Star Forming Compact Groups (SFCGs): An ultraviolet search for a local sample

Transcription

1 Star Forming Compact Groups (SFCGs): An ultraviolet search for a local sample (2015, MNRAS, 453, 1965) Jonathan D. Hernández Fernández S-PLUS warn-up meeting August 11th 2016 São Paulo (Brazil)

2 The BLUE INFALLING GROUP is a compact group of galaxies infalling into the dynamically young cluster Abell 1367 BIG is the region with the highest density of star forming systems ever observed in the Local Universe (Cortese et al 2006). Hα GALEX SDSS coloured

3 The preprocessing scenario and the Blue Infalling Group (BIG). The unique case in the local Universe attributes to the preprocessing scenario is the BIG. A significant mechanism of star formation quenching in clusters. Infalling groups seem to be a possible place where spiral galaxies are becoming lenticulars (Haines+2013)

4 The BLUE INFALLING GROUP is a compact group of galaxies infalling into the dynamically young cluster Abell 1367 BIG is the region with the highest density of star forming systems ever observed in the Local Universe (Cortese et al 2006). Hα GALEX SDSS coloured GALEX catalogues are the place to search for this kind of groups...

5 SEARCH STRATREGY (1) Compilation of an all sky sample of UV bright sources (2) Search for groups in the UV sample

6 (1) Compilation of an all sky sample of UV bright sources UV sources from All-sky Imaging Survey (AIS) the largest sky area covered by GALEX in a homogeneous way

7 (1) Compilation of an all sky sample of UV bright sources UV sources from All-sky Imaging Survey (AIS) the largest sky area covered by GALEX in a homogeneous way FUV (1530 A) selection: 17 < FUV < 20.5 FUV is even more biased toward star-formation than the NUV. The brightest UV galaxies in BIG are approx. in this range lower limit: Avoiding bright galaxies which photometry shredded in parts. upper limit: Reliable sources, avoiding oversize the sample of UV sources.

8 (1) Compilation of an all sky sample of UV bright sources UV sources from All-sky Imaging Survey (AIS) the largest sky area covered by GALEX in a homogeneous way FUV (1530 A) selection: 17 < FUV < 20.5 FUV is even more biased toward star-formation than the NUV. The brightest UV galaxies in BIG are approx. in this range lower limit: Avoiding bright galaxies which photometry shredded in parts. upper limit: Reliable sources, avoiding oversize the sample of UV sources. UV color selection: < (FUV-NUV)dered < 2.75 Avoiding blue artifacts, red stars, etc.

9 (1) Compilation of an all sky sample of UV bright sources UV sources from All-sky Imaging Survey (AIS) the largest sky area covered by GALEX in a homogeneous way FUV (1530 A) selection: 17 < FUV < 20.5 FUV is even more biased toward star-formation than the NUV. The brightest UV galaxies in BIG are approx. in this range lower limit: Avoiding bright galaxies which photometry shredded in parts. upper limit: Reliable sources, avoiding oversize the sample of UV sources. UV color selection: < (FUV-NUV)dered < 2.75 Avoiding blue artifacts, red stars, etc. nuv_artifact <=1 good quality detections We avoid the Milky Way disk: galactic latitude modulus b >15º

10 (1) Compilation of an all sky sample of UV bright sources UV sources from All-sky Imaging Survey (AIS) the largest sky area covered by GALEX in a homogeneous way FUV (1530 A) selection: 17 < FUV < 20.5 FUV is even more biased toward star-formation than the NUV. The brightest UV galaxies in BIG are approx. in this range lower limit: Avoiding bright galaxies which photometry shredded in parts. upper limit: Reliable sources, avoiding oversize the sample of UV sources. UV color selection: < (FUV-NUV)dered < 2.75 Avoiding blue artifacts, red stars, etc. nuv_artifact <=1 good quality detections We avoid the Milky Way disk: galactic latitude modulus b >15º 925,428 UV-emitting sources

11 (2) Search for groups in the UV sample Friends-of-Friends Algorithm applied to sky positions grouping elements with a sky separation equal or less than a linklength = 1.5 arcmin This corresponds to a physical distance of 88 kpc at z=0.05

12 (2) Search for groups in the UV sample Friends-of-Friends Algorithm applied to sky positions grouping elements with a sky separation equal or less than a linklength = 1.5 arcmin This corresponds to a physical distance of 88 kpc at z=0.05 nuv >= 4 UV brigth members

13 (2) Search for groups in the UV sample Friends-of-Friends Algorithm applied to sky positions grouping elements with a sky separation equal or less than a linklength = 1.5 arcmin This corresponds to a physical distance of 88 kpc at z=0.05 nuv >= 4 UV brigth members Constraints over UV group members: At least three UV brigth sources classified as 'galaxy' by NED At least two galaxies with a redshift separation Δz<0.004

14 This final output of the search is a sample of groups of UV-emitting galaxies!!

15 This final output of the search is a sample of groups of UV-emitting galaxies!! nuv UV richness distribution: 226 groups with 4 members, 39 groups with 5 members, 11 groups with 6 members and 4 groups with 7 members Ngroups(nUV) ~ (nuv)α with α 7.53

16 One example of the groups that we found...

17

18 SFCGs close to clusters There are around 26 SFCGs embedded in the infalling regions of clusters with known redshifts. infalling regions: light blue areas

19 Our initial motivation was the search for similar examples to the BIG We have also a sample of compact groups What are the average group properties in comparison with other compact group samples?

20 Comparison with other samples of compact groups Hickson compact group sample (Hickson 1982, Hickson et al. 1992) SDSS compact group sample (McConnachie et al. 2005) 2MASS compact group sample (Diaz Gimenez et al. 2002)

21 FUV - NUV 2 3

22 Luminous star forming late type galaxies FUV - NUV 2 3

23 Luminous star forming late type galaxies -1 0 Passive early type galaxies 1 FUV - NUV 2 3

24 Star Forming fraction Sample SFing fraction SFCG 96 HCG 19 2MCG 13 SCG 20

25 dyn. time scale Dynamical (evolutionary) stage vel. dispersion

26 Dynamical (evolutionary) stage Earlier evol. stage dyn. time scale SCG 2MCG SFCG HCG vel. dispersion Later evol. stage

27 Earlier evol. stage SCG 2MCG SFCG HCG Later evol. stage

28 SFCG properties Low velocity disp. σlos ~ 120 kms 1 ~ small time scales tc ~ 0.7 Gyr High SFing fraction fsf ~ 95 % Dyn. masses ~ 3.4x1012M

29 ~ RESULTS ~ Compilation of a sample of 280 candidates to SFCGs Distinct properties from the group samples studied up now (optically and NIR selected) σlos ~ 120 kms 1, tc ~ 0.7 Gyr fsf ~ 95 %, Mdyn~ 3.4x1012 M 26 SFCG candidates infalling to clusters

30 ~ Lines of ongoing work ~ Only a 57 % of galaxy candidates to being group members have a redshift counterpart > It is required a REDSHIFT SURVEY: What of them are real groups? SFCG show a very high fraction of SFing galaxies > Level of star formation activity: H ALPHA SURVEY origin of this star formation activity? a different evolutionary stage?

31 ~ Spectroscopic survey ~ 34 groups asked to be observed in the Poor Weather mode in GMOS A long term project (6 semesters) in the SOAR Goodman spectrograph

32 ~ Spectroscopic survey ~ We have derived z's from 6 groups from observations w/ SOAR Goodman (only 3 nights)

33 ~ H alpha survey ~ 10 groups have been observed in the 2.2m CAHA telecope (Spain) r' band for the continuum and 3 NB filters at λ = 667, 678, 683 μm for capturing the z ed H alpha emission

34 SFCG002

35 SFCG009

36 SFCG012

37 SFCG168

38 SFCG174

39 SFCG181

40 SFCG182

41 SFCG197

42 SFCG224

43 SFCG280

44

45 SFCG012

46

47

48 Current status of the project Spectroscopic survey z's for 6 groups observed w/ SOAR Goodman Long term project at SOAR Goodman 34 groups to be observed w/ GMOS South H alpha survey 10 SFCG observed in Halpha CAHA 2.2m

49 What can we do with S-PLUS? Observation of SFCGs below z=0.02 Analysis of the underlying stellar population of galaxies in SFCGs

50 What can we do with S-PLUS? Observation of SFCGs below z=0.02 Analysis of the underlying stellar population of galaxies in SFCGs There are only nine groups with z<0.02 that can be observed below Dec=+10 SFCG008 SFCG065 SFCG198 SFCG045 SFCG109 SFCG223 SFCG060 SFCG145 SFCG253

51 Sky distribution of Southern SFCGs

52 What can we do with S-PLUS? Observation of SFCGs infalling to Southern clusters It takes advantage of the size of field of view because it includes the parent clusters.

53 What can we do with S-PLUS? Observation of SFCGs infalling to Southern clusters It takes advantage of the size of field of view because it includes the parent clusters. CLUSTER RA Dec z isfcg ABELL :04: :58: SFCG024 EDCC129 22:18: :49: SFCG199 EDCC155 22:32: :33: SFCG204

54 BACKUPS

55 SFCG232 SOAR SAM imager (Chile)

56 Stripped dwarf in SFCG232