Ca II Absorbers in the Sloan Digital Sky Survey Data Release 9

Transcription

1 Ca II Absorbers in the Sloan Digital Sky Survey Data Release 9 Gendith Sardane Department of Physics & Astronomy PITTsburgh Particle Physics Astrophysics and Cosmology Center University of Pittsburgh, PA December 2, 213

2 Outline I. Introduction/Motivation II. Survey Details III. Statistics IV. Imaging V. Summary

3 I. Search for Ca II in the SDSS In an SDSS spectrum : Look Back Time, GYr Redshift HI Ly a CIV OVI MgII CaII.

4 Motivation Ca II λλ 3934,3969 ÅÅ gives access to the very low redshift Universe. It is a rare class of absorber under-utilized, under represented and under-studied. Strong Ca II systems preferentially reside in dense, dusty, neutral, metal-rich, molecular H 2 -bearing environments the reservoirs for SF (Wild & Hewett, 25, Wild et al 26, Wild et al 27, Nestor et al 28, Zych et al 27, Zych et al 29) Ca II absorber regions exhibit higher SFRs than other absorber regions (Zych et al 28, Zhu & Menard 213) Host galaxies as faint as ~.1L* can be studied with SDSS images

5 Search for Ca II in SDSS 1. SDSS DR9 spectroscopic QSOs brighter than i = z QSO >.1 3. Exclude BAL QSOs (Paris et al. 212, Shen et al. 211 ) 4. Searched a total of roughly 95, QSOs 5. Search excludes the Lyalpha forest Number QSO of Number QSOs QSO Redshift

6 Search for Ca II in SDSS : Data Reduction Pipeline Spectrum: wavelength, flux, error Fit Continuum: Splines and Gaussians Flux [ 1 17 ergs/s/cm2/ang ] 4 CIV 2 C III ] Mg II 1 4 Linefinder to find candidate CaII absorbers, separated zqso & z = by at least 6, km/s zqso Observed Wavelength, Angstroms Visual inspection to remove spurious systems. Apply significance &doublet ratio cuts = 441 candidates Normalized Flux Normalized Flux <z ABS > Observed Wavelength, Angstroms 51

7 8 Observed Redshift and Rest Equivalent Width Distributions < z abs >.58 < W λ3934 >.77 Å 6 Number Redshift, z abs Stats: Cuts : W λ3934 5σ, W λ σ, 1-σ DR DR 2+σ DR Number of systems= W [Å] DR = W λ3934 λ3969 W

8 g(w 3934,z)= Cumulative Path length, g(w) Sightline Coverage Survey Sensitivity Function NX LOS i=1 H(z z min(i) )H(z max(i) z)h[w ]H[W ] Wavelength, Angstroms W min =.3Å W min =.6Å W min = 1.Å W min = 2.Å W min = 4.Å WRedshift, min z, Angstroms

9 The Corrected Equivalent Width Distribution Number of Detections Cumulative Path length, g(w) X W [Å] Observed W λ3934 [ Å ] min W, Angstroms W min [ Å ] dn dw 3934 = N weak exp Wweak! W N strong exp Wweak Wstrong! W 3934 Wstrong 2 X ln( N/ W 3934) Maximize Likelihood of the distribution: p(w i ; ) = W [Å] Z W max g(w i )f(w i ; ) W min g(w )f(w ; )dw

10 Corrected Rest Equivalent Width Distributions dn dw 3934 = N weak W weak exp W 3934 W weak! + N strong W strong exp! W 3934 Wstrong 1 1 TWO Populations! log 1 ( N/ W ) MLE Parameters : Parameter! Weak! Strong! N*!.229 ± ±.14 5 W*[A]!.146 ± ± W [Å]

11 Ca II Equivalent Width Distribution vs Mg II & C IV 1 log 1 ( N/ W ) Ca II Mg II C IV W [Å]

12 Evolution? 3 25 z range z BIN = [[.3,.3,.41.42) ] z range z BIN = [.42, [.42,.72) ] z range z BIN = [[.72,.72, ] ] Number ln( N/ W 3934) z BIN = [.3,.41 ] z range = [.3,.42) z range = [.42,.72) z BIN = [.42,.72 ] W 3934 [Å] z BIN = [.72,1.34 ] z range = [.72, 1.34]

13 1 log 1 ( N/ W ) W [Å]

14 Redshift Number Density 1. W lim >.3Å W lim >.6Å dn/dz.1.1 W lim > 1.Å lim W > 1.5Å NEC z ABS z ABS

15 Redshift Number Density : CaII vs MgII 1. Redshift Redshift dn/dz W.3 Å 3934 W.3 Å Mg II NEC Ca II NEC Lookback Time, Gyr W.6 Å 3934 W.6 Å Mg II NEC Ca II NEC Lookback Time, Gyr.1.1.1

16 Absorber Galaxy Connection 1. Find the average number density of galaxies around Ca II-absorbing QSOs from SDSS images as a function of angular distance, redshift and limiting magnitude 2. At z =.15, the limiting magnitude of SDSS corresponds to L ~.3L* 3. Background is determined from non-caii absorbing QSOs

17 Lines of Sight with Absorbers log [Average Number per arcmin 2 per LOS] z = [.2,.5) Brighter than r SDSS < 19.3 z = [.11,.12) Brighter than r SDSS < 21.5 z = [.5,.8) Brighter than r SDSS < 2.6 z = [.12,.14) Brighter than r SDSS < 21.9 z = [.8,.11) Brighter than r SDSS < 21.3 z = [.14,.15) Brighter than r SDSS < 22. radius, arcsec

18 Some Ca II absorbers are Associated with very Luminous, Low-Impact Parameter Galaxies z abs =.47 z abs =.114 z abs =.113 z abs =.242 L =1.4L* L = 1.3L* L = 1.3L* L = 9.5L* b = 5 kpc b = 8 kpc b = 21 kpc b = 25 kpc

19 Are all Ca II absorbers associated with moderately luminous, low-impact parameter galaxies? No.

20 Cases with the Lowest Redshifts : z abs <.8 Number of Detections Mean Luminosity =.15L * Median Luminosity =.4L * Minimum Luminosity =.1L * Maximum Luminosity = 1.35L * Number of Detections Nearest Neighbor Luminosity [L * ] Minimum Impact Parameter [kpc] Brighter than.1l * Brighter than.1l*

21 Ca II at zabs =.655: Where is the absorbing galaxy? CaII Absorption Spectrum SDSS r-band image Normalized Flux z =.655 S S S S Observed Wavelength, Angstroms S Spectrum: W 3934 = 1.1 ±.2 W 3969 =.5 ±.2 At minimum b: b min ~ 43 r (b min )= 21. b min ~ 53 kpc L(b min ) ~.3 L* S : star-like Arrows: Blue QSO Red Galaxy

22 Ca II at zabs =.636: Where is the absorbing galaxy? CaII Absorption Spectrum SDSS r-band image Normalized Flux.8 z = Observed Wavelength Spectrum: W 3934 =.25 ±.5 W 3969 =.26 ±.5 At minimum b: b min ~ 74.6 r (b min ) = 2.7 b min ~ 9.2 kpc L(b min ) ~.4L*

23 Summary Conducted a search of Ca II λλ 3934,3969 AA doublet from ~ 95, quasars in SDSS DR9. Rest equivalent width distribution is fit very well by a double power-law model, with little or no evolution with redshift. The redshift number density is consistent with the no evolution curve at > 99%, and at least an order of magnitude smaller than Mg II. Very few Ca II absorbers are associated with bright, lowimpact parameter galaxies. In some cases, there is no evidence for plausible absorbing galaxies.