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Feb 19, 2008 Joon Hyeop Lee 1 , Myung Gyoon Lee 1 , Changbom Park 2 , Yun-Young Choi 2 1 Seoul National University 2 Korea Institute for Advanced Study. SDSS-KSG Workshop. Multiwavelength Properties of the SDSS Galaxies in Various Classes. Introduction.

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Multiwavelength Properties of the SDSS Galaxies in Various Classes

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Multiwavelength properties of the sdss galaxies in various classes

Feb 19, 2008

Joon Hyeop Lee1, Myung Gyoon Lee1,

Changbom Park2, Yun-Young Choi2

1Seoul National University

2Korea Institute for Advanced Study

SDSS-KSG Workshop

Multiwavelength Properties of the SDSS Galaxies in Various Classes


Multiwavelength properties of the sdss galaxies in various classes

Introduction

1. Why “Galaxies in Various Classes”?

It is important to understand the relationships between galaxies with different features.

Why are you different from me?

Why galaxies are so diverse?

How galaxies form and evolve?

How different are the diverse galaxies?


Multiwavelength properties of the sdss galaxies in various classes

Introduction

1. Why “Galaxies in Various Classes”?

A systematic study based on a fine classification is necessary.

In many previous studies, galaxies have been investigated, using various classification: morphology, color, spectral features, and so on.

  • Morphology (early-type vs. late-type): Choi et al. (2007), ...

  • Color (red vs. blue): Martin et al. (2007), ...

  • Spectral features (passive vs. star-forming vs. Seyfert vs. LINER):

    • Mateus et al. (2006) ...

? early-type = red = passive ?

? late-type = blue = star-forming ?

NOT ALWAYS !

  • Blue early-type galaxies: elliptical morphology, but blue color.

  • (Abraham et al. 1999; Ferreras et al. 2005; Lee et al. 2006)

  • Passive spiral galaxies: spiral morphology, but no signal of current SF.

  • (Couch et al. 1998; Goto 2003; Yamauchi & Goto 2004)


Multiwavelength properties of the sdss galaxies in various classes

2. Why “Multiwavelength”?

Multi-wavelength data provide diverse information about galaxy evolution, such as dust contents, recent star formation history, and optically-obscured AGNs.

  • Chang et al. (2006): elliptical galaxies in the optical and NIR bands

  • Goto (2005): IR galaxies in the optical and IR bands

  • Ivezic (2002): radio galaxies in the optical and radio bands

  • Yi et al. (2005): early-type galaxies in the optical and UV bands

  • Anderson (2007): X-ray AGNs in the optical and X-ray bands

However, systematic studies using all wavelength data are not sufficient, yet.

  • Obric et al. (2006): a panchromatic study based on the SDSS DR1, using SDSS, ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSSand WENSS data.


Multiwavelength properties of the sdss galaxies in various classes

3. Purpose

Understand the properties of galaxies in various fine classes based on their morphology, color and spectral features, using multi-wavelength data.

Constraints on the large picture of galaxy evolution


Multiwavelength properties of the sdss galaxies in various classes

Data

  • Sloan Digital Sky Survey (SDSS)

  • - ugriz bands

  • 1.4” FWHM

  • 3800 – 9200Å

    spectroscopy

  • 5600 sq.degree

    (+ DR4plus, MPA catalog)

  • Infrared Astronomical Satellite (IRAS) Survey

  • 98% of all sky

  • 12, 25, 60 and 100 μm

mid- & far-infrared

optical

  • Faint Images of the Radio Sky at Twenty-centimeters (FIRST) Survey

  • 1.4 GHz (20cm)

  • 5” resolution

  • over 10000 sq.degree

  • Two Micron All Sky Survey (2MASS)

  • - JHKs bands

  • 3” FWHM

  • 99.998% of all sky

near-infrared

radio


Multiwavelength properties of the sdss galaxies in various classes

  • Galaxy Evolution Explorer (GALEX) Survey

  • FUV(1528 Å)

  • NUV(2271Å)

  • 4.5–6 .5” resolution

  • Roentgen Satellite (ROSAT) Survey

  • 0.1-2.4keV

  • all sky

  • 22” resolution

ultraviolet

X-ray


Multiwavelength properties of the sdss galaxies in various classes

Red

AGN

Seyfert

Early-type

Blue

HII

LINER

Late-type

Kauffmann et al. (2003)

Kewley et al. (2006)

Park & Choi (2005)

Lee et al. (2006)

→Passive,HII, Seyfert, LINER

→Early-type galaxies

Late-type galaxies

→Red galaxies

Blue galaxies

Analysis

Galaxy Classification

(1) Morphology (2) Color (3) Spectral Features


Multiwavelength properties of the sdss galaxies in various classes

blue

red

early-type

late-type

passive

HII

Seyfert

LINER

color

spectral features

morphology


Multiwavelength properties of the sdss galaxies in various classes

2.Sample Selection

K-correction:Blanton et al. (2003)

Evolutionary correction:Tegmark et al. (2004)

Completeness limit: 14.5<rpet<17.77


Multiwavelength properties of the sdss galaxies in various classes

Results

1.Near-Infrared (2MASS)

(1)REGs have consistent colors with the 6-8 Gyr SSP .

The pRLGs have consistent colors with REGs, and RLGs are located on a sequence from REG colors to decreasing (u-r) and increasing (r-Ks).

The pBEGs, lBEGs are consistent with young SSP, but hBEGs, sBEGs have bluer (u-r) and redder (r-Ks).

BLGs have younger mean stellar age than any other morphology-color class.


Multiwavelength properties of the sdss galaxies in various classes

Results

1.Near-Infrared (2MASS)

(1)REGs have consistent colors with the 6-8 Gyr SSP .

The pRLGs have consistent colors with REGs, and RLGs are located on a sequence from REG colors to decreasing (u-r) and increasing (r-Ks).

The pBEGs, lBEGs are consistent with young SSP, but hBEGs, sBEGs have bluer (u-r) and redder (r-Ks).

BLGs have younger mean stellar age than any other morphology-color class.


Multiwavelength properties of the sdss galaxies in various classes

Results

1.Near-Infrared (2MASS)

(1)REGs have consistent colors with the 6-8 Gyr SSP .

The pRLGs have consistent colors with REGs, and RLGs are located on a sequence from REG colors to decreasing (u-r) and increasing (r-Ks).

The pBEGs, lBEGs are consistent with young SSP, but hBEGs, sBEGs have bluer (u-r) and redder (r-Ks).

BLGs have younger mean stellar age than any other morphology-color class.

Galactic Downsizing

(Cowie et al. 1996)


Multiwavelength properties of the sdss galaxies in various classes

2.Mid- and Far-Infrared (IRAS)

Blue galaxies are better detected than red galaxies (Obric et al. 2006), and late-type galaxies are better detected than early-type galaxies.

99% of the IRAS-detected objects are non-passive.

(3)BLGs are better detected than RLGs, which shows that the dominant factor to make RLGs red may be the bulge-to-disk ratio rather than dust contents.


Multiwavelength properties of the sdss galaxies in various classes

Best et al. (2005) and Croft et al. (2007) showed that the fraction of radio-loud AGN host galaxies is a strong function of stellar mass.

Early-type radio source: radio-loud AGNs.

Late-type radio source: star formation regions.

3.Radio (FIRST)


Multiwavelength properties of the sdss galaxies in various classes

The non-passive RLGs have consistent (NUV-r) colors with BEGs.

The pRLGs have consistent UV colors with non-passive REGs.

The pBLGs have very blue UV colors.

4.Ultraviolet (GALEX)


Multiwavelength properties of the sdss galaxies in various classes

The non-passive RLGs have consistent (NUV-r) colors with BEGs.

The pRLGs have consistent UV colors with non-passive REGs.

The pBLGs have very blue UV colors.

UV colors are very sensitive to recent star formation history.

The pBEGs are not well explained by the SSP model.

4.Ultraviolet (GALEX)


Multiwavelength properties of the sdss galaxies in various classes

The non-passive RLGs have consistent (NUV-r) colors with BEGs.

The pRLGs have consistent UV colors with non-passive REGs.

The pBLGs have very blue UV colors.

UV colors are very sensitive to recent star formation history.

The pBEGs are not well explained by the SSP model.

4.Ultraviolet (GALEX)


Multiwavelength properties of the sdss galaxies in various classes

Red galaxies are better detected than blue galaxies in the X-ray (73% of x-ray sources are red galaxies), which is consistent with Obric et al. (2006).

The sample sizes are too small to compare the X-ray properties between fine classes.

5.X-ray (ROSAT)


Multiwavelength properties of the sdss galaxies in various classes

Summary

  • The NIR colors show that REGs are well explained by SSP models, and that RLGs may have both old and young populations. BEGs seem much younger than REGs, and BLGs have the youngest age.

  • Dust extinction may not be the dominant factor to make RLGs look red, because they are less detected in the MIR and FIR bands, than BLGs.

  • The bright REGs are obviously better detected in the radio band, using the FIRST data, than faint REGs, whereas the radio detection rate of late-type galaxies is not very dependent on their absolute magnitude, except for pRLGs.

  • The UV colors of BEGs are explained by old SSP galaxies with additional young stellar populations. The pRLGs have very consistent UV colors with non-passive REGs.

  • Since the X-ray detection rate in each class, using the ROSAT data, is too small, meaningful discussions for individual classes are very difficult in the X-ray bands.


Multiwavelength properties of the sdss galaxies in various classes

In this study, the projected distance to the 5th-nearest neighbor is defined as:

The projected comoving distances to 5th-nearest neighbors from a target objects, within a redshift slice limited as ±1000 km/s with respect to the recession velocity of the target object, in the given volume.

6.Environmental Effects

Distance to the nth-nearest neighbor

- Cooper et al. (2005) showed that the projected n-th nearest neighbor distance measure (Dressler 1980) provides more accurate estimate of local density over a continuous and broad range of scales, than the aperture count (Hogg et al. 2003) or the Voronoi volume (Ramella et al. 2001).


Multiwavelength properties of the sdss galaxies in various classes

radio

NIR

MIR+FIR

?

X-ray

UV


Multiwavelength properties of the sdss galaxies in various classes

blue

red

early-type

late-type

passive

HII

Seyfert

LINER

color

spectral features

morphology


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