Astronomy and Coffee

Galaxy Growth in a Dark Universe

This is the text I wrote during and after the conference in Heidelberg about the whole trip!

Day 0

Sunday 15.07, trip day to Heidelberg.

I really like to work on the ICE ... don't know if it the fact of being around 200-300 km/h, or if it's the fear or getting bored during the trip, so I take data, to reduce, papers to read, text to write ... probably it's the fear hehehehe

So, up to know astrometry of the already reduced filters for one of the clusters done. Now, gotta reduce WFI data (hate MEF data) and PUT WCS info on it, since this data set don't have it. Let's see, since the train has a delay of 25 min, maybe I'll have time for that.

Also was trying to make p2pp from ESO to work on the laptop, but there are problems with the JAVA ... why am I not surprised that it doesn't work as easy as it should?? Or that the troubleshooting don't have any info about "java problems"??? Or that the installation part of the manual limits itself to say "follow the webpage instructions step by step" ...

Jumping to "after Heidelberg" now!

The first part was written in the train going to Heidelberg and this part is being written in the train back from the conference.

It was a nice conference, very similar, in topics and participants, to the one in Marseille in 2005.

The time to the conference was also used to make p2pp (ESO phase 2 tool) work properly in the laptop, learn how it goes (reading the manual) and reading the instrument manual (mostly read in the train back :-) ). It's always like this, you'll never learn something new in a "stable" mode, I'm learning about IFU observations (never did that before, actually barely did spectroscopy) during a conference and rushing because the deadline for sending the phase II is in two weeks, but the collaborators that are the expert in the topic will be mostly out in those 2 weeks ... that means as much work as possible during this weekend!

About the conference was large and broad.

The first topic was "Formation and Structure of DM halos". First Mo gave us a complete vision on the structures and formation of the halos from a more theoretical point of view. Then Hildebrandt told us a bit about clustering of LBGs detected with U and B dropouts. Ferreras told us about mapping DM with lensing and to finish, McKean and Metcalf probed substructures in halos with lensing.

Then "Assembly of stellar mass". van Dokkum told us about stellar mass at high-z probing mass evolution with photometric z's and population synthesis and the in next step it will be possible to separate contribution of mergers and star formation. Grazian showed with GOODS-MUSIC that the red sequence is already in place at z ~ 3, at z ~ 2 50% of the red galaxies is already passive and at z between 2 and 3 the passive evolving galaxies have negative evolution. Cassata, using GMASS showed that passive old ellipticals at z 1.3-2 are smaller and denser than the local ones. Kriek talked about NIR spectral fit in massive galaxies at z ~ 2.5, showing suppressed star formation at 2.3. Kodama, using Subaru WF optical-NIR data showed the existence of the red sequence, already in z ~ 2, but not in z ~ 3, in contradiction with Grazian's talk. Mannucci showed strong evolution of the mass-metallicity relation at z > 3.

In a review talk, Bell talked about stellar mass assembly in the last 8 Gyr. Suggested that using masses instead of luminosities is "better" but has many assumptions. Stellar masses can be determined in a 0.1 dex accuracy and if wrong, is always overestimated. Mergers are enough to populate the red sequence, which has a growth in z < 1, by quenching and/or truncation of star formation (not subtle effects). Tanaka showed the build up of the red sequence at z < 1.3 with multi-band Subaru WF data and to close the first day van der Marel talked about the evolution of M/L of elliptical galaxies using fundamental plane and dynamical models at intermediate z. M/L and FP evolution agree, what would require the evolution of some other quantity involved.

In the second day, on "Assembly of Mass in Galaxies", Foerster-Schreiber talked about SINS, the high-z imaging survey in NIR with SINFONI. They have spatially resolved velocity fields at z ~ 2-3. A population of gas rich rotating disks at z ~ 2 was identified and mergers are probably needed to explain the observed features with the early formation of spheroids in this way. The barionic mass dominates in the center and the star formation obeys well a Schmidt-Kennicutt law. Haeusser talked about the use of GEMS to explore the formation of elliptical galaxies. He fitted Sersic profiles to the objects and raises the question that the separation at n <> 2.5 (where n is the Sersic index) to separate disks from ellipticals can be false. The high mass dense blue ellipticals would evolve to red ellipticals, while the low mass dense blue ellipticals would evolve back to disks or bulges, since they would need to get brighter to get to the red sequence.

Kassin talked about probing the galaxy and dark halo evolution to z ~ 1 with kinematics where instead of using the Tully-Fisher relation, which shows a quite large spread, she applies a kinematic indicator (Binney and Tremaine) that combines rotation and velocity dispersion and show a much tighter relation with mass than the T-F. That topic raised some debate on the real meaning of this relation. Scodeggio gave us the update on the VVDS deep, showing that downsizing is significant at 0.5 < z < 1.3 and that the mass function agrees with the star formation history. To finish this section Perez-Gonzales talked about the Spitzer view of the mass assembly of galaxies where 50% of the stars formed before z ~ 1 and more than of it formed after z ~ 4. Downsizing is present and there's a mismatch between star formation rate and stellar mass density evolution. This may be contamination by AGN's at high-z of evolution of the IMF and/or the SFR.

In "History of Star Formation: low z" Papovich talked about the history of SF since z ~ 1 with two questions: "when did the stellar population in massive galaxies assemble" and "when did (and how) the galaxies formed their stars". For the first, in galaxies more massive than 10^11 M_sun, 80% of the stars assemble by z ~ 0.3, the spatial density of 4 L* red galaxies is unchanged since z ~ 0.9 and the number density of > 10^11 M_sun red galaxies is unchanged since z ~ 0.8. For the second question, models don't predict the spatial density of galaxies with SFR > 50 (0.2 < z < 2.5), they over-restrict SF at z < 3. The interpretation of the models can be inaccurate or the transformation of IR luminosity to SFR can be inaccurate. Due to the fact that the IFU project co-I's needed to discuss the preparation of the next run, which I'm in charge, I couldn't be at Juneau's talk about Spitzer identified galaxies at 0.4 < z < 1.0 and Takeuchi's about visible and hidden SF at 0 < z < 1 and also to the whole "The role of Barions in Galaxy Formation" section with talks from Sommerville, Katz, Crain, Koeckert, Rothberg and Dave. By the abstract I could see that Rothberg's semi-analytic models of globular cluster formation can account for the bimodality with reionization at z ~ 7-8 (consistent with WMAP) and not at z ~ 5, as previous models needed. That topic personally calls my attention, since I "come" from the globular clusters community, too bad I couldn't see his talk.

Third day was the short one (free afternoon and conference dinner) with "The History of Star Formation at High z". Illingworth talked about the galaxy build up from z ~ 10 to z ~ 3, showing the increase of u-dropouts in the last years. The luminosity function of z = 4, 5 and 6 show evolution with fainter bright ends and the faint ends are compatible with alpha ~ -1.75 and not -1.3. Now the search is for J-dropouts (z ~ 10) where gravitational telescopes can be an option but they are not showing good results. Pirzkal talked about star formation galaxies at 4.7 <> 6 show evolution indicating less dust extinction and even though 8 J-dropouts would be expected in the observed area, assuming no evolution from z ~ 6 and 2 assuming no evolution from z ~ 7-8, none was detected. Couldn't really be "into" the talks from Huang, Tasitsiomi, Gawiser, Bouche, Damen and Maier, for the same reason as the day before.

After the conference dinner it was hard to get on time for Volonteri's talk on "Early growth of super-massive black holes", but I made on time, for van den Bosch's talk on galaxy ecology, opening the "Role of Environment" section, where he reviewed the environment dependent processes to which galaxies are submitted to (tidal stripping and heating, strangulation, ram pressure and harassment), and the concepts that SF decreases with density (Balogh), Specific SF decreases with density (Kaufman) and color is not correlated with density, but with "morphology" (Hogg). According to him we should use physical parameters as virial radius and virial mass to correctly access the physics of the environment and not densities of centric distances. In groups they used masses estimated from the total luminous mass and not from velocity dispersions (which can have a poor meaning due to the small number of members) and compared the properties between "centrals" and "satellites", where satellites are redder than centrals (for a given mass) and that would be an environmental effect, a mass segregation. Massive galaxies are transformed as centrals and low mass as satellites and the efficiency in the transformation independs of the halo mass. The satellites show no environmental dependences, only with stellar mass and any environmental dependence vanishes when separating centrals from satellites (for a given mass). Something to "digest".

Brown talked about red galaxies growth in the NDWFS Bootes field, where there's some assembly of 4L* red galaxies at z <> 10^12 M_sun satellites are red, isolated galaxies show no faint, red centrals and that in groups and clusters the fraction of late-type galaxies depend on halo mass for both, centrals and satellites. Recalled the "faint red galaxies problem" (Weinmann et al) and say that this can come from the fact that the "field" is dominated by groups. Solutions for this problem would be a Mass threshold (10^13-14 is good for clusters) or a timescale problem. For mass threshold, groups on CNOC2, at z ~ 0.5 have masses of 10^13-14, while the Millenium run had most of the haloes at 10^11. For timescale, strangulation could be the mechanism with a delay in gas stripping and the actual strangulation of SF. So that environmental effects would influence galaxy formation after z ~ 1, those effects would be dominating in massive groups, not in clusters and environmental effect in models would be wrong because the field is dominated by groups. Jones talked about the 6DF survey, nice perspectives for LSS and galaxy evolution and Pollo closed the morning with luminosity dependent clustering in the VVDS.

In the afternoon Mei talked about tracing galaxy evolution in clusters and groups at z > 1, Blindert gave us some results for the Red Sequence Cluster Survey, where they found 33 clusters with masses 10^13-15, 10-100 members and about 12% of contamination, now they are going for spectroscopy, but it doesn't cover yet a large centric distance. Zatloukal talked about high-z clusters in COSMOS detected with HIROCS, where 12 clusters at z > 1.2 where detected. Ziegler (I'm suspect to talk about those projects, since he's my boss and I'm involved directly or indirectly on them) talked about kinematic evolution of field and cluster spirals. The first part is the evolution of the T-F relation between 0.1 < z < 1.0, in the field, while the M/L don't evolve, the second part where the environmental effects are studied in 6 clusters and nice results are being found and to close, the combination of studying velocity fields and high-resolution images of galaxies in clusters at z ~ 0.5, which will give the T-F relation with high accuracy at this distance. To finish the section Wolf spoke about the complex cluster A901/902 studied with COMBO-17. After that I had to leave to keep on my IFU duties and only came back for the best poster prize, three very good posters got it and to the conference summary. About posters in this conference there was some good work there, I looked at all of them, looked carefully at some of them, but they were mostly "forgotten" during the whole time. It would have been interesting to do some poster advertisement, or at least that each sections chair made an effort for the people to break for coffee in front of them and not outside of the room ...

Anyway, the conference was very nice! Now prepare material for the next one!

posted by Cris Da Rocha @ 12:16 PM