The Prevalence and Properties of Outflowing Galactic Winds at z = 1

transcript

Katherine A. Kornei (UCLA) UC Riverside Astronomy Talk January 27, 2012

Crystal Martin (UCSB)

Alice Shapley (UCLA)

Alison Coil (UCSD)

Several important people.

Galaxies are not closed boxes.

enrich the IGM in metals/dust

…quench star formation

…regulate black hole growth

Outflowsoutfl

AGN feedback?

cold streams?

AGN feedback?

Outflows are seen in local starbursts.

HST/ACS BVIHα (M. Westmoquette)

M82 (z=0.0008)

Outflows can be inferred through line offsets.

MgI MgII

Given outflowing material between the observer and the galaxy:

[OII] 3727 ÅNebular line – at zsys zsys

Velocity (km/sec)

ixel MgII 2796/2803

MgI 2852

Outflowing gas will be blueshifted with respect to nebular lines tracing star forming regions.

Galaxies near and far show blueshifted absorption lines.

ULIRGz = 0.2

LBGsz = 3

Interstellar Absorption

A variety of absorption lines are used to probe outflows.

Na I D ≈ 5900 Å z z = 0.5 1.0 3.0

Fe II/Mg II ≈ 2600 Å H I + others ≈ 1200 Å

Reddy et al. 2008

The necessary data set.

Spectroscopy of lines tracing outflowing gas

lines tracing the systemic redshift

+ Photometry for calculating stellar masses, etc.

+ Ancillary data for obtaining dust-corrected SFRs, morphologies, galaxy inclinations, etc.

The ideal data set.

50,000 galaxies at z ≈ 1 in 3.5 deg2

DEIMOS on Keck II (90 nights: ‘02-’05)

DEEP2 survey (the origin of our sample).

Slitmasks with 120 targets

R = 5000 (70 km s-1)

Resolved [OII] doublets

≈ 1 hour integration

Color cuts in 3/4 fields for z > 0.75

z < 0.75z > 0.75

Extended Groth Strip – no color cuts and lots of ancillary data.

HST imaging (F606W, F814W)

Spitzer imaging (IRAC, MIPS)

GALEX imaging (FUV, NUV)

The ideal data set. Photometry, imaging

The necessary data set. Lines tracing outflows & systemic z

LRIS observations to cover lines tracing winds.

LRIS: 3400-6700 Å LRIS: 7200-9000 Å

DEIMOS: 6500-9100 Å

[OII] (zsys)CIV, FeII, MgII, MgI (zout)

212 objects; B < 24.5 1.19 < z < 1.35 = CIV 1549, MgI 2852 coverage

Rest Wavelength (angstroms)

Si II, C IV

Fe IIFe II

Al II Mg I

Many analyses are possible. LRIS spectroscopy

fit FeII absorption lines to determine zout

measure fine structure FeII* emission lines

define zsys ([OII], Balmer series)

characterize MgII emission

72 LRIS objects are in the Extended Groth Strip.

EGS (72)

Other fields (140)

star-formation ratesdust attenuationsHST imaging

More analyses are possible for EGS objects. LRIS spectroscopy

fit FeII absorption lines

measure fine structure FeII* emission lines

define zsys ([OII], Balmer series)

characterize MgII emission

HST imaging

morphologies

colors

galaxy areas

inclinations

SFRs, dust attenuations from GALEX

Blue, star-forming galaxies at z = 1.

t al.,

Defining systemic and outflow velocities.

zsyszout Define a systemic reference frame, ideally from the LRIS spectra. Fit multiple emission lines ([OII], OIII, Balmer) using template spectra.

tilted [OII] lines(small fraction of

sample)

resonance abs.

fine structureemission

2250, 2260 2344, 2374 2587 Å

A physical model for fitting absorption lines.

A single component fit with 4 free parameters.

covering fraction

op. depth at line center

line center

Doppler parameter

Primary quantity of interest is λ0, from which we estimate an outflow velocity.

Blueshifted FeII absorption features are not ubiquitous in the sample.

t al.,

12100420 z = 1.20

t al.,

Inflow?

Other outflow diagnostics: MgII, FeII*

Velocities from FeII

Outflows Inflows

The strength of outflows is correlated with various galaxy properties.

ity (k

SFR (M*/yr)

dwarf starbursts

ULIRGs

Outflow velocity increases with increasing star formation rate.

Chen et al. 2010

edge-on

face-on

Outflows not seen in edge-on systems.

face-on edge-on

No trend between outflow velocity and star-formation rate.

Martin 2005 1000 Msun yr-10.1 Msun yr-1

Are outflows correlated with star-formation rate surface densities?

SFR estimate area estimate

UV, 24 μm, emission lines, etc.

Half-light radius?Petrosian radius?

A = πR2F606W

Clumpy objects at high z – need a better area estimate that traces luminous regions.

A new technique for estimating galaxy areas.

Given “clumpy” galaxies:

Include only those pixels brighter than a certain surface brightness

threshold, thereby flagging clumps.

Petrosianarea

Clumparea

Higher star-formation rate surface density objects show larger blueshifts.

No trend seen:

Rubin et al. 2010(used half-light radius)

Steidel et al. 2010(ground-based imaging)

Kornei et al., in prep.

Composite spectra show same trends as individual objects.

High Low

Star-formation rate surface density composites::

High: dV = -31 ± 7 km s-1 Low: dV = 44 ± 15 km s-1

High: dV = -300 km s-1

Mg II shows more kinematic variation than Fe II

SN IIFeII FeII

MgII in supernova ejecta; FeII merely entrained?

The geometry of outflowing winds at z = 1.

Chen et al. 2010

edge-on

face-on

face-on edge-on

Estimate inclination from axis ratios from HST imaging:

i = cos-1(b/a)b

Face-on galaxies show stronger blueshifts than edge-on systems.

More edge-on: dV = 28 ± 11 km s-1More face-on: dV = -19 ± 9 km s-1

Inclination composites::

Low High

face-on edge-on

Mergers are not required to drive outflows.

t al.,

Gini (G) – measure of how light is distributed in a galaxy

high G low G

M20 – second order moment of a galaxy’s 20% brightest pixels

high M20low M20

Fine structure FeII* emission.

zsysv = 0

v = +100v = -100

2600 Å (resonance)

2626 Å (fine structure)

Leitherer et al. 2010

probing very different scales at z = 1 and z = 0

Does this emission come from star forming regions or from outflows?

8400 pc/” 16 pc/”

FeII* emission is prevalent.

Stacks of FeII* emitters/non-emitters FeII* emitters FeII* non-emitters

The strongest FeII* emitters are bright and blue.

FeII* emission appears to be ubiquitous

FeII, FeII*

stronger FeII* = stronger MgII emission

Complexities of the MgII feature at ≈ 2800 Å.

Composite spectrum Individual spectra show MgII emission

AGN? (Weiner et al. 2009)

Scattered wind? (Rubin et al. 2010)

MgII and FeII absorption are kinematically distinct.

t al.,

Measuring an outflow velocity from MgII

2796 Å (resonance)

A resonantly trapped transition.

where 90% of the continuum is met.

No correlation:SFR and Vmax

Significant correlation:SFRSD and Vmax

Summary.

Reddy et al. 2008

Petrosianarea

Clumparea

LRIS: 3400-6700 Å LRIS: 7200-9000 Å

DEIMOS: 6500-9100 Å

CIV, FeII, MgII, MgI (zout)[OII] (zsys)

Outflow velocity most strongly correlated with the concentration of star formation.

The Prevalence and Properties of Outflowing Galactic Winds at z = 1

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