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Deep infrared inaeiug survevs (e. Djorgovski et al.
Deep infrared imaging surveys (e.g., Djorgovski et al.
1995) have shown that iu he A baud (2.2 jun). on average. there are 2 galaxies xiehter than A = 20 mae within 20” of auy star.
1995) have shown that in the $K$ band (2.2 $\mu$ m), on average, there are 2 galaxies brighter than $K$ = 20 mag within $20''$ of any star.
These objects form: a statistically unbiased set of galaxics at eh redshift and provide an excelleut sample for stucdving ealaxy evolution.
These objects form a statistically unbiased set of galaxies at high redshift and provide an excellent sample for studying galaxy evolution.
At a typical redshift between 0.25 aud 1.0 (corresponding to look back times of «109. vears ago) these objects are seen at a critical time in galaxyvelopiueut?.
At a typical redshift between 0.25 and 1.0 (corresponding to look back times of $\times$ $^9$ years ago) these objects are seen at a critical time in galaxy.
. This correspouds to just after the time that the Milkv Was disk appears to have stabilized and when the oldest disk stars formed (Winget et al.
This corresponds to just after the time that the Milky Way's disk appears to have stabilized and when the oldest disk stars formed (Winget et al.
1987).
1987).
Receut evidence also indicates that star formation throughout the Universe nav have begun its decline to the present levels at around 2=1 (Madau. Pozzetti. Dickiusou 1998).
Recent evidence also indicates that star formation throughout the Universe may have begun its decline to the present levels at around $z=1$ (Madau, Pozzetti, Dickinson 1998).
Between 1998 September aud 1999 July. 25 stars were imaged with a non-AO infrared camera (NTIRC: Matthews Soifer 1991) on the Keck-T telescope.
Between 1998 September and 1999 July, 25 stars were imaged with a non-AO infrared camera (NIRC; Matthews Soifer 1994) on the Keck-I telescope.
These images were used to provide a sample of galaxies within 30 of potential guide stars.
These images were used to provide a sample of galaxies within $30''$ of potential guide stars.
The stars were all A-type stars with a visual magnitude between 8 aud 12.
The stars were all A-type stars with a visual magnitude between 8 and 12.
Over 200 ealaxics were selected ii these fields down to a A-band magnitude of 21.5.
Over 200 galaxies were selected in these fields down to a $K$ -band magnitude of 21.5.
\lauy of the fields also lave fiut off-axis stars that can be used to measure the PSF in order to determine the level of correction achieved.
Many of the fields also have faint off-axis stars that can be used to measure the PSF in order to determine the level of correction achieved.
This is critical since the performance of ΑΟ systems can vary significantly with position in the sky and brightuess of the enide star.
This is critical since the performance of AO systems can vary significantly with position in the sky and brightness of the guide star.
These pre-AO images are detailed in Larkin Classiman (1999).
These pre-AO images are detailed in Larkin Glassman (1999).
The camera used for the AO observations was NCAA which was developed at UCLA by James Larkin aud Tan MeLean in coordination with Peter Wizinowich aud the AO development team.
The camera used for the AO observations was KCAM, which was developed at UCLA by James Larkin and Ian McLean in coordination with Peter Wizinowich and the AO development team.
It uses a NICMOS infrared array detector with «256 pixel clemeuts.
It uses a NICMOS infrared array detector with $\times$ 256 pixel elements.
It is sensitive frou 1 to 2.5 jan. although the οποια filter set liit it to J (1.27 jiu). 11 (1.65 jn) and A’ (2.15 gam).
It is sensitive from 1 to 2.5 $\mu$ m, although the current filter set limit it to $J$ (1.27 $\mu$ m), $H$ (1.65 $\mu$ m) and $K^\prime$ (2.15 $\mu$ m).
The plate scale in theZf-baud is 070176 4 OYO00L per pixel viclding a total field of view of 1751 (Macintosh 2000).
The plate scale in the$H$ -band is $\farcs$ 0176 $\pm$ $\farcs$ 0004 per pixel yielding a total field of view of $\farcs$ 51 (Macintosh 2000).
This plate scale was selected to Nyquist sample the Z£-baud diffraction Imt.
This plate scale was selected to Nyquist sample the $H$ -band diffraction limit.
Ou 1999 April 3. we observed the first faint field ealaxy ever examined with a Shack-Tartinann AO svsteu.
On 1999 April 3, we observed the first faint field galaxy ever examined with a Shack-Hartmann AO system.
The ealaxy is 187 from a V—10.2 mag natural enide star (NGS) named PPM. 127095. 05726,865. |16*21'507118. J2000).
The galaxy is $''$ from a $V$ =10.2 mag natural guide star (NGS) named PPM 127095 $^h$ $^m$ $^s$, $^\circ$ $^\prime$ 18, J2000).
The galaxy (PPM is 19.0 mae iu the Z£-baud.
The galaxy (PPM is 19.0 mag in the $H$ -band.
Its infrared colors are J.—HI[50.9 nag and JFIK —0.8 nag.
Its infrared colors are $J-H$ =0.9 mag and $H-K$ =0.8 mag.
Nou-AO imagine uarginallv resolved the galaxy in good seciug conditions (0755). but no morphological information was available.
Non-AO imaging marginally resolved the galaxy in good seeing conditions 5), but no morphological information was available.
A second star 1779 frou the same NCS was used to measure he PSF.
A second star $\farcs$ 9 from the same NGS was used to measure the PSF.
Six exposures of five ninutes cach were taken ou he galaxy. with the PSF star observed before aud after he galaxy sequence.
Six exposures of five minutes each were taken on the galaxy, with the PSF star observed before and after the galaxy sequence.
Between cach of the six exposures. he galaxv was moved 2" ina square dither pattern.
Between each of the six exposures, the galaxy was moved $2''$ in a square dither pattern.
The otal integration time was limited by the demands of the AQ comuissioning ο.
The total integration time was limited by the demands of the AO commissioning program.
A second galaxy was observed in a similar iuanner in September 1999.
A second galaxy was observed in a similar manner in September 1999.
The ealaxy (PPM 11118216)27) is 27” away from the sth mag A-type star PPM 111182 =22713 10.2%, 21702/587 77. J2000) and has a total /T-baud magnitude of 17.1 and au extent of roughly 37,
The galaxy (PPM 114182+6+27) is $27''$ away from the 8th mag A-type star PPM 114182 $^h$ $^m$ $^s$, $^\circ$ $^\prime$ 7, J2000) and has a total $H$ -band magnitude of 17.4 and an extent of roughly $3''$.
Its infrared colors are J[720.2 mag aud JT.IK —0.1 mae.
Its infrared colors are $J-H$ =0.7 mag and $H-K$ =0.1 mag.
In this particular case. the Strehl ratio degraded rapidly durius the observations from ~0.2 to less than 70.1.
In this particular case, the Strehl ratio degraded rapidly during the observations from $\sim$ 0.2 to less than $\sim$ 0.1.
Iu the final ππασο, only the first three frames (each 5 niuutes) out of a total of six were utilized.
In the final image, only the first three frames (each 5 minutes) out of a total of six were utilized.
The variability of the PSF is discussed in the results section below.
The variability of the PSF is discussed in the results section below.
This ealaxy was also observed with the optical spectrograph LRIS (Oke et al.
This galaxy was also observed with the optical spectrograph LRIS (Oke et al.
1995) ou the IKeck-II telescope on 1999 December 12.
1995) on the Keck-II telescope on 1999 December 12.
Two I0-unute exposures were taken. but the first suffered from a large amount of scattered light from the PPM star and was not used.
Two 10-minute exposures were taken, but the first suffered from a large amount of scattered light from the PPM star and was not used.
The images were reduced using standard techniques for non-AO images.
The images were reduced using standard techniques for non-AO images.
Sky frames were created by masking off the quadrant with the galaxy from cach frame aud then they were medianed together without positional offset.
Sky frames were created by masking off the quadrant with the galaxy from each frame and then they were medianed together without positional offset.
For PPM 5210131. frames with poor Strelil ratios were used for creating median sky frames even if they weren't used for the final mage.
For PPM 114182+6+27, frames with poor Strehl ratios were used for creating median sky frames even if they weren't used for the final image.
Flat feld images were created from observations of the twilight sky.
Flat field images were created from observations of the twilight sky.
Figure l shows the mage of PPM. 127095-8|16.
Figure 1 shows the image of PPM 127095-8+16.
The contours of the ealaxy are consistent with a disk galaxy with au inchnation of 65°.
The contours of the galaxy are consistent with a disk galaxy with an inclination of $^\circ$ .
We removed the first-order effects of inclination by rotating the image. making its major axis horizontal. then resampling it iu the vertical direction to produce roughlv circular isophotes.
We removed the first-order effects of inclination by rotating the image, making its major axis horizontal, then resampling it in the vertical direction to produce roughly circular isophotes.
The
The
ocurs in à density range consistent with that found for the fraction of strong star-forming pairs.
ocurs in a density range consistent with that found for the fraction of strong star-forming pairs.
We have also explore the dependence of the fraction of extreme red. galaxies on projected separation and. relative velocity.
We have also explore the dependence of the fraction of extreme red galaxies on projected separation and relative velocity.
Fig.13. shows an equivalent set of plots to that of he extreme blue fraction displaved in Fig.11.. for the same range of X values.
\ref{colredrpV} shows an equivalent set of plots to that of the extreme blue fraction displayed in \ref{colrpV}, for the same range of $\Sigma$ values.
Note. that the fraction of red galaxies in he control samples are almost independent of environmen and their boostrap errors are z0.005.
Note, that the fraction of red galaxies in the control samples are almost independent of environment and their boostrap errors are $\approx 0.005$.
For galaxies in. pairs here is an increase of this fraction for small rj ancl AV values. indicating that close pairs have an excess of rec objects regardless of the environment.
For galaxies in pairs there is an increase of this fraction for small $r_{\rm p}$ and $\Delta V$ values, indicating that close pairs have an excess of red objects regardless of the environment.
The boostrap error xus for the fractions of the pair and control samples indicate hat the signae is statistically meaningful at more than 360-evel.
The boostrap error bars for the fractions of the pair and control samples indicate that the signal is statistically meaningful at more than $3\sigma$ -level.
One possible interpretation of this trend is that many ealaxies in pairs have been very. efficient in forming stars at carly stages of their evolution so that. currently. they exhibit red colours.
One possible interpretation of this trend is that many galaxies in pairs have been very efficient in forming stars at early stages of their evolution so that, currently, they exhibit red colours.
Llowever. from Fig.S we can appreciate that the fractions of low star-forming galaxies decrease for smaller relative separation for all environments. while the strong star-forming fractions increase (Lig.4)).
However, from \ref{SFRrpnonfor} we can appreciate that the fractions of low star-forming galaxies decrease for smaller relative separation for all environments, while the strong star-forming fractions increase \ref{SFRrp}) ).
The behaviour of colours ancl star formation activity suggests that there is an important fraction of galaxies in. very close pairs (ryDf+ kpe) which tend to be redder than the rest. of the ealaxies but have enhanced star formation activity with respect to the control sample.
The behaviour of colours and star formation activity suggests that there is an important fraction of galaxies in very close pairs $r_{\rm p} < 20 \kpc $ ) which tend to be redder than the rest of the galaxies but have enhanced star formation activity with respect to the control sample.
Ehe red colours of these star-forming galaxies in close pairs could be due to obscuration as the result of dust stirred. up during the encounter which could also hide part of the star formation activity.
The red colours of these star-forming galaxies in close pairs could be due to obscuration as the result of dust stirred up during the encounter which could also hide part of the star formation activity.
In order to further understand. the dependence. on environment. of the fraction. of galaxies with red. colour indexes in close pairs and in galaxies without a close companion. we have analysed the fraction of extreme red ealaxies in close pairs as a function of the local density parameter.
In order to further understand the dependence on environment of the fraction of galaxies with red colour indexes in close pairs and in galaxies without a close companion, we have analysed the fraction of extreme red galaxies in close pairs as a function of the local density parameter, $\Sigma$.
The results are shown in Fig.14. from where it can be appreciated that there is an excess of extreme red ealaxies in close pairs compared to that of the control sample in all kind. of environment.
The results are shown in \ref{colredSig} from where it can be appreciated that there is an excess of extreme red galaxies in close pairs compared to that of the control sample in all kind of environment.
This trend tends to be stronger in high density environments. consistent. with the results of low star-forming galaxies cliscussed in Section 3.
This trend tends to be stronger in high density environments, consistent with the results of low star-forming galaxies discussed in Section 3.
We also notice that at. extremely low density environments. galaxies regardless of the presence of a companion. also show a larger fraction of red objects in comparison with those of transition density. region.
We also notice that at, extremely low density environments, galaxies regardless of the presence of a companion, also show a larger fraction of red objects in comparison with those of transition density region.
This eature is consistent with the change in the slope of the relation between the fraction of low star-orming galaxies and X detected for fog Xx1.2 (Fig.9)).
This feature is consistent with the change in the slope of the relation between the fraction of low star-forming galaxies and $\Sigma$ detected for $log$ $\Sigma \le -1.2$ \ref{sfrbsigless}) ).
We argue that hese trends can be interpreted as the result of the growth of small scale overdensities in global underdense regions. where he subsequent infall of gas and as a consequence. the star ormation activity is likely to have been strongly reduced at ater times.
We argue that these trends can be interpreted as the result of the growth of small scale overdensities in global underdense regions, where the subsequent infall of gas and as a consequence, the star formation activity is likely to have been strongly reduced at later times.
Hence generally. galaxies would be less efficiently eeded by gas. infall in this regions. and on top of that. ealaxies in pairs would be more ellicient at consuming this eas. producing a Larger fraction of red and low star-forming svstcHis.
Hence generally, galaxies would be less efficiently feeded by gas infall in this regions, and on top of that, galaxies in pairs would be more efficient at consuming this gas, producing a larger fraction of red and low star-forming systems.
Previous studies of the colour distribution of galaxies showed an important. dependence of the fraction of. red. ealaxies with environment and luminosity (Ixaullbmann et al.
Previous studies of the colour distribution of galaxies showed an important dependence of the fraction of red galaxies with environment and luminosity (Kauffmann et al.
2004: Balogh et al.
2004; Balogh et al.
2004: Balelry ct al.
2004; Baldry et al.
2003).
2003).
In. particular. Balogh et al. (
In particular, Balogh et al. (
2004) claimed that the colour distribution is bimodal with only the relative fraction of galaxies in the red ancl bluc peaks varving with local density and luminosity.
2004) claimed that the colour distribution is bimodal with only the relative fraction of galaxies in the red and blue peaks varying with local density and luminosity.
These authors interpreted their results resorting
These authors interpreted their results resorting
Where p ds the mean density of the universe.
Where $\rho$ is the mean density of the universe.
This process continues for a sullicient number of iterations (seeSection 1.1). that the €Shave converged to near constant. values.
This process continues for a sufficient number of iterations (seeSection \ref{nitty}) ), that the $ C_{i,n}^{ \alpha} $ have converged to near constant values.
We will then know the orbit of every mass ane thus its »eculiar motion.
We will then know the orbit of every mass and thus its peculiar motion.
We place all of the available mass in the »oint masses and unlike previous papers (P90. 895). do not consider the possibility of a smooth component to the mass (which was found to have little effect on the results).
We place all of the available mass in the point masses and unlike previous papers (P90, S95), do not consider the possibility of a smooth component to the mass (which was found to have little effect on the results).
So [ar our discussion has been in terms of point masses.
So far our discussion has been in terms of point masses.
In reality. though. we will have to apply the Least. Action 'rinciple to à set of galaxies.
In reality, though, we will have to apply the Least Action Principle to a set of galaxies.
As a result we will have to make the assumption that all of the mass is concentrated in hese galaxies.
As a result we will have to make the assumption that all of the mass is concentrated in these galaxies.
An important consequence of this assumption is that we require the size of galaxy halo (or group halo. see Section 3.4)) to be less than the average distance between galaxies.
An important consequence of this assumption is that we require the size of galaxy halo (or group halo, see Section \ref{group}) ) to be less than the average distance between galaxies.
Phere is some support for this approximation from studies of the Local Ciroup.
There is some support for this approximation from studies of the Local Group.
Zaritsky et al (1989). apply the iming argument to the Milkv Wav- Leo I svstem and the Milky Way- MS system. and find roughly the same mass or the Local Group.
Zaritsky et al (1989), apply the timing argument to the Milky Way- Leo I system and the Milky Way- M31 system, and find roughly the same mass for the Local Group.
As Leo Lis at 200kpe ancl M31 is at TOOpe. this implies that the Milkv. Way does not have a arge extended. halo.
As Leo I is at $200kpc$ and M31 is at $700kpc$, this implies that the Milky Way does not have a large extended halo.
In addition. Peebles (1994.1995) finds hat it is possible to construct satisfactory orbits for Local eroup satellites anc nearby groups. with simple compact ialoes.
In addition, Peebles (1994,1995) finds that it is possible to construct satisfactory orbits for Local group satellites and nearby groups with simple compact haloes.
Another consequence of the assumption that all of he mass is concentrated in galaxies is to place limits on the distribution of loose mass in the Universe (bv. loose mass we mean mass which is not in haloes).
Another consequence of the assumption that all of the mass is concentrated in galaxies is to place limits on the distribution of loose mass in the Universe (by loose mass we mean mass which is not in haloes).
This is particularly important in CDM models where up to 50% of the mass can be loose in a (3;=1 universe ancl ereater proportions for lower density. universes (Ciovernato. private communication).
This is particularly important in CDM models where up to $50$ of the mass can be loose in a $ \Omega_{0}=1$ universe and greater proportions for lower density universes (Governato, private communication).
At the scale of the Local Croup. Branchini Calbere (1994) and Dunn Lallammoe (1995) have tested the Least Action Principle in CDM universes.
At the scale of the Local Group, Branchini Calberg (1994) and Dunn Laflamme (1995) have tested the Least Action Principle in CDM universes.
“Phe results from these tests are not totally reliable. as the simulations used had either. been rescalecdl lor use on Local Group. or. lacked resolution.
The results from these tests are not totally reliable, as the simulations used had either been rescaled for use on Local Group, or lacked resolution.
Both papers found a tendency for the Least Action Principle to under-predicetο
Both papers found a tendency for the Least Action Principle to under-predict.
ι, Dranchini Calberg attributed these problems to extended haloes. whereas Dunn Lallamme thought the problem was more to do with loose mass.
Branchini Calberg attributed these problems to extended haloes, whereas Dunn Laflamme thought the problem was more to do with loose mass.
Our analysis is at larger scales. so it is not clear what to expect in CDM models.
Our analysis is at larger scales, so it is not clear what to expect in CDM models.
The condition that the mass is concentrated at. the centre of the mass tracers has no chance of being satisfied at carly epochs.
The condition that the mass is concentrated at the centre of the mass tracers has no chance of being satisfied at early epochs.
The best we can hope for is that the perturbations are roughly spherical and centred. on. the mass tracers.
The best we can hope for is that the perturbations are roughly spherical and centred on the mass tracers.
We are. though. entirely concerned with the velocities of galaxies and these will be generated. mainly at late epochs.
We are, though, entirely concerned with the velocities of galaxies and these will be generated mainly at late epochs.
Thus the problems with the tracing of the density field at carly epochs should not be too serious.
Thus the problems with the tracing of the density field at early epochs should not be too serious.
1n this Section. we discuss the galaxy. catalogues to which we apply the Least Action Principle.
In this Section, we discuss the galaxy catalogues to which we apply the Least Action Principle.
However. raw galaxy catalogues in the form of a list of galaxy positions. recdshifts and Hux. are not suitable to have the Least Action Principle directly. applied. to them.
However, raw galaxy catalogues in the form of a list of galaxy positions, redshifts and flux, are not suitable to have the Least Action Principle directly applied to them.
For example. the raw redshifts will have a contribution both from the IIubble flow and the peculiar velocity of a galaxy. so will not be the true measure of distance we require.
For example, the raw redshifts will have a contribution both from the Hubble flow and the peculiar velocity of a galaxy, so will not be the true measure of distance we require.
Consequently. this Section will include not only a description of the galaxy catalogues we use. but also a description of the processes we apply to the galaxy catalogues. to make them suitable for calculations with the Least Action Principle.
Consequently, this Section will include not only a description of the galaxy catalogues we use, but also a description of the processes we apply to the galaxy catalogues, to make them suitable for calculations with the Least Action Principle.
For peculiar velocity. work. there will. be certain desirable properties we will want in a galaxy catalogue.
For peculiar velocity work, there will be certain desirable properties we will want in a galaxy catalogue.
The most important of these is that the catalogue is uniformly selected: across the sky. as preferential selection in any region. will result in false motions being calculated towards that region.
The most important of these is that the catalogue is uniformly selected across the sky, as preferential selection in any region, will result in false motions being calculated towards that region.
Another important property is that we want the catalogue to cover as great a fraction of the sky as possible.
Another important property is that we want the catalogue to cover as great a fraction of the sky as possible.
All catalogues will have an "excluded: region” or. "mask around the galactic plane.
All catalogues will have an “excluded region” or “mask” around the galactic plane.