2024年3月13日发(作者：杞晶灵)

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DiscoveryofAVeryBright,Strongly-Lensedz=2Galaxyinthe

SDSSDR5

HuanLin

1

,ElizabethBuckley-Geer

1

,

1,2

,

1

,

Diehl

1

,DonnaKubik

1

,Jeff

1

,JamesAnnis

1

,n

1,3

,Masamune

Oguri

4

,NaohisaInada

5

ABSTRACT

Wereportonthediscoveryofaverybrightz=2.00star-forminggalaxy

thatisstronglylensedbyaforegroundz=0.422luminousredgalaxy(LRG).

ThissystemwasfoundinasystematicsearchforbrightarcslensedbyLRGsand

brightestclustergalaxiesintheSloanDigitalSkySurveyDataRelease5sample.

Follow-upobservationsontheSubaru8.2mtelescopeonMaunaKeaandthe

AstrophysicalResearchConsortium3.5mtelescopeatApachePointObservatory

confielensmodelforthesystem,

assumingasingularisothermalellipsoidmassdistribution,yieldsanEinstein

radiusofθ

Ein

=3.82±0.03

′′

or14.8±0.1h

−1

al

projectedmassenclosedwithintheEinsteinradiusis2.10±0.03×10

12

h

−1

M

⊙

,

andthemagnificationfactorforthesourcegalaxyis27±ingthelens

modelwithourgVrizphotometry,wefindan(unlensed)starformationratefor

thesourcegalaxyof32h

−1

M

⊙

yr

−1

,adoptingafiducialconstantstarformation

ratemodelwithanageof100MyrandE(B−V)=apparent

magnitudeofr=19.9,thissystemisamongtheverybrightestlensedz≥2

galaxies,andprovidesanexcellentopportunitytopursuedetailedstudiesofthe

physicalpropertiesofanindividualhigh-redshiftstar-forminggalaxy.

Subjectheadings:gravitationallensing—galaxies:high-redshift

–2–

uction

Stronglensingsystemsprovidethedualopportunitytostudyboththeforegroundmass

distributionalongthelineofsighttothelensandthephysicalpropertiesofthebackground

terisespeciallyusefulinstudiesofhigh-redshiftgalaxies,

forwhichlensingprovidesavitalboostintheapparentbrightnessofthesefaintobjects,

whichareotherwisedifficulttostudyindetail.

Formanyyearsthez=2.72systemcB58(Yeeetal.1996)servedastheprototypical

lensedhigh-redshiftLymanbreakgalaxy(,Steideletal.2003).Atr=20.4,it

isverybrightandtherebyallowedanumberofdetailedstudiesofthephysicalproperties

,Pettinietal.2000;Teplitzetal.2000).Recently

anumberofhigh-redshiftlensedsystemshavebeendiscovered,eitherserendipitouslyorin

systematicsearches,thatarebrighterthancB58(Smailetal.2007;Belokurovetal.2007),

includingthecurrentrecordholder,the“8o’clockarc,”atr=19.2(Allametal.2007).

ThesediscoverieshavebeenenabledbytheSloanDigitalSkySurvey(SDSS;Yorketal.

2000),whichprovidestheverylargesearchareaneededtosystematicallyfindtheserare

examplesofextremelybrightlensedhigh-redshiftgalaxies.

Inthispaperwereportonthediscoveryofanotherremarkablybright(r=19.9)strongly

lensedz=2.00galaxy,thefirstsystemwehaveconfirmedfromasystematicsearchprogram

peris

organizedasfollows:§2describesthearcsearchandthediscovery,§3describesthefollow-

upimagingandspectroscopythatledtoconfirmationofthesystemasagravitationallens,§4

describesthemodelingofthesystemincludingthephotometrymeasurements,§5describes

thesourcegalaxystarformationratemeasurements,andfinally§6presentsourconclusions.

WeassumeaflatcosmologywithΩ

M

=0.3,Ω

Λ

=0.7,andH

0

=100hkms

−1

Mpc

−1

,unless

otherwisenoted.

rchSample

TheSDSS(Yorketal.2000)isadigitalimagingandspectroscopicsurveythat,over

thecourseoffiveyears,mappednearlyonequarterofthecelestialsphereinfivefilterbands

(ugriz;Fukugitaetal.1996)downtor=22.2andobtainedspectrafor≈10

6

astronomical

objects(Adelman-McCarthyetal.2007).TheSDSScompleteditsfirstphaseofoperations

inJune2005andrecentlycompletedathree-yearextensionknownasSDSS-IIinJuly2008.

(Formoredetails,.)

WepreviouslyreportedtheserendipitousdiscoveryintheSDSSDataRelease4(DR4;

2024年3月13日发(作者：杞晶灵)

8

0

0

2

e

p

S

5

2

]

h

p

-

o

r

t

s

a

[

1

v

5

7

4

4

.

9

0

8

:

0

v

i

X

r

a

DiscoveryofAVeryBright,Strongly-Lensedz=2Galaxyinthe

SDSSDR5

HuanLin

1

,ElizabethBuckley-Geer

1

,

1,2

,

1

,

Diehl

1

,DonnaKubik

1

,Jeff

1

,JamesAnnis

1

,n

1,3

,Masamune

Oguri

4

,NaohisaInada

5

ABSTRACT

Wereportonthediscoveryofaverybrightz=2.00star-forminggalaxy

thatisstronglylensedbyaforegroundz=0.422luminousredgalaxy(LRG).

ThissystemwasfoundinasystematicsearchforbrightarcslensedbyLRGsand

brightestclustergalaxiesintheSloanDigitalSkySurveyDataRelease5sample.

Follow-upobservationsontheSubaru8.2mtelescopeonMaunaKeaandthe

AstrophysicalResearchConsortium3.5mtelescopeatApachePointObservatory

confielensmodelforthesystem,

assumingasingularisothermalellipsoidmassdistribution,yieldsanEinstein

radiusofθ

Ein

=3.82±0.03

′′

or14.8±0.1h

−1

al

projectedmassenclosedwithintheEinsteinradiusis2.10±0.03×10

12

h

−1

M

⊙

,

andthemagnificationfactorforthesourcegalaxyis27±ingthelens

modelwithourgVrizphotometry,wefindan(unlensed)starformationratefor

thesourcegalaxyof32h

−1

M

⊙

yr

−1

,adoptingafiducialconstantstarformation

ratemodelwithanageof100MyrandE(B−V)=apparent

magnitudeofr=19.9,thissystemisamongtheverybrightestlensedz≥2

galaxies,andprovidesanexcellentopportunitytopursuedetailedstudiesofthe

physicalpropertiesofanindividualhigh-redshiftstar-forminggalaxy.

Subjectheadings:gravitationallensing—galaxies:high-redshift

–2–

uction

Stronglensingsystemsprovidethedualopportunitytostudyboththeforegroundmass

distributionalongthelineofsighttothelensandthephysicalpropertiesofthebackground

terisespeciallyusefulinstudiesofhigh-redshiftgalaxies,

forwhichlensingprovidesavitalboostintheapparentbrightnessofthesefaintobjects,

whichareotherwisedifficulttostudyindetail.

Formanyyearsthez=2.72systemcB58(Yeeetal.1996)servedastheprototypical

lensedhigh-redshiftLymanbreakgalaxy(,Steideletal.2003).Atr=20.4,it

isverybrightandtherebyallowedanumberofdetailedstudiesofthephysicalproperties

,Pettinietal.2000;Teplitzetal.2000).Recently

anumberofhigh-redshiftlensedsystemshavebeendiscovered,eitherserendipitouslyorin

systematicsearches,thatarebrighterthancB58(Smailetal.2007;Belokurovetal.2007),

includingthecurrentrecordholder,the“8o’clockarc,”atr=19.2(Allametal.2007).

ThesediscoverieshavebeenenabledbytheSloanDigitalSkySurvey(SDSS;Yorketal.

2000),whichprovidestheverylargesearchareaneededtosystematicallyfindtheserare

examplesofextremelybrightlensedhigh-redshiftgalaxies.

Inthispaperwereportonthediscoveryofanotherremarkablybright(r=19.9)strongly

lensedz=2.00galaxy,thefirstsystemwehaveconfirmedfromasystematicsearchprogram

peris

organizedasfollows:§2describesthearcsearchandthediscovery,§3describesthefollow-

upimagingandspectroscopythatledtoconfirmationofthesystemasagravitationallens,§4

describesthemodelingofthesystemincludingthephotometrymeasurements,§5describes

thesourcegalaxystarformationratemeasurements,andfinally§6presentsourconclusions.

WeassumeaflatcosmologywithΩ

M

=0.3,Ω

Λ

=0.7,andH

0

=100hkms

−1

Mpc

−1

,unless

otherwisenoted.

rchSample

TheSDSS(Yorketal.2000)isadigitalimagingandspectroscopicsurveythat,over

thecourseoffiveyears,mappednearlyonequarterofthecelestialsphereinfivefilterbands

(ugriz;Fukugitaetal.1996)downtor=22.2andobtainedspectrafor≈10

6

astronomical

objects(Adelman-McCarthyetal.2007).TheSDSScompleteditsfirstphaseofoperations

inJune2005andrecentlycompletedathree-yearextensionknownasSDSS-IIinJuly2008.

(Formoredetails,.)

WepreviouslyreportedtheserendipitousdiscoveryintheSDSSDataRelease4(DR4;