COSMOS Multi-Wavelength Data

In order to fulfill the scientific goals of the Survey, the COSMOS Team is collecting multi-wavelength data from the X-ray to radio domain. These data will be made available to the scientific community as they are gathered and analyzed, has the ACS images themselves.

We list in the following sections the observing time on at various facilities that we have proposed for. The tables use a color code to distinguish time that has been proposed for, awarded time and already collected data.

• Proposed: the proposal has been submitted to the appropriate Time Allocation Committee.
• Scheduled: the proposal has been accepted. Observations dates are given for classically scheduled time.
• Observed:the data has been collected.

• HST ACS Imaging
• Radio Imaging
• Sub-millimeter Imaging
• Mid and Far Infrared Imaging
• Optical/Near Infrared Imaging
  • Optical Imaging
  • Near Infrared Imaging
• Optical Spectroscopy
• Ultra Violet Imaging
• X-Ray Imaging

HST ACS Imaging

Although the data collected by the Hubble Space Telescope (HST) Advanced Survey Camera (ACS) is in the optical domain, this imaging plays an essential role in the COSMOS survey and deserves a separate section. The superb resolution and depth that are provided by ACS are essential for the study of the evolution of galaxy evolution and weak lensing. They are discussed in detail here.

So far, we have obtained the data to be taken during cycle 12. The combined image can be seen below (at a very low resolution). This image is monochrome, since we have so far only gathered one filter on the field. Image credits: Anton Koekemoer and the Cosmos Team.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
HST	ACS	I (F814W)	AB 27	2 sq. deg.	261 Orbits	NASA	Scoville	Cycle 12
					320 Orbits			Cycle 13
		g (F475W)	27 AB	9'x9'	9 Orbits			Cycle 12

Radio Imaging

Radio data is extremely useful to study the star formation and Active Galaxy Nuclei activity in galaxies. We plan to obtain a full coverage of the entire COSMOS field to a sufficient depth to sample the turnoff of faint number counts below a few hundredth of milli-Jansky at 1.4 GHz. So far, we have obtained 10 hours of data on the central region of the field at a shallower depth, and we have been granted the time to complete the observation of the entire field.

The combination of the radio data with the HST ACS data will give us insight on the morphology of the faint radio galaxy population. When combined with the spectroscopic information, it will allow us to study the effect of environment on the evolution of radio galaxies.

Thanks to the Far-IR/Radio correlation, it is also a very valuable tool to identify the sources that are detected in the sub-millimeter surveys that will be conducted over the COSMOS field. For example, with the VLA in A configuration at 1.4 GHz, the beam in the radio map is about 2'' Full width half maximum while the beam size of our Bolocam observations at 1.1~mm will be of the order of 30''.

More details on the VLA-COSMOS observations can be found on our dedicated web page. The data of the Pilot Project observed in August 2003 is now publicly available at IRSA.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
VLA	A Array	1.4 GHz	24 uJy/beam	0.35 sq. deg.	10 h.	NRAO	Schinnerer	August 2003
VLA	A Array	1.4 GHz	10 (17) uJy/beam	1 (2) sq. deg.	240 h.	NRAO	Schinnerer	Auntumn-Winter 2004
	C Array				24 h.			Spring-Summer 2005

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Sub-millimeter Imaging

Sub-millimeter observations (that is, at wavelength between 300 microns and 1 millimeter) probe the "dusty universe": distant luminous galaxies that emit most of their energy in the infrared, because all the stellar light (UV, Optical and Near Infrared) is absorbed by interstellar dust within these object, and reradiated at longer wavelength. For distant galaxies, the effect of cosmological redshift further shifts the bulk of their emission into the sub-millimeter domain.

The nature of this distant population of luminous infrared galaxies is still a matter of debate, especially as to what powers their high luminosity. Is it massive episode of star formation ("starburst galaxies"), massive black hole at their center ("Active Galaxy Nuclei") or a combination of the two ?

One thing is sure however: these galaxies are at least ten times more numerous in the past (i.e. at high redshift) than in the present (in the "local universe"). This population therefore undergoes a strong evolution. Observing this population in the COSMOS field will allow us to measure the effect of the environment on their evolution.

In order to reach this goal, we have used Bolocam at CSO to map the entire COSMOS field at a depth of a few milli-Jansky. This requires a substantial amount of time (a total 37 nights of observations have been awarded) and we have formed a collaboration between various institutions having access to the CSO: Caltech, JPL, and the University of Hawaii. Our observations have suffered from poor weather conditions in March 2004. The data reduction is in progress, so the sensitivities given in the table below are only estimates.

The central region of the COSMOS field, where radio data is already available will be also imaged with a bolometer camera at IRAM this winter at a depth of 1 mJy.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
IRAM 30m	MAMBO	250 GHz	2 mJy	20' x 20'	40 hours	IRAM	Bertoldi	Winter 2003
CSO	Bolocam	1.1 mm	2.1 mJy	1000 sq. arcmin.	37 n.	Caltech/JPL/UH	Blain/Glenn	Spring 2004

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Mid and Far Infrared Imaging

We will apply for time to cover the entire Cosmos field with the Spitzer Space Telescope in the Mid Infrared (5 to 30 microns) and the Far Infrared (30 to 300 microns).

In the Mid Infrared, and especially at 3.6 and 4.5 microns withe the IRAC instrument, we will detect the redshifted starlight of the distant galaxies. This will allow us to obtain very accurate photometric redshifts.

At longer wavelengths (5.8 and 10.8 microns), it is the hot dust from the galaxies that we will detect. It takes either an Active Galactic Nuclei or some very strong star formation to produce a significant dust emission below 6.5 microns. Also, the overall shape of the emission of the galaxy in the infrared, combined with the knowledge of its redshift will give us clues as to whether the source of the emission is actually due to a massive black hole or to the formation of stars.

In the far infrared, we will measure the overall dust content of galaxies. It is tightly correlated to the rate at which they form stars, and we will be able to study the effect of environement on star formation.

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Optical/Near Infrared Imaging

Optical and near infrared imaging of the COSMOS field from the ground will allow us to determine the colors of the galaxies, and therefore gain some hints on their type and their nature.

The immediate goal of these observations is to allow us to determine photometric redshifts in order to select the targets for the spectroscopic follow-up. In order to have good quality photometric redshifts, a wide wavelength coverage is necessary, from the U band (0.36) to the K band (2.2 microns).

Optical Imaging

We have so far obtained time for a complete coverage of the COSMOS field from the U band (0.36 microns) to the z band (0.9 microns), at a depth matching the one of our ACS observations, plus some time to obtain a full coverage in the I band for the selection of our spectroscopic sample.

The following Image is a very small fraction of the Cosmos field centered on a cluster of galaxies. It has been obtained by combining the various wide bands gathered with the Subaru telescope. Image credit: Yoshi Taniguchi and the Cosmos Team.

We have have been awarded 8 nights with Suprime CAM to observe the COSMOS field with narrow and intermediate filters in 2005. With the narrow band filters, we will look for high redshift galaxies in the field (z ~ 4.7 and 5.2) while the intermediate band filters will allow us to obtain better photometric redshifts for all galaxies.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
CFHT	MEGACAM	u*	26.9	2 sq. deg.	8 hours	UH	Sanders	Queue 03B
					4.7 hours			Queue 04A
					1.75 hours	France	Le Fèvre	Queue 03B
		i	24.9		4.75 hours
Subaru	Suprime-Cam	B	AB 27.4	2 sq. deg.	10 nights	Japan	Taniguchi	Jan-Feb 2004
		V	AB 27.2
		r'	AB 26.9
		i'	AB 26.9
		z'	AB 25.6
Subaru	SuprimeCAM	Intermediate Bands	AB = 26.5	2 sq. deg.	8 nights	Japan	Taniguchi	2005
		Narrow Bands	AB = 25.5

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Near Infrared Imaging

We have so far secured time to observe the complete COSMOS field in the J (1.1 micron) and K (2.2 micron) band. The central region of the field, where we have both g and I ACS data will be imaged to a greater depth at CFHT .

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
Kitt Peak	Flamingoes	Ks	21	2 sq. deg.	5 nights	NOAO	Mobasher	Feb. 2004
CFHT	CFHT-IR	K	23	9'x9'	3 nights	UH	Sanders	Feb. 2004
CTIO	ISPI	Ks	21	2 sq. deg.	5 nights	NOAO	Mobasher	Apr. 2004
UH 88"	ULBcam	J	20.4	2 sq. deg.	10 nights	UH	Sanders	Feb. 2004

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Optical Spectroscopy

We have obtained so far about 2000 redshifts in the field, from observations with VIMOS<

A large program will be proposed by the COSMOS team at ESO under the lead of J.P. Kneib. The objective is twofold:

1. We first aim to obtain spectroscopic redshifts for about 45,000 galaxies brighter than I=23. At this limiting magnitude, the morphology information provided by the ACS HST data is most accurate. The expected redshift distribution should extend to z~1.5, and peak at about z~0.6, where the weak lensing analysis of the COSMOS HST data will be the most efficient at tracing the massive structures in the field. This campaign will also allow us to finely calibrate our photometric redshifts obtained with the optical imaging.
2. We will then focus on the high redshift large scale structure, and obtain redshifts for an other sample of galaxies selected with 23 < I < 25 and with photometric redshift greater than 0.7. We expect to gather redshifts for the most massive galaxies in the field out to z~6

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Ultra-Violet Imaging

Ultra-Violet imaging -at wavelengths of 150 nanometer (Far-UV) and 225 nanometer (Near UV)- give us insight into the activity of star formation in galaxies, because this emission is mostly due to massive young stars that have a very short lifespan.

GALEX has observed the entire COSMOS Field (minus some regions containing stars to bright for the instrument), as part of its Deep Imaging Survey in the Guaranteed Time.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
GALEX		FUV/NUV	AB 26	2 sq. deg.	100 orbits	GTO	Schiminovich	2003/2004

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X-Ray Imaging

Imaging in the X-Ray domain allows to detection of Active Galaxy Nuclei and clusters of galaxies. Together with the ACS HST and spectroscopic data, the role of environment and galaxy morphology in the evolution of AGN activity will be measured.

We have so far secured 800 kiloseconds of observations with XMM/Newton, and we are applying for the next cycle to double this amount of time. The following image presents the data gathered so far. Image credit: Gunther Hasinger and the Cosmos Team. More images of our X-ray data can be found here and there.

We will also apply for Chandra time. The resolution of chandra images is finer, and we target zones where the density of source is high in the XMM image as well as optically selected cluster, using the photometric redshift technique discussed above.

Telescope	Instrument	Band	Depth	Area	Time	TAC	PI	Date
XMM/Newton	EPIC	0.5-2 keV	7e-16 cgs	2 sq. deg.	800 ksec	ESA	Hasinger	Winter 2003-Winter 2004
		2-10 keV	3e-15 cgs
XMM/Newton	EPIC	0.5-2 keV	5e-16 cgs	2 sq. deg.	800 ksec	ESA	Hasinger	XMM A04
		2-10 keV	2e-15 cgs

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