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RemoveYoung (RY) A tool for the removal of the young stellar - PowerPoint PPT Presentation

Mar 23, 2023 •494 likes •784 views

RemoveYoung (RY) A tool for the removal of the young stellar component within an adjustable age cutoff (based on Gomes & Papaderos 2016, A&A, 594, A49) Polychronis Papaderos and Jean Michel Gomes Institute of Astrophysics and Space

  1. RemoveYoung (RY) A tool for the removal of the young stellar component within an adjustable age cutoff (based on Gomes & Papaderos 2016, A&A, 594, A49) Polychronis Papaderos and Jean Michel Gomes Institute of Astrophysics and Space Sciences (IA)

  2. Motivation Instantaneous SF model (Salpeter IMF & solar metallicity) a tiny mass fraction of young (low M/L ratio) 3 mag stars can dominate the light (optical morphology) and overshine faint structural/morphological features in the underlying old stellar component of a galaxy (for example, relics from minor mergers) → the stellar surface density Σ  (M ⊙ /pc 2 ) is in some respects a more useful & robust quantity than the optical/NIR surface brightness μ (mag/arcsec 2 ) … however, Σ  is not an observable ... Starburst99 (Leitherer et al. 1999) μ (mag/arcsec 2 ) can strikingly differ from Σ  … but the latter (more specifically, the intrinsic stellar mass density ρ  (M ⊙ /pc 3 ) determines, together with ρ (gas+DM) ) the gravitational potential of a galaxy

  3. Techniques for 2D determination of Σ  (… which is dominated by older (higher M/L) stars) near-infrared imaging … but i) nebular continuum can be important in starburst galaxies Near IR C o n t r i b u t i o n o f n e b u l a r e m i s s i o n i n i n d i v i d u a l fj l t e r s Krüger et al. (1995) b : burst parameter = M ✶ (starburst) /M ✶

  4. Techniques for 2D determination of Σ  ii) NIR imaging does not permit to isolate the luminosity output from stars older than a user-defined cutoff (e.g. with t > 10 8 yr) Noeske et al. (2003)

  5. Techniques for 2D determination of Σ  NIR Conroy (2014) The young & intermediate-age stellar component contributes significantly to the emission in the NIR J, H and Ks (~1-2.2 μm) bands with optical/NIR photometry it is impossible to isolate the emission of stars younger than a certain age (for example, exclude pre-AGB stars with an age <10 8 yr)

  6. Techniques for 2D determination of Σ  determination of Σ  by spaxel-by-spaxel SED fitting (e.g. Wuyts+12) Wuyts et al. (2012): SED fitting using 7 HST bands ( ACS + near-IR WFC3) … this approach does not permit to strip off galaxy images from stars younger than an adjustable cutoff t cut

  7. Motivation behind the development of RemoveYoung Cases where bi-dimensional subtraction of the light contribution from stars younger than an adjustable cutoff t cut could add further insights into the assembly history of galaxies … (?) Examples: Propagation of star-forming activity in interacting/merging systems like the Antennae, or low-mass starburst galaxies near and far, such as blue compact dwarf (BCD) galaxies, green peas (GPs) and tidal dwarf galaxies (TDGs) :: Subtraction of stellar populations with an age t 1 … N offers a means to study a) how SF is synchronized on galactic scales and b) SF propagation effects (incl. estimates of the SF propagation velocity) Subtraction of the starburst component → study of the underlying galaxy host in BCDs Galaxies in galaxy clusters: initial SF episode, ram pressure stripping & galaxy harassment Assembly history of massive early-type galaxies: how has μ (R) and Σ  evolved over, say, the past 9 Gyr (since z ~1.4)?

  8. BCDs: Profile decomposition into the SF component and the underlying host (with the goal of determining μ and Σ for the host galaxy) plateau Papaderos et al. (2002) P 25 , E 25 : isophotal radius of the star-forming and LSB component line-of-sight intensity contribution of the SF component: ~40% at P 25 , 4% at E 25

  9. The pair of young BCD galaxy candidates SBS 0335-052 E&W (see discussion in Pairwise galaxy formation and galaxy downsizing ; Papaderos 2012) Pustilnik et al. (2001) SBS 0335-052: HI cloud with a projected size of 70×20 kpc; mass of ~10 9 M ⊙

  10. SBS 0335-052E: formation through SF propagation ● Study of the V-I color and spatial distribution of stellar clusters using HST data → ● galaxy is forming in a propagating mode from northwest to southeast with a mean velocityof ~20 km/s. Slit1 7 Papaderos et al. (1998) HST/WFPC2, V band HST/WFPC2, I band, unsharp masked

  11. Starburst activity in BCDs Super-Star Clusters Henize 2-10 Nearby (D=8.7 Mpc) BCD Starburst since 10 7 yr (Conti & Vacca 1996, Papaderos & Fricke 1998) 60 pc Wolf-Rayet features Papaderos et al. (2006) Young Stellar Clusters (YSCs) a) diffuse component of low-mass YSCs ( ≃ 10 3 M ⊙ ) b) compact & massive YSCs “Super-Star Clusters” (SSCs)

  12. Henize 2-10: H α supershells and large-scale gas outflows a) b) Papaderos & Fricke (1998) Papaderos & Fricke (1998) H  equivalent width map ROSAT HRI X-ray map a) mechanical luminosity for a Star Formation Rate of 1 M ⊙ yr -1 as a function of time Luminosity Power at t=10 7 yr : 4×10 41 erg s -1 (total energy injected into the ISM: 4.5×10 55 erg) b) bipolar outflow of hot and metal-enriched gas from the starburst component, expanding with velocities of ≥ 200 km s -1 into the ambient interstellar medium.

  13. Synchronization & propagation of SF activities in blue compact galaxies ESO 338-IG04 Östlin et al. (2003) 2.6 kpc Lagos et al. (2011) N e a r l y c o e v a l s t a r f o r m a t i o n o n s p a t i a l s c a l e s o f 0 . 2 - 0 . 5 k p c

  14. Tidal Dwarf Galaxies: does gas collapse within a gravitational potential formed by tidally ejected stars? Duc et al. (1997) TDGs: low-mass self-gravitating entities forming out of tidally ejected matter in interacting/merging galaxy pairs Barnes & Hernquist (1996)

  15. SFH of galaxies in galaxy clusters Chung et al. (2009) Poggianti et al. (1999) Sun et al. (2010)

  16. IC 3418 in the Virgo Cluster Hester et al. (2010) Quilis et al. (2000)

  17. RemoveYoung a post-processing tool for Spectral Population Synthesis ( SPS ) models

  18. SPS fit with STARLIGHT (Cid Fernandes et al. 2005): Decomposition of a galaxy spectrum into simpe stellar populations (SSPs: instantaneously formed stellar populations, fully characterized by their age, metallicity and IMF) Sánchez-Janssen et al. (2013) Secondary quantities, e.g. mass and luminosity-weighted stellar age

  19. The idea behind RemoveYoung (RY) i) Process spaxel-by-spaxel integral field spectroscopy (IFS) data of a galaxy in order to obtain its spatially resolved star formation history (SFH), which is encoded in the best fitting population vector PV (mass fraction (%) of simple stellar populations- SSPs of a given age and metallicity) ii) reconstruct the (UV-through-NIR) spectrum of the galaxy at each spaxel from the PV after removal of SSPs younger than an adjustable age cutoff t cut & convolve the synthetic SED with a set of filter transmission curves to obtain the 2D surface brightness distribution μ(x,y,band) of a galaxy after suppression of emission from stars younger than t cut (example: compute a synthetic SDSS g-band image for a galaxy after removal of stars younger than 100 Myr) iii) additionally, compute from the PV the Σ of stars older (or younger) than t cut → reconstruct in 2D the mass assembly history of the galaxy since t cut ( t 1 < t cut < t N )

  20. Application of RemoveYoung to single spectra Gomes & Papaderos (2016) left: SDSS spectrum of a galaxy as observed (orange & spectral fit in light-blue) and after application of RY for a t cut of 30 Myr (dark blue), 0.5 Gyr (green) and 5 Gyr (red) SDSS filter transmission curves shown as shaded areas

  21. Application of RY to integral field spectroscopy data Gomes & Papaderos (2016)

  22. RemoveYoung: Studies of the structural properties of the underlying host galaxy in BCDs Gomes & Papaderos (2016)

  23. Summary RemoveYoung (Gomes & Papaderos 2016) is a new spectral population synthesis post-processing tool that permits reconstruction of the SED and stellar mass M  after subtraction of stars older than an adjustable age cutoff t cut Simple extension of RY from 1D to 2D: spaxel-by-spaxel post-processing of PVs for IFS data modeled with a spectral population synthesis code (e.g. Starlight, Steckmap, FADO) → 2D determination of Σ  and the UV-NIR morphology μ(x,y) of a galaxy in various (currently ~ 20) photometric bands RY is a powerful new tool with significant potential of advancing our understanding on the assembly history of galaxies – from BCDs to ETGs (!): 2D applications of RY should include a critical consideration of (but could also help better understanding) effects of e.g. stellar diffusion/migration and a possible non-universality of the IMF in galaxies.

  24. Application of RemoveYoung on single spectra (check www.spectralsynthesis.org and www.iastro.pt for updates)

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