J/AJ/148/117 Imaging and spectroscopy in Lynx W (Jorgensen+, 2014)
RX J0848.6+4453: the evolution of galaxy sizes and stellar populations in a
z = 1.27 cluster.
Jorgensen I., Chiboucas K., Toft S., Bergmann M., Zirm A., Schiavon R.P.,
Grutzbauch R.
<Astron. J., 148, 117 (2014)>
=2014AJ....148..117J 2014AJ....148..117J (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, spectra ; Photometry, HST ;
Velocity dispersion ; Redshifts
Keywords: galaxies: clusters: individual: RXJ0848.6+4453 -
galaxies: evolution - galaxies: stellar content
Abstract:
RX J0848.6+4453 (Lynx W) at redshift 1.27 is part of the Lynx
Supercluster of galaxies. We present an analysis of the stellar
populations and star formation history for a sample of 24 members of
the cluster. Our study is based on deep optical spectroscopy obtained
with Gemini North combined with imaging data from Hubble Space
Telescope. Focusing on the 13 bulge-dominated galaxies for which we
can determine central velocity dispersions, we find that these show a
smaller evolution with redshift of sizes and velocity dispersions than
reported for field galaxies and galaxies in poorer clusters. Our data
show that the galaxies in RX J0848.6+4453 populate the fundamental
plane (FP) similar to that found for lower-redshift clusters. The
zero-point offset for the FP is smaller than expected if the cluster's
galaxies are to evolve passively through the location of the FP we
established in our previous work for z=0.8-0.9 cluster galaxies and
then to the present-day FP. The FP zero point for RXJ0848.6+4453
corresponds to an epoch of last star formation at
zform=1.95-0.15+0.22. Further, we find that the spectra of the
galaxies in RXJ0848.6+4453 are dominated by young stellar populations
at all galaxy masses and in many cases show emission indicating
low-level ongoing star formation. The average age of the young stellar
populations as estimated from the strength of the high-order Balmer
line Hζ is consistent with a major star formation episode 1-2Gyr
prior, which in turn agrees with zform=1.95. These galaxies
dominated by young stellar populations are distributed throughout the
cluster. We speculate that low-level star formation has not yet been
fully quenched in the center of this cluster, possibly because the
cluster is significantly poorer than other clusters previously studied
at similar redshifts, which appear to have very little ongoing star
formation in their centers. The mixture in RXJ0848.6+4453 of passive
galaxies with young stellar populations and massive galaxies still
experiencing some star formation appears similar to the galaxy
populations recently identified in two z~2 clusters.
Description:
Ground-based imaging of RX J0848.6+4453 was obtained primarily to show
the performance gain provided by replacing the original E2V
charge-coupled devices (E2V CCDs) in Gemini Multi-Object Spectrograph
on Gemini North (GMOS-N) with E2V Deep Depletion CCDs (E2V DD CCDs).
This replacement was done in 2011 October. Imaging of RX J0848.6+4453
was obtained with the original E2V CCDs in 2011 October (UT 2011 Oct 1
to 2011 Oct 2; Program ID: GN-2011B-DD-3) and repeated with the E2V DD
CCDs in 2011 November. The imaging was done in the z' filter. For the
observations with the original E2V CCDs the total exposure time was 60
minutes (obtained as 12 five-minute exposures) and the co-added image
had an image quality of FWHM=0.52'' measured from point sources in the
field. For the E2V DD CCDs a total exposure time of 55 minutes was
obtained and the resulting image quality was FWHM=0.51''.
Imaging of RX J0848.6+4453 was also obtained with Hubble Space
Telescope /Advanced Camera for Surveys (HST/ACS using the filters
F775W and F850LP) under the program ID 9919.
The spectroscopic observations were obtained in multi-object
spectroscopic (MOS) mode with GMOS-N (UT 2011 Nov 24 to 2012 Jan 4,
Program ID: GN-2011B-DD-5; UT 2013 Mar 9 to 2013 May 18, Program ID:
GN-2013A-Q-65).
Table10 lists the photometric parameters for the spectroscopic sample
as derived from the HST/ACS observations in F850LP and F775W.
Tables 11 and 12 list the results from the template fitting and the
derived line strengths, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table10.dat 82 54 RX J0848.6+4453: photometric parameters from
HST/ACS data
table11.dat 55 54 RX J0848.6+4453: results from template fitting
table12.dat 73 23 RX J0848.6+4453: line indices and [OII] for
cluster members
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See also:
I/252 : The USNO-A2.0 Catalogue (Monet+ 1998)
J/AJ/145/77 : Im. and spectroscopy in 3 galaxy clusters (Jorgensen+, 2013)
J/ApJS/184/271 : Photometry of galaxies in 3 clusters (Chiboucas+, 2009)
J/A+AS/139/29 : Empirical calibration of the 4000 A break (Gorgas+, 1999)
J/MNRAS/276/1341 : Spectroscopy of E and S0 galaxies (Jorgensen+, 1995)
J/MNRAS/273/1097 : CCD photometry for E and S0 galaxies (Jorgensen+ 1995)
Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Galaxy [240/9001] Galaxy identifier
6- 7 I2 h RAh Hour of Right Ascension (J2000) (1)
9- 10 I2 min RAm Minute of Right Ascension (J2000) (1)
12- 16 F5.2 s RAs Second of Right Ascension (J2000) (1)
18- 19 I2 deg DEd Degree of Declination (J2000) (1)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000) (1)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
29- 33 F5.2 mag z.SEx [21.2/24.89] Total HST/ACS F850LP magnitude from
SExtractor (mtot,SEx) (2)
35- 39 F5.3 mag i-z [0.018/1.075] Aperture HST/ACS F775W-F850LP
color index within an aperture with radius
0.5'' (i775-z850) (2)
41- 45 F5.2 mag z.dev [20.76/24.86]? Total HST/ACS F850LP magnitude
from fit with r1/4 profile (mtot,dev) (2)
47- 52 F6.3 [arcsec] r.dev [-1.125/0.392]? Logarithm of the effective
radius in arcsec from fit with r1/4 profile
(log re,dev) (3)
54- 58 F5.2 mag z.ser [21.05/24.88]? Total HST/ACS F850LP magnitude
from a fit with a Sersic profile
(mtot,ser) (2)
60- 65 F6.3 [arcsec] r.ser [-1.11/0.324]? Logarithm of the effective radius
from a fit with a Sersic profile
(log re,ser) (3)
67 A1 --- l_n [>] Lower limit flag on n
68- 70 F3.1 --- n [0.3/9.1] Sersic index (nser) (4)
71 A1 --- f_n [a] Flag 'a' means that no reliable Sersic fit
can be derived owing to scattered light from
a nearby source
73- 77 F5.1 deg PA [-90/90] Position angle of major axis measured
from north through east
79- 82 F4.2 --- Ell [0.05/0.84] Ellipticity ε
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Note (1): Positions consistent with USNO (Monet et al. 1998, Cat. I/252), with
an rms scatter of ∼0.5''.
Note (2): The photometry is calibrated to the AB system using the synthetic zero
points for the filters, 25.654 for for F775W, 24.862 for F850LP (Sirianni
et al. 2005PASP..117.1049S 2005PASP..117.1049S). The photometry was calibrated to rest-frame B
band. The calibration was established using stellar population models from
Bruzual & Charlot (2003MNRAS.344.1000B 2003MNRAS.344.1000B) as described in Jorgensen et al.
(2005AJ....129.1249J 2005AJ....129.1249J).
Note (3): The effective radii are derived from the semimajor and semiminor axes
as re=(aebe)1/2. The difference between the effective radii from
fits with an r1/4 profile and a Sersic profile should not be interpreted
as the uncertainty. As expected, the difference is correlated with the
Sersic index (see Figure 15 in the paper).
Note (4): With typical uncertainty of 0.1, while the uncertainties for Galaxy
2015 and 2111 are 0.7.
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Byte-by-byte Description of file: table11.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Galaxy [240/9001] Galaxy identifier
6- 11 F6.4 --- z [0.43/1.33]? Spectroscopic redshift
13 I1 --- Mm [0/2] Adopted membership (1=galaxy is a
member of the cluster, 0=galaxy is not a
member, or 2=no redshift) (5)
15- 19 F5.3 [km/s] sigma1 [1.975/2.631]? Log of velocity dispersion
(logσ)
21- 25 F5.3 [km/s] sigma2 [2/2.651]? Log of corrected velocity
dispersion (logσcor) (7)
27- 31 F5.3 [km/s] e_sigma1 [0.04/0.21]? Uncertainty on the velocity
dispersion (σlogσ) (6)
33- 36 F4.2 --- B8V [0/1]? Fraction of the template star of
spectral type B8V in the spectra (8)
38- 41 F4.2 --- G1V [0/1]? Fraction of the template star of
spectral type G1V in the spectra (8)
43- 46 F4.2 --- K0III [0/1]? Fraction of the template star of
spectral type K0III in the spectra (8)
48- 50 F3.1 --- chi2 [0.8/7.8]? Χ2
52- 55 F4.1 --- S/N [2.6/61.8] Signal-to-noise ratio per Å in
the rest frame of the galaxy (9)
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Note (5): The membership codes are fully defined as below:
0 = Galaxy is not a member of RX J0848.6+4453;
1 = Galaxy is a member of RX J0848.6+4453;
2 = Redshift cannot be determined.
Note (7): Velocity dispersion corrected to a standard size aperture equivalent
to a circular aperture with diameter of 3.4'' at the distance of the Coma
Cluster.
Note (6): Derived by the fitting software using a bootstrap method.
Note (8): The redshifts and velocity dispersions were determined by fitting the
spectra with a mix of three template stars (spectral types K0III, G1V, and
B8V) using software made available by Karl Gebhardt (Gebhardt et al.
2000AJ....119.1157G 2000AJ....119.1157G, 2003ApJ...597..239G 2003ApJ...597..239G). The galaxies that were found to
be members of the cluster were fit in the wavelength range 3750-4100Å.
Note (9): Wavelength interval was chosen based on the redshift of the galaxy:
Redshift 1.00-1.35: 3750-4100Å;
Redshift 0.60-1.00: 4100-4600Å;
Redshift less than 0.60: 4600-5200Å.
For Galaxy 336 and Galaxy 2624 a redshift of 1.27 was assumed for the S/N
calculation.
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Byte-by-byte Description of file: table12.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Galaxy [240/3090] Galaxy identifier
6- 10 F5.3 0.1nm CN3883 [0.07/0.202]? The CN3883 absorption-line
index; in Å (1)
12- 16 F5.3 0.1nm e_CN3883 [0.005/0.03]? Uncertainty in CN3883
(σCN3883); in Å
18- 22 F5.2 0.1nm CaHK [11.4/27.7]? The CaHK absorption-line
index; in Å (1)
24- 27 F4.2 0.1nm e_CaHK [0.27/1.63]? Uncertainty in CaHK
(σCaHK); in Å
29- 33 F5.3 0.1nm D4000 [1.544/3.154]? The D4000 absorption-line
index (measured as D4000short;
cf. Eq. (B2) in the text); in Å (1)
35- 39 F5.3 0.1nm e_D4000 [0.006/0.042]? Uncertainty in D4000
(σD4000); in Å
41- 45 F5.2 0.1nm HzA [1.99/12.68]? The HζA Balmer
absorption-line index; in Å (1)
47- 50 F4.2 0.1nm e_HzA [0.14/0.62]? Uncertainty in HzA
(σHζA); in Å
52- 56 F5.1 0.1nm EWOII [1.9/183.5]? [OII] equivalent width;
in Å
58- 62 F5.1 0.1nm e_EWOII [0.3/123.5]? Uncertainty in EWOII
(σEW[OII]); in Å
64- 68 F5.2 10-17W/m2/nm F[OII] [0.57/10.29]? Relative [OII] flux measured
within the spectral aperture (in units of
10-15erg/cm2/s/Å)
70- 73 F4.2 10-17W/m2/nm e_F[OII] [0.11/0.4]? Uncertainty in Flux
σflux([OII])
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Note (1): The indices have been corrected for galaxy velocity dispersion and
aperture corrected. The indices CN3883 and CaHK are defined in Davidge &
Clark (1994AJ....107..946D 1994AJ....107..946D). For D4000 we use a shorter red passband than
usually used (Gorgas et al. 1999, Cat. J/A+AS/139/29) but calibrate our
measurements to be consistent with the conventional definition of the
index; see Appendix for details. For the high-order Balmer line index
HζA we adopt the definition from Nantais et al. (2013A&A...556A.112N 2013A&A...556A.112N).
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(End) Sylvain Guehenneux [CDS] 05-Jan-2017