1. Introduction1. Introduction

3. Results : 3. Results : KKss Morphology at Morphology at zz~1~1

50% of disk-dominated galaxies are LIRGs.

90% of LIRGs have disk-dominated

morphologies (with grand design spirals for

some of them).

(c): Major contributors to the cosmic SF are galaxies

with disk-dominated and large-sized morphologies,

and LIRGs make up ~ 80% of the total SSFR.

Their SSFRs are a order of magnitude higher than

those of the local disk galaxies.

(c)

(d): We see almost the same profiles in the z850 and

Ks band. � There seems to be no significant (dusty)

nuclear SF regions (like for local Irr) in LIRGs.

Also, no clearly disturbed shapes were identified in either z850 or Ks-band by visual

inspection, and that was confirmed by Concentration-Asymmetry analysis (in z850).

2. Observation & Data Analysis2. Observation & Data Analysis

Source Detection on the Ks-band using SExtractor (Bertin & Arnouts 1996)

and Cross-correlation with MIPS/Chandra/Spectroscopic data.

� SED fitting using 10 bands (UBVizJHKs + IRAC 1,2)

� Photo-z (if necessary), Stellar mass, Rest-frame Color

� Sample Selection : z=0.8-1.2 and Ms>=1010 Msun

� 105 galaxies remained. Of them, 36 galaxies have 24um fluxes (~ LIRGs).

� SFR estimation from UV-continuum and/or 24um fluxes.

� 2-D profile fitting on the Ks-band using GALFIT (Peng et al. 2002)

Detection Completeness2-D fitting example (GALFIT)

MOIRCS Deep Survey (MODS)

- Target Field : GOODS-North

- Surveyed Area : ~ 33 arcmin2

GOODSN/MODS Ks (~33.3 arcmin2)

GOODSN ACS z850-band

4.4’

8’

(d1) (d2)

Radial Profile: Ks vs. z850

Disk-like Bulge-like(a)

(b): z~1 LIRGs have the stellar mass-size relation

similar to that of the local disk galaxies, but we can

see there is a little (factor of ~2) offset to the left.

(e): LIRGs dominate SFRD in all stellar mass bin.

(Is there a turn-over for contribution from LIRGs?

Uncertain due to the limit of 24um depth.)

The less massive galaxies have more contributions

to the total SFRD.

(f): Number density of high-mass

end (Ms>1011Msun) has been

already almost comparable to

that of the local.

Subtotal for n<2.5(f)

Stellar Mass Function @ z=0.8-1.2

4. Discussion4. Discussion

� Massive LIRGs must decline their SFs rapidly between z=1-0 (~8Gyr).

In our estimation, the decline occurs more rapidly than that of the cosmic SF, and

depends on the stellar mass. The more massive LIRGs have more rapid decline of SFs.

Total SFRD

Subtotal SFRD

(e)

Our Interpretation & Conclusion:The era “z~1” corresponds to the final phase of spiral galaxy formation.

LIRGs at z~1 are thought to be the progenitors of the local (massive) spirals

(inferred from similarities in size and number density), and they seem to have

‘disk-driven’ intense SFs (not by strong interactions).

However, their SFs have declined rapidly (faster than the decline of the

cosmic SF) with slight increase in their stellar masses. And their structure

formations as spiral galaxies would have completed in a few Gyrs.

In that sense, we can say that LIRG evolution leads the cosmic SF history.

(b)

Note:

Our data = rest-frame J-band @ z~1

Shen+03 = rest-frame I-band @ z~0.1

<Δlog10(Ms)>

~ 0.1±0.1

- Morphology as the Structure of Stellar Mass -

Resolution of the Ks-band

In the last decade, it has been observed that the cosmic star formation (SF) rate (SFR)

has declined very rapidly from z>1 to z=0. It has been also thought that Luminous

Infrared (IR) Galaxies (LIRGs; LIR>1011Lsun) are major star-forming population during

the active phase of the cosmic SF.

Recently, it has been considered that most of those distant LIRGs are massive spiral

(or irregular) galaxies and that they have important roles in the rapid decline of the

cosmic SF.

Therefore, in terms of the causes of the cosmic SF’s decline, it is essential to

understand how and where SF have occurred at z~1, especially for LIRGs.

In this work, we evaluate morphology of galaxies at z~1 measured in the near-IR

which is the good indicator of underlying stellar mass distribution as it is less affected

by dust obscuration and the recent SF activity. Then, we investigate galaxy evolution,

especially for LIRGs, from z~1 to the present.

We used the Subaru/MOIRCS JHKs deep imaging data (MOIRCS Deep Survey; MODS) with the publicly available data including HST/ACS and

Spitzer/MIPS to investigate the morphologies and the star-formation activities of galaxies at z~1 in the GOODS-North field.

The Ks-band data has the F.O.V. of ~33 arcmin2, the limiting magnitude of ~25.2 (5sigma, AB) and the seeing FWHM of ~0.4 arcsec. We

compiled the rest-frame optical to NIR morphologies, the star-formation (SF) rates (SFRs) estimated from the UV-continuum fluxes and/or MIPS

24um fluxes, and the multi-band (photometric) SEDs, and then constructed the stellar mass-selected sample (Ms>1010Msun) between z=0.8 and 1.2.

Galaxies with active SFs inferred from either UV or 24um flux are mostly Luminous InfraRed Galaxies (LIRGs; LIR>1011Lsun) and they have disk-

dominated morphologies with no clear signs of galaxy interaction in both z850-band (rest-frame B-band) and Ks-band (rest-J). Those LIRGs have

comparable sizes and number densities to those of the local massive spirals.

We conclude that (1) the LIRGs at z~1 are the progenitors of the local massive spirals, (2) the growth of their structures (stellar masses and sizes)

have been almost completed at z~1, and (3) their SFRs decrease faster than the cosmic SFR. Their high SFRs compared to the local galaxies are

thought of as the final phase of the structure formation including disk-dominated morphologies.

Masahiro Konishi (Subaru Telescope / Tohoku Univ.)

konishi@subaru.naoj.orgR. Suzuki, C. Tokoku, Y. K. Uchimoto, T. Yoshikawa, M. Akiyama, M. Kajisawa,

T. Ichikawa, M. Ouchi, K. Omata, I. Tanaka, T. Nishimura, and T. Yamada

P291Subaru International Conference 2007

Galaxy Morphologies and Star Formations at z~1