February 16, 2005
from: C. Carilli
to: J. Turner
re: DRSP and ALMA rebaseline
cc: A. Wootten, A. Blain, P. Cox, T. Wilson
Jean,
Below are some notes concerning some of the extragalactic DRSPs in the
context of ALMA rebaseline plan (64 to 50 antennas). Andrew Blain and
Pierre Cox are considering the rest of themes in 1.1 to 1.6. I have
put my notes at the end of each DRSP, starting with phrase: 'Effect of
Re-baseline:'.
Some general comments:
1. I have had some exchange with Mark Holdaway on the effect of
decreasing number of antennas on calibration capabilities. I attached
that as a separate file (I think you may have been on the cc list
already). In summary, rebaseline does not preclude standard
calibration schemes for ALMA.
2. Most programs can be 'fixed' with just increased integration time.
But, there may be a limit to this due to the onset of systematic
errors (eg. due to troposphere or electronics), ie. the noise may not
continue to decrease like root time for very long integration times.
These are impossible to predict or quantify at this stage, and in the
end, may not ever be an issue, but I point out the possibility
where relevant.
3. A few programs are dynamic range limited, in which case the
collecting area is not the issue, but the uv coverage is. Again, hard
to quantify without simulations, but again, I point out the
possibility where relevant.
4. I have one variable source program (IDVs), in which case in may not
be possible to simply increase the integration time.
That's all from me. See you in Garching.
cc
================================================================
1.1.5: Name -- Molecular line studies of submm galaxies --
constraining dust obscured galaxy formation
Authors: C. Carilli
2. Science goal: The discovery of the IR background, and the
SCUBA/MAMBO population of dusty, star forming galaxies at high
redshift, has transformed our understanding of galaxy formation. It is
now clear that a significant fraction (of order 50%) of star formation
in the cosmos occurs in galaxies that are heavily obscured by dust,
and that this fraction may rise with redshift, possibly corresponding
to the formation of spheroidal galaxies in active starbursts. One
highly uncertain aspect of the study of submm galaxies is their
redshift distribution. Optical redshifts remain problematic for the
majority of such sources, and can be misleading due to possible
mis-identifications. We propose a three part program -- (1) a 'blind'
search for CO emission from a representative sample of submm galaxies
to constrain their redshift distribution, (2) high resolution imaging
of a sub-sample to determine the gas distribution and dynamics on
sub-kpc scales and (ii) a search for HCN emission to search for dense
gas directly associated with star formation. A representative sample
of sources will be chosen from standard (sub)mm continuum surveys with
large single dishes or by ALMA itself.
Part 1: Redshift search -- I assume redshifts will be 'narrowed-down'
via photometric techniques (optical and/or radio) to +/- 0.5 in dz,
and that the typical source redshift is between 2 and 3. Using band 3
then requires 3 settings between 90 and 116 GHz to get the CO(3-2)
line. This will take about 1hr per source (see below). A second
search will then be required to look for higher/lower order
transitions to confirm the redshift. This will take another hour.
This second search will also give some indication of CO excitation
conditions. I assume the characteristic line flux density is
of order 1 mJy.
Part 2: High resolution CO imaging -- I assume the characteristic
source size is >= 1 kpc (0.2"), and intrinsic brightness
temperature >= few K.
Part 3: HCN emission is typically 10x fainter than CO.
To get a 4 sigma detection will then take of order 10hrs/source.
3. Number of sources: 50
4. Coordinates:
4.1. Any
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: small configuration preferred - (1) and (3)
A configuration for (2)
5.2. Range of spatial scales/FOV:
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 3 -- initial search, high res imaging, HCN
search
Band 6 -- 220 GHz follow-up for redshift
verification
6.2. Lines and Frequencies CO, HCN at z=1 to 5, various transitions
6.3. Spectral Resolution (km/s) 100 km/s
6.4. Bandwidth or spectral coverage: 8 GHz (for search)
7. Continuum flux density:
7.1. Typical value: 1 mJy
7.2. Continuum peak value:
7.3. Required continuum rms:
7.4. Dynamic range in image:
8. Line intensity:
8.1. Typical value: 1 mJy -- CO(3-2), 0.1mJy -- HCN
8.2. Required rms per channel: 100 GHz -- 0.14 mJy (20min), 0.026mJy
(10hrs)
-
-
-
-
-
-
-
-
-
-
- GHz -- 0.2 mJy Imaging -- T_B = 0.25 K at 0.2" res in
1hr
note: this corresponds to intrinsic
T_B = 0.9 K (1sigma) at z=2.5
8.3. Spectral dynamic range:
9. Polarization: no
10. Integration time per setting:
(1a) Search -- 1/3hr per setting x 3 settings x 50 srcs with band 3
= 50hr
(1b) 1 hr/src for verification x 50 sources with band 3 or 6
= 50 hr
(2) CO imaging -- 1hr/src x 20 srcs with band 3
= 20 hr
(3) 10 hr/src for HCN search for 5 sources with band 3
= 50 hr
11. Total integration time for program: 170
**********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
This science is not fundamentally disabled by decrease in number of
antennas. Just the integration times will have to be increased by a
factor 1.64, or we could decrease the number of sources by this
factor. Note that for the HCN search we are already at 5 sources. In
this case we would want to keep 5 sources and go to 82 hrs. For these
sources the new integration time per source is 16hrs, which may lead
to some issues concerning systematics for long integrations when
searching for faint broad lines.
**********************************************************************
1.3.1: Single DRSP
Last modified: Saturday, 18-Oct-2003 14:59:35 CEST
1. Name of program and authors
Spectral line survey in high-z molecular absorption systems
Wiklind T., Combes F.
- One short paragraph with science goal(s)
Molecular line absorption in front of a radio continuum sources
is a very powerful technique to detect even small quantities of
interstellar molecules in external galaxies. It is also
complementary to the emission technique: it samples molecules
in low excitation state, that would never have been detected in
emission. For galaxies at large distances, molecular absorption
lines offer the only way to observe rare molecular species.
This has been proven through the detection of many molecular
species (about 20) at redshifts z=0.25-0.89, using pre-ALMA
instrumentation. The sensitivity is largely determined by the
strength of the background continuum source, meaning that a
large collecting area is the main issue (the sources themselves
remain point sources even at high angular resolution).
The completion of ALMA makes it possible to make a spectral
line survey to an unprecedented level of the molecular
interstellar medium in distant galaxies.
We propose to carry on a complete molecular line survey (using the
available frequency bands) towards 3 remarkable sources at different
redshifts, in order to probe the interstellar chemistry and its
evolution. Many different molecular species, such as CCH,
C3H2,
HOC+,
SiC, deuterated species etc. are expected to be detected.
A complete spectral line survey will allow a detailed comparison
of the interstellar chemistry of these three distant sources with
that of the Milky Way ISM. In addition, the survey will include
several molecular lines which for Milky Way gas are not possible
to observe from the ground; such as the ground transition of
LiH
and water vapor, as well as the elusive molecular oxygen.
Noise rms limits have been chosen such that over most of the
available frequencies, absorption lines with depth of <1% of the
continuum flux can be detected at 5sigma. Over some frequency
intervals and for the stronger sources, this limit is set as
low as 0.15%. This corresponds to column densities of CO and
HCO+ of 910E12 and 1E10, respectively. It is possible that the
density of lines will be large, possibly limiting the detections
of individual lines through confusion over certain frequency
intervals.
We propose to do a systematic survey in the 4 priority bands
Band 3: 86 GHz - 116 GHz
Band 6: 211 GHz - 275 GHz
Band 7: 275 GHz - 370 GHz
Band 9: 602 GHz - 720 GHz
for 3 absorption systems already observed with IRAM and SEST,
and visible from Chajnantor:
PKS1830-211 (z=0.89)
PKS1413+135 (z=0.25)
CenA (z=0)
- Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's,
-
-
-
-
-
-
-
-
- T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS)
-
- sources PKS1830-211, PKS1413+135 and CenA (note that PKS1830-211 gives two sight lines through the intervening galaxy, separated by ~6 kpc).
- Coordinates:
-
- 1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus)
1830-211, 1413+135, 1325-43
Indicate if there is significant clustering in a particular RA/DEC range
(e.g. if objects in one particular RA range take 90% of the time)
NO
-
- 2. Moving target: yes/no (e.g. comet, planet, ...)
NO
-
- 3. Time critical: yes/no (e.g. SN, GRB, ...)
NO
- Spatial scales:
-
- 1. Angular resolution (arcsec):
All three targets are point sources for which the angular resolution
does not really matter.
-
- 2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...)
Single field per source.
-
- 3. Single dish total power data: yes/no
NO
-
- 4. ACA: yes/no
NO
-
- 5. Subarrays: yes/no
NO
- Frequencies:
-
- 1. Receiver band: Band 3, 6, 7, or 9
Band 3, 6, 7 and 9
-
- 2. Lines and Frequencies (GHz): (approximate; do NOT go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify e.g. "6 frequency settings in Band 3". Apply redshift correction yourself)
This is a line survey. We will cover the entire extent of each band
falling within atmospheric windows of sufficient transparency.
-
- 3. Spectral resolution (km/s):
-
- - 3 km/s
-
- 4. Bandwidth or spectral coverage (km/s or GHz):
Band 3: 2x1 GHz = 2 GHz, 1024 channels, ~3 km/s (17 tunings for entire band)
Band 6: 4x1 GHz = 4 GHz, 512 channels, ~2.5 km/s (18 tunings for entire band)
Band 7: 8x1 GHz = 8 GHz, 256 channels, ~3.3 km/s (13 tunings for entire band)
Band 9: 8x1 GHz = 8 GHz, 256 channels, ~1.8 km/s (16 tunings for entire band)
- Continuum flux density:
-
- 1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects)
Variable radio sources, Minimum 0.2 Jy, average around 1 Jy
Estimated continuum fluxes used in time calculations:
PKS1413 PKS1830 Cen A
Band 3: 0.2 2.0 6.0
Band 6: 0.1 1.0 3.0
Band 7: 0.05 0.5 2.0
Band 9: 0.02 0.2 1.0
-
- 2. Required continuum rms (Jy or K):
The continuum rms is defined as the limit in percentage of the source
continuum flux where an absorption line can be detected at 5sigma. The
values in parenthesis are the actual channel to channel noise rms:
PKS1413 PKS1830 Cen A
Band 3: 1 (0.4 mJy) 0.1 (0.4 mJy) 0.05 (0.6 mJy)
Band 6: 3 (6.0 mJy) 0.5 (1.0 mJy) 0.15 (0.9 mJy)
Band 7: 5 (0.5 mJy) 1 (1.0 mJy) 0.5 (2.0 mJy)
Band 9: 50 (2.0 mJy) 15 (6.0 mJy) 5 (10.0 mJy)
-
- 3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether e.g. weak objects next to bright objects)
no imaging is needed.
- Line intensity:
-
- 1. Typical value (K or Jy): (take average value of set of objects) (optional: provide range of values for set of objects)
in average 0.02 Jy (but can be much lower)
-
- 2. Required rms per channel (K or Jy):
See 7.2
-
- 3. Spectral dynamic range:
100
- Polarization: yes/no (optional)
no
-
- 1. Required Stokes
total intensity only
-
- 2. Total polarized flux density (Jy)
N/A
-
- 3. Required polarization rms and/or dynamic range
N/A
-
- 4. Polarization fidelity
N/A
- Integration time for each observing mode/receiver setting (hr):
Below the integration time is given as hour (per tuning/total time).
This done for each band and source. Note that PKS1413 will only be
observed using band 3 and 6.
PKS1413 PKS1830 Cen A
Band 3: 1.4/24 1.0/17 0.5/9
Band 6: 1.5/27 1.2/22 1.0/18
Band 7: 5.2/0 1.3/17 0.3/13
Band 9: 8.4/0 1.0/16 0.5/8
- Total integration time for program (hr):
171 hours + over-head
- Comments on observing strategy (e.g. line surveys, Target of Opportunity, Sun, ...): (optional)
This is a molecular line line survey. The observations are
self-calibrated using the central continuum source. The pointing
accuracy needs to be than 5". Very good weather conditions are
only required for high frequency observations.
A homogeneous sensitivity is necessary in order to allow a
comparative abundances study of weak lines.
The estimated time can be decreased by lowering the target
sensitivity or only choosing PKS1830-211 and Cen A as targets.
However, given the uniqueness of this data set, we would prompt
for a significant time allocation.
**********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
Again, this science is not fundamentally disabled by decrease in
number of antennas. Just the integration times will have to be
increased by a factor 1.64. In this case we cannot decrease the number
of sources. Since this is a line survey, the dynamic range issues for
long integrations is not an issue (ie. the program assumes lots of
shorter integrations). Since this is a line survey (lots of short
integrations at different frequencies and/or different sources),
systematics and/or dynamic range limits for long integrations are not
an issue.
**********************************************************************
1.3.2: Single DRSP
Last modified: Saturday, 18-Oct-2003 15:01:23 CEST
- Name of program and authors
A deep search for new molecular absorption line systems
Wiklind T., Combes F.
- One short paragraph with science goal(s)
Observations of molecular absorption lines offer the only way
to obtain detailed information of the physical and chemical
parameters of the molecular interstellar medium in distant
galaxies. The sensitivity is essentially only given by the
strength of the background continuum source, independent of
the distance.
Four molecular absorption line systems at redshifts between
z=0.25-0.89 have previously been detected using single dish
telescope, and allowed a detailed study of the astrochemistry
of these systems, including molecular species never before
observed from the ground. In addition, since molecular absorption
is biased towards diffuse and therefore excitationally cold gas,
the observations have made it possible to measure the temperature
of the Cosmic Microwave Background radiation at the redshift of
the absorber.
In order to make a comparative study of the chemical and physical
status of the molecular gas at earlier epochs it is necessary
to increase the number of known systems. Molecular absorption
line systems are rare, about 100 times less common than damped
Lyman-alpha systems. They are also difficult to detect since
continuum fluxes of the background sources are relatively weak at
mm/submm wavelenghts. Also, the mere presence of obscuration
means that redshift information is lacking. This was the case
for one of the known absorption systems and it was detected by
the technique of frequency scanning, looking for absorption of
high-opacity molecules such as CO and HCO+ (actually, the line
first detected in this case turned out to be a HNC(2-1) line).
By observing the frequency range 86-116 and 226-260 GHz, the
entire redshift space is covered for CO and HCO+ lines. These
are the lines with the highest opacities.
In this project we propose a search for molecular absorption
towards ~70 selected radio loud AGNs with mm continuum fluxes
greater than 50mJy. The targets will be prioritized according to
a few criteria which enhances the probability for the presence
of obscuration; such as gravitational lensing (small impact
parameter to the lens), suppressed soft X-ray flux, optically
weak and indications of reddening. In order to circumvent the
missing or uncertain redshift information, we will search for
absorption over the entire redshift range using the technique
of frequency scanning.
Noise rms limits have been chosen such that band 3, which covers
z=0-0.34 and z>0.54,m absorption lines with depth of 5% of the
continuum flux can be detected at 5sigma. In band 6, covering
z=0.34-0.54, the limits have been set to 10% at 3sigma in order
to enable a large number of sources to have complete redshift
coverage. With the velocity resolution given below, these limits
corresponds to column densities of CO and HCO+ of 710E14 and
8E11 cm-2, respectively.
- Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's,
-
-
-
-
-
-
-
-
- T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS)
-
- flat spectrum radio continuum sources
- Coordinates:
-
- 1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus)
Source list can be selected such that there is any desired spread
in RA and DEC.
Indicate if there is significant clustering in a particular RA/DEC range
(e.g. if objects in one particular RA range take 90% of the time)
NO
-
- 2. Moving target: yes/no (e.g. comet, planet, ...)
NO
-
- 3. Time critical: yes/no (e.g. SN, GRB, ...)
NO
- Spatial scales:
-
- 1. Angular resolution (arcsec):
All targets are point sources for which the angular resolution
does not really matter.
-
- 2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...)
Single field per source.
-
- 3. Single dish total power data: yes/no
NO
-
- 4. ACA: yes/no
NO
-
- 5. Subarrays: yes/no
NO
- Frequencies:
-
- 1. Receiver band: Band 3, 6, 7, or 9
Band 3 and 6
-
- 2. Lines and Frequencies (GHz): (approximate; do NOT go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify e.g. "6 frequency settings in Band 3". Apply redshift correction yourself)
The aim is redshifted CO and HCO+ lines. By using the entire
frequency range of band 3 (86-116 GHz) and part of band 6
(226-260 GHz), the entire redshift range is covered.
-
- 3. Spectral resolution (km/s):
Band 3: ~6 km/s
Band 6: ~5 km/s
-
- 4. Bandwidth or spectral coverage (km/s or GHz):
Band 3: 4x1 GHz = 4 GHz, 512 channels, ~6 km/s (9 tunings for entire band)
Band 6: 8x1 GHz = 8 GHz, 256 channels, ~5 km/s (5 tunings for 226-260 GHz)
- Continuum flux density:
-
- 1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects)
-
- sources with fluxes 50 - 100 mJy
- sources with fluxes 100 - 200 mJy
- sources with fluxes >200 mJy
-
- 2. Required continuum rms (Jy or K):
We aim at being able to detect an absorption at 5sigma at 5% of the
continuum level in band 3 and at 10% and 3sigma in band 6. For a
source with a background continuum of 100 mJy this corresponds to
a 1sigma noise rms of 1 mJy.
The continuum rms is defined as the limit in percentage of the source
continuum flux where an absorption line can be detected at 5sigma:
-
- 3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether e.g. weak objects next to bright objects)
no imaging is needed.
- Line intensity:
-
- 1. Typical value (K or Jy): (take average value of set of objects) (optional: provide range of values for set of objects)
See 7.2
-
- 2. Required rms per channel (K or Jy):
See 7.2
-
- 3. Spectral dynamic range:
100
- Polarization: yes/no (optional)
no
-
- 1. Required Stokes
total intensity only
-
- 2. Total polarized flux density (Jy)
N/A
-
- 3. Required polarization rms and/or dynamic range
N/A
-
- 4. Polarization fidelity
N/A
- Integration time for each observing mode/receiver setting (hr):
Below are integration times to reach a 5sigma rms of 5% of the
background source continuum for band 3, and a 3sigma of 10% of
the continuum in band 6. The targets are divided into approximately
10 sources with flux densities in the range 50-100 mJy, 30 sources
with 100-200 mJy and 30 sources with 100-200 mJy.
Flux 50 mJy
band 3: 0.9h/tuning, 9 tunings/source, ~9 hours/source
band 6: 1.0h/tuning, 5 tunings/source, ~5 hours/source
Flux 100 mJy
band 3: 0.2h/tuning, 9 tunings/source, ~1.8 hours/source
band 6: 0.3h/tuning, 5 tunings/source, ~1.5 hours/source
Flux 200 mJy
band 3: 0.06h/tuning, 9 tunings/source, ~0.5 hours/source
band 6: 0.07h/tuning, 5 tunings/source, ~0.4 hours/source
Average total integration times :
-
-
-
- -100 mJy: 5 hours per source, total = 50 hours 100-200 mJy: 2 hours per source, total = 60 hours >200 mJy : 0.5 hours per source, total = 15 hours
- Total integration time for program (hr):
125 hours + over-head
- Comments on observing strategy (e.g. line surveys, Target of Opportunity, Sun, ...): (optional)
Targets will be radio loud AGNs with one or more of the following
indications of possible obscuration along the line of sight (either
intervening or intrinsic) (i) optically weak or blank field, (ii)
indication of reddening, (iii) gravitationally lensed, (iv) suppressed
soft X-ray flux, (v) observed galaxy along the line of sight.
The observations are self-calibrated using the background continuum
source. The pointing accuracy needs to be than 5".
*************************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
Again, this science is not fundamentally disabled by decrease in
number of antennas. Just the integration times will have to be
increased by a factor 1.64, or they could decrease the number of
sources from 60 to 37. Again, since this is a line survey (lots of
short integrations at different frequencies and/or different sources),
systematics and/or dynamic range limits for long integrations are not
an issue.
**********************************************************************
1.6.1: Name -- High resolution imaging of radio hot spots
Authors: C. Carilli
2. Science goal: We will perform high resolution imaging at 100, 220,
and 650 GHz of the radio hot spots, and jets, of the archtype powerful
radio galaxies Cygnus A and Pictor A. These data, combined with VLA
images at 8, 22, and 43 GHz, will provide the definitive test of
particle acceleration and loss mechanisms in the hot spots (=terminal
jet shocks) of powerful radio galaxies. The required sensitivities and
dynamic ranges are extrapolated from existing 43 GHz images based on
reasonable physical models for first order Fermi acceleration, and
synchrotron radiative losses, at terminal jet shocks (Carilli et
al. 1999, AJ 118, 2581; Perley et al. 1997, A&A, 328, 12). In
particular, the 650 GHz imaging is in the critical range where an
exponential cut-off is expected due to radiative losses during the
finite shock crossing time of the electrons. These observations will
delineate in detail the regions of most active particle acceleration,
and can be used to determine hot spot magnetic field strengths and
relativistic particle energy densities, independent of minimum energy
assumptions. Observations of the inner jets will constrain particle
acceleration processes along the jet, thought to occur in oblique
(weak) shocks within the jets. Resolution must be matched to that of
the VLA observations = 0.2".
3. Number of sources: 2
4. Coordinates:
4.1. 1957+4035, 0518-4548
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 0.2"
5.2. Range of spatial scales/FOV: 0.2" to 8"
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 3 -- 100 GHz in Configuration A
Band 6 -- 220 GHz in Configuration B/C
Band 9 -- 650 GHz in Configuration D
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: standard continuum
7. Continuum flux density:
7.1. Typical value: >= 1 mJy/beam at 100 GHz
>= 0.5 mJy/beam at 250 GHz
>= 0.1 mJy/beam at 650 GHz
7.2. Continuum peak value:
Hot spots: 45 mJy/bm at 100 GHz
-
-
-
-
-
- mJy/beam at 250 GHz
- mJy/beam at 650 GHz
- Cores
- 0.5 to 1 Jy
7.3. Required continuum rms:
-
-
-
-
-
- 01 mJy/bm at 100 GHz
- 02 mJy/beam at 250 GHz
- 06 mJy/beam at 650 GHz
7.4. Dynamic range in image: 5000
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting: due to small PB, each track will
cycle through 3 pointing positions = 2 hot spots + core.
1 track (+/- 2hr) at 100 x 2 sources
1 track (+/- 2hr) at 250 x 2 sources
2 track (+/- 2hr) at 650 x 2 sources
11. Total integration time for program: 32 hr
********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
These are likely dynamic range limited observations, and hence
are not affected by the decreased collecting area. However, they
could be disabled if we find that the dynamic range limitations
are significantly reduced (ie. below 5e3) due to the worsened
uv coverage.
**********************************************************************
1.6.2: Name -- High resolution imaging of X-ray hot spots in radio
jets
Authors: C. Carilli
2. Science goal: We will perform high resolution imaging at 100 and
350 GHz of the X-ray detected hot spots in the jets of the archtype
jet sources M87 and 3C273. X-ray detected jet knots provide the most
severe constraints on particle acceleration and emission mechanisms
within radio jets, with radiative lifetimes that can be measured in
years. The spectral properties of these hot spots are well constrained
at cm, and optical to Xray wavelengths. The proposed observations will
provide the key link between the cm and optical/Xray regime, and hence
provide critical constraints on emission mechanisms (eg. synchrotron
or inverse compton) for the Xrays, as well as constraints on particle
acceleration mechanisms in the jets (see review by Harris 2003,
astroph 0302097). Resolution must be matched to that of the Chandra
and the VLA observations (0.5").
3. Number of sources: 2
4. Coordinates:
4.1. 1229+0203, 1230+1223
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 0.2"
5.2. Range of spatial scales/FOV: 0.5" to 15"
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 3 -- 100 GHz in Configuration B
Band 7 -- 350 GHz in Configuration D
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: standard continuum
7. Continuum flux density:
7.1. Typical value:
7.2. Continuum peak value:
-
- Cores
- 5 to 10 Jy
7.3. Required continuum rms:
-
-
-
-
-
- mJy/bm at 100 GHz
- mJy/bm at 350 GHz
7.4. Dynamic range in image: 10000
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting:
1 track (+/- 2hr) at 100 x 2 sources
1 track (+/- 2hr) at 350 x 2 sources
11. Total integration time for program: 16 hr
********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
As above, these are likely dynamic range limited observations, and
hence are not affected by the decreased collecting area. However, they
could be disabled if we find that the dynamic range limitations are
significantly reduced due to the worsened uv coverage. The dynamic
range limitations in this case are even more stringent, and we need to
do at least 1e4, or better in some sources.
**********************************************************************
1.6.3: Name -- The general relativistic shadow of Sgr A*
Authors: C. Carilli
2. Science goal: We propose VLBI imaging at 220 GHz of Sgr A* using
the 'Pacific array' (see note below). These observations will allow
for reasonable imaging at 20 uas resolution, well matched to the scale
of the expected general relativistic shadow of the SMBH in Sgr A*
(Falcke et al.2000 528, L13). These observations will provide the
final evidence for the existence of a SMBH at the Galactic center,
provide a fundamental test of strong field GR, and are the most direct
method for separating a Kerr (ie. spinning) from a Schwarzschild
black hole. At a minimum, the sensitivity per baseline is adequate to
perform model fitting on relatively short timescales (minutes), while
the array itself has enough antennas to provide both closure amplitude
and phases, and hence should be adequate for hybrid imaging of the GR
shadow of Sgr A*. The existence of reasonable mm-VLBI calibrators (eg
NRAO 530) in the vicinity of Sgr A* will allow for phase-referenced
fringe fitting, although the source itself is strong enough, and the
UV coverage dense enough, to allow for hybrid mapping as well. The
source Sgr A* has been detected at 220 GHz on the
PdBI -- Pico Veleta
baseline (resolution = 300 uas) with a flux density of 2.0 Jy, and an
upper limit to the size of order 100 uas (Krichbaum et al. 1998 335,
L106). The proposed observations will have more than an order of
magnitude better resolution, more than two orders of magnitude better
sensitivity, and, again, enough antennas to perform proper imaging of
Sgr A*.
3. Number of sources: 1
4. Coordinates:
4.1. 1742-2859
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 20uas
5.2. Range of spatial scales/FOV: 20 uas -- 100 uas
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E,
phased array
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI
recorder)
7. Continuum flux density:
7.1. Typical value:
7.2. Continuum peak value: <= 2 Jy
7.3. Required continuum rms:
ALMA - HHT baseline, 10 min rms = 0.7 mJy
ALMA - LMT baseline, 10 min rms = 0.2 mJy
7.4. Dynamic range in image: 1e3
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting:
4 tracks of 4hrs each
11. Total integration time for program: 16 hr
Notes: The pacific array at 220 GHz consists of: ALMA, HHT, LMT,
CARMA, and any of CSO/JCMT/SMA. We estimate mutual visibility of Sgr
A* of about 4hrs. Note that an Atlantic array might also be
considered, including
PdBI, IRAM 30m.
**************************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
The key to these observations will be to be able to perform
calibration transfer and then hybrid imaging on-source, on fairly
short timescales. ALMA provides the most sensitive element (by far)
in the Pacific array, and hence anchors the whole project, enabling
adequate (self-) calibration on short timescales. Decreasing the
collecting area clearly impacts this, ie. by decreasing the minimum
timescale for self calibration solutions by a factor 1.64. On these
short timescales, the phase errors increase roughly linearly (powerlaw
index=5/6) with calibration timescale, so a factor 1.64 could be alot
in terms of residual rms phase noise. Is this completely debilitating?
Unclear until we try, but it certainly doesn't help.
**********************************************************************
1.6.4: Name -- mm VLBI observations of core-jets
Authors: C. Carilli
2. Science goal: We propose VLBI imaging using the Pacific array (see
1.6.3) at 220 GHz of a representative sample of radio jets in low
redshift radio galaxies. These data will probe to scales of 20uas,
corresponding to 50 Schwarzschild radii at the distance of M87 (17
Mpc). Observations of M87 suggest that these scales correspond to the
fundamental regime where initial jet collimation occurs (Junor et
al. 1999 Nature 401, 891). Hence these observations will provide a key
test of jet formation models in radio galaxies.
3. Number of sources: 10
4. Coordinates:
4.1. Choose equatorial sources: Declination = 0 +/- 10deg
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 20uas
5.2. Range of spatial scales/FOV: 20 uas -- 200 uas
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E,
phased-array
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI
recorder)
7. Continuum flux density:
7.1. Typical value:
7.2. Continuum peak value: typically of order 1 Jy
7.3. Required continuum rms:
ALMA - HHT baseline, 10 min rms = 0.7 mJy
ALMA - LMT baseline, 10 min rms = 0.2 mJy
7.4. Dynamic range in image: 1e3
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting:
10 sources at 5 hrs per source
11. Total integration time for program: 50 hr
*********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
These are likely dynamic range limited observations, and hence are not
affected by the decreased collecting area. However, they could be
disabled if we find that the dynamic range limitations are
significantly reduced due to the worsened uv coverage. The dynamic
range limitations in this case are about a few thousand.
**********************************************************************
1.6.5: Name -- Imaging the molecular gas in high redshift FIR-luminous
QSOs
Authors: C. Carilli
2. Science goal: We propose high resolution (0.2") imaging of the CO
emission from high redshift (z=4 to 6.4) QSOs. Studies of high
redshift QSOs have shown that about 30% of the sources are luminous
FIR sources, corresponding to thermal emission from warm dust, with
dust masses >= 1e8 M_sun (eg. Omont et al. 2003, A&A 398, 857; Carilli
et al. 2002
ApJ 555, 625). In all cases studied with adequate
sensitivity (and redshift accuracy), CO emission has also been
detected, with typical line peak flux densities for the 5-4 transition
(redshifted to band 3 of ALMA) >= 2 mJy. Various lines of argument
suggest that the dominant dust heating mechanism is star formation,
implying star formation rates of order 1e3 M_sun/year, although the
AGN could also contribute to the dust heating. The coexistence of
massive starbursts and major accretion events onto supermassive black
holes, is consistent with the idea of coeval SMBH-galaxy formation at
high redshift, as suggested by the close correlation between black
hole mass and bulge mass seen in nearby spheroidal galaxies. Imaging
the CO emission provides the only means of determining the dynamical
mass of the host galaxy, and also provides information on the nature
and physical conditions of the earliest galaxies. In particular,
determining the distribution of the molecular gas and dust relative to
the AGN could help to constrain the dust heating mechanism, as well as
reveal complex/multiple sources, as might be expected in for
hierarchical structure formation.
We will observe a representative sample of 5 sources using band 3 in A
configuration (0.17" resolution). The typical sizes inferred for the CO
emitting regions are between 0.2 and 2". Assuming a characteristic
size of order 1" implies a typical expected surface brightness of
about 0.1 mJy/beam for a 50 km/s channel.
3. Number of sources: 5
4. Coordinates:
4.1. Choose equatorial sources from SDSS/DPSS, selected as
FIR-luminous QSOs from single-dish bolometer surveys (eg.
next generation MAMBO/SCUBA), and detected in CO emission
using LMT or GBT (or small configuration ALMA survey).
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 0.17"
5.2. Range of spatial scales/FOV: 0.17" to 4"
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 3 -- 100 GHz in Configuration A
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s) 50 km/s
6.4. Bandwidth or spectral coverage: 8 GHz (for continuum
sensitivity) with 512 spectral channels/polarization
7. Continuum flux density:
7.1. Typical value: 1 mJy
7.2. Continuum peak value:
7.3. Required continuum rms: 0.002 mJy/beam
7.4. Dynamic range in image:
8. Line intensity:
8.1. Typical value: 0.1 mJy/beam/channel
8.2. Required rms per channel: 0.035 mJy/beam/channel
8.3. Spectral dynamic range:
9. Polarization: no
10. Integration time per setting:
5 sources at 2x6 hrs per source
11. Total integration time for program: 60 hr
Notes: could be included in 1.1 or 1.5. A parallel program could be
to search for CO emission from high z QSOs, but this could also be
done with LMT/GBT. The unique aspect of ALMA is the high resolution
imaging. For some sources it might be possible to do multiple
transitions (eg. 5-4 and 6-5) within band 3 simultaneously, thereby
allowing for study of excitation gradients.
**********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
This science is not fundamentally disabled by decrease in number of
antennas. Just the integration times will have to be increased by a
factor 1.64 (note we are already down to 5 sources, so decreasing
number of sources is not an option). Also, the integration time per
source would be 20hrs, and could raise concerns about systematics
for long integrations when searching for faint broad lines.
**********************************************************************
1.6.6: Name -- mm VLBI imaging of IDVs
Authors: C. Carilli
2. Science goal: We propose VLBI imaging using the Pacific array (see
1.6.3) at 220 GHz of a representative sample of IDVs (Intra-Day
Variability). These data will probe to scales of 20uas, and test
models for coherent emission mechanisms to explain the very high
brightness temperatures inferred from the ISS (Maquart et al. 2000
ApJ
528, 623), thereby constraining physical conditions in the jet, and
perhaps study aspects of the accretion disk via the induced Compton
scattering mechanism(?).
3. Number of sources: 5
4. Coordinates:
4.1. Any
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: 20uas
5.2. Range of spatial scales/FOV: 20 uas -- 200 uas
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E,
phased-array
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI
recorder)
7. Continuum flux density:
7.1. Typical value:
7.2. Continuum peak value: <= 2 Jy
7.3. Required continuum rms:
ALMA - HHT baseline, 10 min rms = 0.7 mJy
ALMA - LMT baseline, 10 min rms = 0.2 mJy
7.4. Dynamic range in image: 1e3
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting:
5 sources at 5 hrs per source
11. Total integration time for program: 50 hr
****************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
Integration times will have to be increased. A potential problem is
that if we are trying to coordinate the VLBI imaging with the
luminosity state of the IDV, then we do not have the luxury of
adjusting the integration time.
**********************************************************************
1.6.7: Name -- Search for flat spectrum mm-loud AGN
Authors: C. Carilli
2. Science goal: We will search for flat spectrum, mm-loud AGN. The
search can be piggy-backed on the standard pre-observation calibrator
searches using band 3 during normal observations. A follow-up snapshot
survey (1 min/source) will then be done at 220 GHz of 1000 candidate
sources, and at 22 GHz with VLA, to determine the cm to (sub)mm
spectra of the sources. The search could reveal new population of
faint blazars, IDVs, HFPs, and other types of known sources at more
than 10 times deeper levels that is currently possible (and at higher
frequencies; Corray et al. 1998 AJ 115, 1388; Dellacasa et al. 2001,
A&A Supp), as well as possibly reveal new classes of sources, such as
very young radio jets. These can then be studied further at X- and
Gamma-rays, as well as using mm-VLBI, and standard monitoring
programs.
3. Number of sources: 1000
4. Coordinates:
4.1. Any
4.2. Moving target: no
4.3. Time critical: no
5. Spatial scales:
5.1. Angular resolution: any (small configuration preferred at 220
GHz)
5.2. Range of spatial scales/FOV: any
5.3. Single dish: no
5.4. ACA: no
5.5. Subarrays: no
6. Frequencies:
6.1. Receiver band: Band 3 -- piggy-back on standard calibrator
pre-observation search program
Band 6 -- 220 GHz follow-up
6.2. Lines and Frequencies
6.3. Spectral Resolution (km/s)
6.4. Bandwidth or spectral coverage: full
7. Continuum flux density:
7.1. Typical value: 10 mJy
7.2. Continuum peak value:
7.3. Required continuum rms: 100 GHz -- standard sensitivity for
calibrator search
220 GHz -- 0.1 mJy
7.4. Dynamic range in image: 1e3
8. Line intensity:
8.1. Typical value:
8.2. Required rms per channel:
8.3. Spectral dynamic range:
9. Polarization: yes
10. Integration time per setting:
1000 sources at 1min/source at 220 GHz
11. Total integration time for program: 20 hr
***********************************************************************
Effect of Re-Baseline: Going from 64 to 50 antennas
This science is not fundamentally disabled by decrease in number of
antennas. Just the integration times will have to be increased by a
factor 1.64, or we could decrease the number of sources by this
factor.
**********************************************************************
'>
Previously, I reviewed much of the Galaxies and Cosmology, in particular
'>
the high z stuff. I'd be happy to go over these in context
'>
of descope 1.1 to 1.6.
'>
perhaps Dr. Blain would assist?
'>
'>
in terms of decreasing number of antennas, a key point will be
'>
calibration -- what are fast switching timescales and slew distances
'>
that will be required given the lower instantaneous sensitivity?
'>
'>
cc
'>
Fast Switching was originally concieved of with the MMA, 40 8m antennas.
It basically worked. Going to 64 12m antennas actually didn't improve
fast switching's efficiency by a great deal --
consider these numbers (derived from 64 x 8m antennas):
@ 345 GHz (with appropriate conditions given dynamic scheduling
-- not the best, not the worst):
... for the "median" calibrator source, the time required to
sufficiantly detect that calibrator at 90 GHz is 0.28 s;
that calibrator is 80 mJy, and is located 1.4 deg away. The time
required to MOVE (roundtrip) is about 3 s. SO, the phase errors
we make and the efficiency that is lost due to cal time is dominated by
the MOVE time.
(If we don't calibrate at 90 GHz, but 345 GHz, a simpler observing
strategy, we need slightly more time on a more distant and somewhat
fainter calibrator: 60 mJy, 2.2 deg away, 2x slew time is 3.7 s,
and the integration time is 0.54 s -- we are still dominated by
the move time.)
My interpretation: we have a LOT OF SLACK in the system --
we can live with a) the sky not having quite as many calibrators
as the model suggests, or b) ALMA not being as sensitive as we hoped,
or even c) not having as many antennas as we wanted, and the end
result will be nearly as good as the 64x12 result. ie, I estimate
the change in overall eficiency will be less than 1% -- going
from 85% efficient, say, to 84.6% (these numbers are pure guesses).
ONLY if we are observing at 650 or 850 GHz and we are not calibrating
at 90 GHz, but at the observing frequency, does the calibrator integration
time become comparable to the slewing time to and from the calibrator.
IN THIS SITUATION, reduction in antenna number will result in a modest
increase in the integration time on the calibrator, which will be felt
modestly in the final fast switching efficiency (perhaps 1%, perhaps
more). HOWEVER, this is a really spongy mathematical system with
many degrees of freedom (OK, we'll go just a little further out to
find just a little bit brighter source and we'll integrate just a
little bit longer, and we'll trade off that slight decrease in
decorrelation efficiency by increasing the cycle time just a bit
to increase the time efficiency.... you get the picture -- there
are many dimensions to compensate when one of the assumptions
sours a bit).
When we went to 64 x 12m antennas, fast switching did not drastically
improve over 40 x 8m. Therefore, going to 50 x 12m won't drastically
decrease our phase calibration ability.
My 2 cents: these calculations WILL be performed again, sooner or later;
I actually had an error in the source counts code, which UNDERESTIMATED
the number of sources; there will be other reasons to redo the calc.
When enough reasons pile up, we'll redo the calcs using 50 x 12m
and the other "improvements in our modelling of reality". Is now that
time? I say no, what do you say?
-Mark
--
AlWootten - 21 Feb 2005