Survey Area and observing progress

 The VVV Survey

The VVV   Survey covers ~ 528 deg² containing ∼10^9 point sources and it includes multi-wavelength (ZYJHKs) coverage of the area as well as time monitoring in Ks band. The survey is scheduled to collect over 2000 hours of execution time.

The VISTA Telescope tile field of view is 1.501 deg², hence 196 tiles are needed to map the bulge area and 152 tiles for the disk. Adding some X and Y overlap between tiles for a smooth match, the area of our unit tile covered twice is 1.458 deg².

The VVV bulge area covers −10º < l < +10º and −10º < b < +5º, where the survey will give the most complete catalogue of variable objects in the bulge, with more than ∼10^6 variables. Chief among them are the RR Lyrae, which are accurate primary distance indicators, and well understood regarding their chemical, pulsational and evolutionary properties. Our survey of the RR Lyrae in the Galactic bulge will allow us to map its 3-D structure (as shown by Carney et al., 1995) and will provide key information on the age of its population, given that RR Lyrae stars are tracers of the old population (e.g., Catelan, 2004b, 2009, …).

VVV Survey Area Tile Numbers
VVV Survey Area Tile Numbers – Galactic Coordinates

In order to understand the Milky Way’s populations globally, it is necessary to survey the inner Galactic plane as well. Therefore, we will survey an adjacent region of the mid-plane and provide a Legacy Database and 3-D atlas of a large Population I (i.e. young and luminous stars) region. We have selected the region −65º < l < −10º and |b| < 2º, where star-formation activity is high and for which there will be complementary optical, mid-IR, and far-IR data from VPHAS+, the Spitzer, GLIMPSE and MIPSGAL surveys, and from the all- sky AKARI and WISE survey.

The Ks- band observations

The variability study in the bulge will be carried out in the Ks band down to ∼18 mag (signal-to-noise ≈ 3). The total exposure time for a VISTA tile field is 162 s. Our strategy yields about 30 deg² per hour, or 300 deg² per night. The combined epochs will reach Ks = 20 mag, which is three magnitudes fainter than the de-reddened bulge main-sequence turn-off (MS turn-off), although the densest fields will be confusion-limited. However, applying both PSF fitting and image subtraction, we will recover the light curves of most objects down to Ks = 18 mag, even in moderately crowded fields. This is more than 3 mag fainter than the de-reddened known RR Lyrae in the Galactic bulge. We expect to find RR Lyrae even in fields with AV = 10 mag.

If you are interested in the distribution of the individual Ks-band epochs, have a look at the next two plots.

The VVV eXtension:  VVVX

The observations for VVVX commenced on June 30, 2016, and will continue until 2021.

VVVX was granted a total of 2000 hours observing time, covers a total of ~1700 sqr. degrees on sky and consists now of 1028 individual VIRCAM tiles.  In contrast to VVV the additional areas will be observed in J, H and Ks only.  The color coded areas shown in the figure below are:

I. Red: the original VVV area, for which we will obtain between 3 to 10 additional Ks-band observations, one to three per year, to extend the time line for PM studies.

II. Cyan: High/Low Bulge, extending the original bulge area to latitude +9.5º and -14.5º.

III. Green: Disk+20: extending the disk area from l=+10º to +20º, with b=-4.5º to +4.5º

IV. Blue: High/Low disk: extending the southern disk area from |b|=-2.28º to 4.5º. This will connect the VVV/VVVX area to the VISTA Hemisphere Survey, at least partially, given that VHS uses a RA/DEC alignment of the tiles, whereas VVV/VVVX is aligned along l,b. The longitude range for this area is l=230º to 350º. The combination of VVV/VVVX and the UKIDDS Galactic Plane survey will cover the entire galactic disk, over the full 360º longitude range!!!

V. Yellow: Disk+230: extend the inner galactic disk area (|b|<=2.28º) from l=295º to 230º.

The observations for areas II to V will include deep JHKs multi-color observations and multi-epoch observations in the Ks band, the exact number of epochs varying for the different area. Disk 230 will be observed in Ks 39 times (incl. the multi-color observation). Disk-low/high , Bulge-low/high, and Disk+20 will be observed 24 times in Ks, also incl. the multi-color observations.

vvvx_area
Color code for the area covered by the VVV eXtended; VVVX
New_VISTA_PS_Cy2
Sky coverage of Cycle 2 Public Surveys with VISTA ©ESO

Progress in observations

All observations scheduled for the original VVV survey have been completed in 2015.
Starting in P97  (June 2016) ESO also started observing for VVVX. The following plots show the number of COMPLETED Ks-band observations  (aka ACCEPTED by ESO as within observing constrains ) at the given date (see headline of plots).  The upper number in each field gives the tile ID, whereas the lower number gives the number of Ks-band epochs, and includes the Ks-band observations carried out within the multi-color OBs.
The first plot refers to the areas I (VVV bulge), II (low/high bulge) and III (disk+20).

The inner disk tiles (region I and IV) are shown in the next plot.

The most southern part of the disk area is shown in the last plot.

 In addition the disk+230 area and the outer ranges of the lower (dl) and upper disk (dh)  area have been observed as well, although first observations started only in P100.
The progress in observations is shown in the plots below. The different observing runs for VVV (run: 179.B-2002 A, B, C, D, E, F, G, H, K, L) and VVVX (run: 198.B-2004 A, B, C, D, E, F, H, J) were all completed. There are 4 VVVX run currently open- 179.B-2004 (G, I, K, L). Run 198.B-2004(C) as well as 100 hours of run 198.B-2004(G) were – like run 198.B-2004(A) an early submission to make use of observing time during P99 and P102 that could not be used by other projects, due to weather conditions. Run 198.B-2004(D) includes 150 h of observation of the outer southern disk, and is the first summer semester within the VVVX survey. The multi-color observations for the new areas in VVVX have all been completed by end of 2018. In fact as of April 2019 only observations of the summer targets (disk-230, outer areas of disk-low/high) have to be submitted. All the rest is already in the observing queue.

Completeness at 13.02.2020

198.B-2004(A): 2318 of 2318 OBs: 100.0%, or 202.6 of 202.6 h: 100.0%

198.B-2004(B): 1779 of 1779 OBs: 100.0%, or 212.1 of 212.1 h: 100.0%

198.B-2004(C): 1910 of 1910 OBs: 100.0%, or 199.6 of 199.6h: 100.0%

198.B-2004(D): 1040 of 1040 OBs: 100.0%, or 173.2 of 173.2h: 100.0%

198.B-2004(E): 2373 of 2374 OBs: 99.9%, or 200.0 of 200.0h: 100.0%

198.B-2004(F): 180 of 180 OBs: 100.0%, or 20.8 of 20.8h: 100.0%

198.B-2004(G): 4618 of 4658 OBs: 99.1%, or 417.1 of 420.1h: 99.3%

198.B-2004(I): 2591 of 3323 OBs: 78.0%, or 201.1 of 256.9h: 78.3%

198.B-2004(K): 70 of 3580 OBs: 2.0%, or 5.3 of 272.7h: 2.0%

198.B-2004(L): 44 of 213 OBs: 20.7%, or 3.9 of 21.5h: 18.1%

Current observations  
The 4 currently active runs G,I,K,L continue with the observations of the outer disk areas, as well as include some grade D observations. In February 2020 we will also submit the phase 2 material for 4 additional runs: M,N,O,P, to be carried out during P105, 106, and if necessary and possible P107. Run M includes 15.5 h of grade D observations, and those that were rejected by our own QC. Runs N and O will include the missing epochs for disk230, and the outer regions of disk-low, and disk-high to a total of 132 hours. Run P as not included in the VVVX proposal, but given that over the last years the winter semester (P97, 99, 101,103) always had time for less constrained observations, we were granted an additional 225 hours, which will be used to observe the inner parts of the Bulge (42 tiles) 63 times. How complete these observations will be at the time VIRCAM will be replaced by 4MOST- is uncertain at this point.

bulge-Jband-12042019

disk1-Jband-12042019

disk2-Jband-12042019

Distribution of Ks-band epochs

The following plots show the delay between two consecutive observing periods for each of the tiles in the different areas. Please note that disk+230 and the outer range of the disk-low and disk-high area have only been observed <5 times. The plots will be updated in due time.

Bulge-ori

Disk-ori

Bulge-low

Bulge-high

Disk+20

Disk-low

Disk-high

Disk+230

If you need any of the above plots, please send a request to maren551@gmail.com, the jpg files have a reduced resolution, and  I can send you the original ps files.

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