or 1 (filled purple diamonds) or an SFR-dependent star-to-gas attenuation ratio (blue dots) to E(B − V)gas from the Balmer decrement as a function of stellar mass (left) and SFR (right). Bottom panels: comparison of O32 using calibrated E(B − V) based on E(B − V)star and E(B − V)gas from the Balmer decrement as a function of stellar mass and SFR. The median values are shown as larger markers. The median values using an SFR-dependent star-to-gas attenuation ratio (filled blue circles) are shifted to the right for clarity.
Paper: Rates of Stellar Tidal Disruption Events around Intermediate-mass Black Holes
Authors: Janet N. Y. Chang, Lixin Dai, Hugo Pfister, Rudrani Kar Chowdhury, Priyamvada Natarajan
Figure caption: The TDE rate of an IMBH host galaxy NGC 1042 calculated using MBH,best (left) and ﹩{M}_{{\rm{BH}},{\rm{\max }}}﹩ (right). The top row shows the cumulative TDE rate fraction as a function of E. The blue vertical dashed line indicates q = 1, which is the boundary separating the pinhole regime (left side) and diffusive regime (right side). The bottom row shows contour plots illustrating how the differential TDE rate ﹩d{{\rm{\Gamma }}}^{2}/dEd\,\mathrm{ln}\beta ﹩ depends on β (penetration parameter) and E (orbital specific energy).
Paper: Rates of Stellar Tidal Disruption Events around Intermediate-mass Black Holes
Authors: Janet N. Y. Chang, Lixin Dai, Hugo Pfister, Rudrani Kar Chowdhury, Priyamvada Natarajan
Figure caption: The gradient of Γ(MBH) calculated at the observed MBH,obs plotted against the Sérsic inner slope p (of the innermost stellar component) for each galaxy. The circle symbol style and color are consistent with Figure 1(a). The solid blue line shows the linear fit, and the dashed blue line marks where ﹩d\mathrm{log}{\rm{\Gamma }}/d\mathrm{log}\,{M}_{{\rm{BH}}}=0﹩. The curves cross at p ∼ 0.62.
Paper: Rates of Stellar Tidal Disruption Events around Intermediate-mass Black Holes
Authors: Janet N. Y. Chang, Lixin Dai, Hugo Pfister, Rudrani Kar Chowdhury, Priyamvada Natarajan
Figure caption: A schematic of two types of galaxies and the TDEs occurring in these galaxies. Left: a low-mass galaxy with an IMBH residing at the galactic nucleus. Such a galaxy typically has not only a stellar bulge but also denser NSC components, which boost TDE rates. A TDE can occur around the central IMBH (i.e., TDE IMBH-GN). Right: a massive galaxy with an SMBH at the galactic nucleus. The massive galaxy is surrounded by GCs, some of which can host IMBHs. TDEs can occur around the SMBH at the center of the main galaxy (i.e., TDE SMBH), or around the IMBHs that are off nuclei (i.e., TDE IMBH-ON).
Paper: Rates of Stellar Tidal Disruption Events around Intermediate-mass Black Holes
Authors: Janet N. Y. Chang, Lixin Dai, Hugo Pfister, Rudrani Kar Chowdhury, Priyamvada Natarajan
Figure caption: The ratio between the BH influence radius ﹩{r}_{{\rm{\inf }}}﹩ and the effective radius Reff (of the innermost stellar component) of a galaxy plotted against MBH for each galaxy. The symbol style and color are consistent with Figure 1(d).
Paper: Rates of Stellar Tidal Disruption Events around Intermediate-mass Black Holes
Authors: Janet N. Y. Chang, Lixin Dai, Hugo Pfister, Rudrani Kar Chowdhury, Priyamvada Natarajan
Figure caption: TDE rate Γ vs. stellar density at the BH influence radius ﹩{\rho }_{{\rm{\inf }}}﹩ (left), and the stellar density at 1 pc away from the galactic center ρ1pc (right). The symbol styles and colors are consistent with Figure 1(d).
Paper: Time-resolved Hubble Space Telescope UV Observations of an X-Ray Quasiperiodic Eruption Source
Authors: T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham, R. Arcodia
Figure caption: Relevant length scales and parameter inferences. The top panel shows probability density functions of the various length scales in the system, including the black hole ISCO radius (blue), the stellar tidal radius (orange), the orbiter radius (green), and the disk outer radius (red). Dotted lines show the posteriors for the full spin range, while the solid lines show the results for positive spin. The bottom left panel shows the posterior distribution of the inferred black hole mass. The bottom right panel illustrates that the (MS) stellar mass cannot exceed 1 M⊙, as this would lead to a full tidal disruption (see text for more details).
Paper: Time-resolved Hubble Space Telescope UV Observations of an X-Ray Quasiperiodic Eruption Source
Authors: T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham, R. Arcodia
Figure caption: Constraints on the eruption SED. The top left panel shows the X-ray spectra in the quiescent (black/gray), rise (blue), and peak (red) phases. The decay phase is omitted for clarity. Shaded regions illustrate the 68% CI of the posterior distributions. Dashed lines show the median values of the posteriors for the thermal/bbody component. The top right panel illustrates the 68% confidence contours of the posteriors of the thermal component only; a 3σ upper limit is shown in the FUV (i.e., this assumes that the FUV emission is produced entirely by the quiescent emission). The bottom panels are identical to the top panels but show the more detailed calculations from I. Vurm et al. (2024) (see the text for details).
Paper: Time-resolved Hubble Space Telescope UV Observations of an X-Ray Quasiperiodic Eruption Source
Authors: T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham, R. Arcodia
Figure caption: Quiescent SED modeling results. The observed (top left) and extinction-corrected, rest-frame (top right) SEDs are shown (black: X-ray data, orange: FUV data). The shaded regions show the best-fit model, with the gray band indicating the region containing 68% of the model posteriors. Also shown are upper limits for young stars (green: 10 Myr, red: 100 Myr) in an NSC, using simple stellar populations models (see Section 2.4 for details), assuming the maximum star formation rate surface density in the SDSS MaNGA survey. In both panels, the data is unfolded to the median of the posterior. Marginalized posterior distributions are shown for all free parameters in the bottom row, where solid lines indicate the median and dashed lines the 68% credible interval.
Paper: Time-resolved Hubble Space Telescope UV Observations of an X-Ray Quasiperiodic Eruption Source
Authors: T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham, R. Arcodia
Figure caption: Full marginalized posteriors for the diskSED fits. The left panel shows the quiescent component fit, while the right panel shows the eruption component phase-resolved fits. The color coding is the same as Figure 3. In the 2D histograms, the contours show 68% and 99% of the probability distributions.
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Rest-frame UV luminosity per unit SFR ηUV for a top-hat star formation history within a timescale tSF = 100 Myr. As in Figure  1, the left and right panels show the results for Salpeter and top-heavy IMFs, with α = 2.35 and 1, respectively. While the mass range of nonrotating stars is fixed as m⋆ ∈ [1.7, 300] M⊙, we plot ηUV as a function of ﹩{m}_{\star ,{\rm{\min }}}^{{\rm{CHE}}}﹩ for fCHE ∈ [0, 1], where fCHE increases for lighter colors (from bottom to top). The dotted curve with error bars shows the maximum ηUV in the alternative population model with a fixed overall IMF (corresponding to the maximum CHE mass fraction ﹩{f}_{{\rm{CHE}}}^{{\rm{\max }}}﹩), which is estimated to be in between ﹩{\eta }_{{\rm{UV}}}({f}_{{\rm{CHE}}}={f}_{{\rm{CHE}}}^{{\rm{\max }}})﹩ and ﹩{f}_{{\rm{CHE}}}^{{\rm{\max }}}{\eta }_{{\rm{UV}}}({f}_{{\rm{CHE}}}=1)﹩. We also show the reference value ηUV ≃ 8.70  ×  1027 from P. Madau & M. Dickinson (2014) with the dashed line, which is very close to our result for fCHE = 0 given α = 2.35. The shaded regions show the results for Pop III stars with extremely top-heavy IMFs from K. Inayoshi et al. (2022).
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Constraints on UV emission efficiency and variability from JWST data. The colored curves show the values of ϵ0ηUV and σUV required to reproduce ﹩\mathrm{log}({\rm{\Phi }}({M}_{{\rm{UV}}}=\,-20.5)\,[{{\rm{mag}}}^{-1}\,{{\rm{cMpc}}}^{-3}])=-5﹩ and  −5.3 at z = 10 (solid) and 12 (dashed–dotted) based on spectroscopy and ﹩\mathrm{log}({\rm{\Phi }}({M}_{{\rm{UV}}}=-20.5)\,[{{\rm{mag}}}^{-1}\,{{\rm{cMpc}}}^{-3}])=-4.5﹩,  −5, and  −5.2 at z = 10 (dashed), 12 (dotted), and 16 (long dashed) from photometry. Three representative cases of different ηUV with fixed ϵ0 = 0.1 are shown by the thick vertical lines: the top-heavy models with no CHE (fCHE = 0, dashed) and optimal CHE (fCHE = 1, ﹩{m}_{\star ,\min }^{\mathrm{CHE}}=3\,{M}_{\odot }﹩, dashed–dotted) and the Salpeter model with optimal CHE (fCHE = 1, ﹩{m}_{\star ,\min }^{\mathrm{CHE}}=4\,{M}_{\odot }﹩, dotted). The thin solid and dashed horizontal lines show the minimum and maximum UV variability estimated by X. Shen et al. (2023).
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Rest-frame UV light curve: evolution of UV luminosity normalized by the total stellar mass for a single-age stellar population. The left (right) panel shows the results for a Salpeter (top-heavy) IMF, ﹩dN/d{m}_{\star }\propto {m}_{\star }^{-\alpha }﹩, with a slope α = 2.35 (1) and a mass range m⋆ ∈ [1.7, 300] M⊙ for both nonrotating and CHE stars. The mass fraction of CHE stars fCHE is varied between 0 and 1, with lighter colors denoting larger fCHE.
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: UVLF for select degenerate models that meet the photometric constraints from JWST at z = 12, i.e., ﹩\mathrm{log}({\rm{\Phi }}({M}_{{\rm{UV}}}=-20.5)\,[{{\rm{mag}}}^{-1}\,{{\rm{cMpc}}}^{-3}])=-5﹩. These include the reference case with ηUV ≃ 8.70  ×  1027 (solid) and the three representative models with enhanced UV emission from CHE and/or a top-heavy IMF considered in Figure 3. For comparison, the observational data for z ∼ 11−13 (R. P. Naidu et al. 2022; R. J. Bouwens et al. 2023; C. T. Donnan et al. 2023, 2024; Y. Harikane et al. 2023; P. G. Pérez-González et al. 2023; N. J. Adams et al. 2024; C. M. Casey et al. 2024; S. L. Finkelstein et al. 2024; D. J. McLeod et al. 2024; B. Robertson et al. 2024; C. J. Willott et al. 2024) are shown using CORECON (E. Garaldi 2023), among which the data points with arrows are upper limits. We also plot the results for constant SFE ϵ⋆ = 0.03, 0.1, 0.3, and 1 (from bottom to top) without UV variability as the thick solid lines.
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Same as Figure 2 but for a star formation timescale tSF = 1000 Myr.
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Same as Figure 2 but for a star formation timescale tSF = 10 Myr.
Paper: Pearls on a String: Dark and Bright Galaxies on a Strikingly Straight and Narrow Filament
Authors: M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc'h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud, M. A. Zwaan
Figure caption: H I 21 cm emission spectra of detected H I sources listed in Table 2. All the spectra are extracted from the cube with 35 km s−1 channels (see Table 3). The blue-dotted line marks the rms noise level. The best-fitted Gaussian functions to the spectra are shown with red-dotted–dashed lines. For G3 with a double-horn-like H I spectrum, we also fitted a busy-function (T. Westmeier et al. 2014) to the H I 21 cm emission line, presented by the purple-dotted–dashed line. This results to a Δv0.037 of −5 km s−1, and an FWHMHI of 317 km s−1, consistent with those obtained by fitting a Gaussian. The H I 21 cm emission line from S10 seemed to be like a double-horn emission line; but after carefully checking the H I 21 cm emission in individual channels, we concluded the emission to originate from at least two individual components. We therefore fitted a double-Gaussian function to the H I spectrum of this source to have a better understanding of its velocity spread. This is presented with the purple-dotted–dashed line.
Paper: Pearls on a String: Dark and Bright Galaxies on a Strikingly Straight and Narrow Filament
Authors: M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc'h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud, M. A. Zwaan
Figure caption: H I 21 cm emission spectra of S1–S12 listed in Table 2, extracted from the cube with 50 km s−1 channels (see Table 3), for comparison with the spectra presented in Figure 6. The blue-dotted line marks the rms noise level.
Paper: Pearls on a String: Dark and Bright Galaxies on a Strikingly Straight and Narrow Filament
Authors: M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc'h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud, M. A. Zwaan
Figure caption: The fitted SED for the eight galaxies along the filament (G1–G8). The SEDs clearly demonstrate that G3–G7 are actively star-forming galaxies while G1, G2, and G8 (the three galaxies at the two ends of the filament) seem to be passive galaxies (with no emission lines). The physical properties of all galaxies, obtained from the best-fitted SEDs, are listed in Table 1.
Paper: Investigating the Electron-capture Supernova Candidate AT 2019abn with JWST Spectroscopy
Authors: Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Kishalay De, Michael E. Ressler, Ori D. Fox, Matthew J. Hankins
Figure caption: Photometry of the two prototypical ILRTs and AT 2019abn (black) at 4.5 μm. The SN 2008S (red) and NGC 300 2008-OT (blue) data points and the circular AT 2019abn points are Spitzer IRAC Channel 2 photometry points. The open diamond AT 2019abn points are from WISE Band 2 (4.6 μm), while the final star AT 2019abn point is a synthetic photometry point created using the Spitzer IRAC Channel 2 response with the JWST NIRSpec spectrum of AT 2019abn. The solid horizontal lines, color-coded by object, represent the 4.5 μm progenitor luminosities for each object as measured by Spitzer IRAC, with dashed 5σ uncertainties. At late times SN 2008S and NGC 300 2008-OT both faded below the level of their progenitors. At the time of our JWST observation AT 2019abn had faded significantly but had not yet faded below the 4.5 μm luminosity of its progenitor.
Paper: Investigating the Electron-capture Supernova Candidate AT 2019abn with JWST Spectroscopy
Authors: Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Kishalay De, Michael E. Ressler, Ori D. Fox, Matthew J. Hankins
Figure caption: MIR spectra of AT 2019abn and NGC 200 2008-OT with MIRI LRS and Spitzer IRS, respectively, as well as examples of various classes of PAH features (A. G. G. M. Tielens 2008). Note the similarities in the broad feature at 8.25 μm and also the differences in the 6.3 μm feature, which is strongly present in the class C spectrum, weaker in AT 2019abn, and entirely absent in NGC 300 2008-OT. We also show an example of a mixed-chemistry LBV that shows class B PAH features in addition to silicate features.
Paper: Investigating the Electron-capture Supernova Candidate AT 2019abn with JWST Spectroscopy
Authors: Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Kishalay De, Michael E. Ressler, Ori D. Fox, Matthew J. Hankins
Figure caption: Combined NIRSpec and MIRI LRS spectra of AT 2019abn observed 1421 days after the explosion. There is good agreement between instruments in the region of overlap. AT 2019abn exhibits a red continuum with broad emission features in the MIR characteristic of PAHs.
Paper: Investigating the Electron-capture Supernova Candidate AT 2019abn with JWST Spectroscopy
Authors: Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Kishalay De, Michael E. Ressler, Ori D. Fox, Matthew J. Hankins
Figure caption: pyPAHdb fit of the continuum-subtracted MIR spectrum of AT 2019abn. Note that the theoretical models predict a slightly stronger feature at 6.3 μm than is actually present.
Paper: Signatures of Rapidly Rotating Stars with Chemically Homogeneous Evolution in the First Galaxies
Authors: Boyuan Liu, Yves Sibony, Georges Meynet, Volker Bromm
Figure caption: Ratio between nebular and stellar luminosities in rest-frame UV (1500 ± 50 Å) from an instantaneous starburst and continuous star formation (starting at t = 0) with a constant rate over timescales tSF = 10, 30, and 100 Myr (clockwise) for the Yggdrasil models (E. Zackrisson et al. 2011), assuming no leakage of ionizing photons (optimistic nebular emission). Among these are two models for Pop III stars with top-heavy IMFs: a Salpeter-like power law (﹩dN/d{m}_{\star }\propto {m}_{\star }^{-2.35}﹩) in the range m⋆ ∈ [50, 500] M⊙ (Pop III.1, solid) and a log-normal distribution with characteristic mass m⋆,c = 10 M⊙ and dispersion (in ﹩\mathrm{ln}{m}_{\star }﹩) σ = 1 for m⋆ ∈ [1, 500] M⊙ (Pop III.2, dashed), one Pop III model with a P. Kroupa (2001) IMF in m⋆ ∈ [0.1, 100] M⊙ (dashed–dotted), three Pop II models with the same P. Kroupa (2001) IMF and different metallicities: Z = 0.0004 (dotted), 0.004 (long dashed), 0.008 (dashed–dotted-dotted), and a Pop I (densely dashed) model with the same P. Kroupa (2001) IMF and Z = 0.02. For the cases with continuous star formation, we are mainly interested in the results at t = tSF (labeled with vertical lines), which denotes the moment of observation, i.e., when the galaxy has been forming stars for a duration of tSF.